DR. FREAS:  Thank you, Dr. Linnen.  Our next Open Public Hearing speaker is Dr. John Saldanha from Roche Molecular Systems.

          DR. SALDANHA:  Thank you.  I am an employee of Roche Molecular Systems and we make the AmpliScreen test and the MPX Multiple NAT assay.  I would like to thank BPAC for giving me the opportunity to present some data.  What I am going to show you are the results of the clinical trials we have done specifically for Hepatitis B virus.

          So, these data were published by Sandy Linants in Transfusion last year.  And these were the results of the Roche AmpliScreen HBV test which was done under and IND and also post-licensing.  The test was licensed in April, 2005, so, initially, we ran the test under and IND from August 2002 to April 2005 and then, additionally, routine testing from April to December last year.

          In total, over 3,300,000 samples were tested and there were seven samples that were NAT-reactive.  These samples were all surface-antigen-negative and anticore-negative.  But I must say, at this point, this was pre-PRISM testing so none of these samples were tested on the PRISM with the U.S. cutoff.

          Of the samples, four of them remained surface-antigen-negative after they were retested on the PRISM when the PRISM assay was available.  So, out of the seven samples, four remained antisurface-antigen-negative.

          The second clinical trial we did was for the MPX test.  This is the Roche automated platform for multiplex screening.  It is a multiplex test for HBV, HCV, HIV-1 group MNO and HIV-2.  The clinical result was done in 2005 and, during the studies, over 62,000 samples were tested in pools of six and over 9,000 samples were tested individually.  I should point out that the test, according to the package insert, we recommend the testing in pools of six or individually and the usual format here is in pools of six.

          One sample was picked up in a pool of six and was shown to be HBV NAT-reactive.  It was negative on the COBAS AmpliScreen when tested in pools of 24.  And it was both PRISM, anticore and Hepatitis B surface-antigen-negative.

          So, looking at the total yield data that we have for both the AmpliScreen and the MPX, these are in U.S. donors, there were a total of eight donations of which five were missed by the PRISM.  In the second column, you can see the quantitation that was done.  I have actually put it in IUs as well because this is what the FDA are looking at for the cutoff so I think it is easier to translate.

          And I draw your attention to Sample No. 2 which had a relatively high Hepatitis B yield which is about 720 IU/ml and had a very low PRISM cutoff.  The other three samples were below the level of quantitation which is about 40 IU/ml.

          Then, looking at the follow-up, we had three donors who we could follow up and I think, in most of these cases where the Hepatitis B titer is very low, it is essential to follow up in case of false-positives.  There was one donor, Donor No. 7, who had a very high anti-HBsAg titer of 2,340 mIU/ml and this was clearly a breakthrough case. 

          One donor, Donor No. 2, was nonreactive for antisurface and this was a window-case donation so that the donor had a very high copy number, was followed up for 177 days and the first donation that seroconverted to surface antigen was after 14 days.  The anticore converted after 28 days and the antisurface came up after 14 days as well.  The donor remained DNA-positive for 21 days after the index donation.

          The second donor who was what we think is a breakthrough was followed for 167 days.  They were non-reactive for surface antigen throughout the follow up and nonreactive for antisurface as well.  But the anticore did come up positive and they were positive for DNA for up to 22 days.

          The third, that was very odd because they were followed up 59 days and they were nonreactive for all the serological markers.  We think was a low-level chronic carrier without any serological markers.  So we had the full range of donors here.  We had a window case, a breakthrough and a chronic carrier for Hepatitis B.

          So, looking at the overall rates, if we just look at the COBAS AmpliScreen data, and these were tested in pools of 24, the rate is 1 in 844,000.  These are excluding all the PRISM positives.  With the MPX, is it 1 in 72,000.  This, I think, is not a rate that we should look at because we only tested 72,000 donations.  The n number is not very high, so I realize that is probably not accurate at all.  And, if we combine all the data to get the yield for Hepatitis B in the U.S., it works out at about 1 in 690,000.

          The other bit of data that I would like to show you are data that we have done from some of our studies overseas.  This is really to show you the power of the test in picking up window-period donations.  As I said, we picked up one in this study.

          We did studies in Thailand and we tested about 240,000 donations.  Of these, 27 donations were negative for surface antigen and core using the PRISM to give a yield of 1 in 8,500 which is very high.  But this assay was able to pick up window-period donations.  And, again, going back to the discussion we had on the cutoff of 100 IU/ml, I think this seems a reasonable cutoff because the PRISM assay, I think the cutoff for that is between 200 and 300 IU/ml so it make sense to have the cutoff lower than that.  Otherwise, there is no point in doing NAT if it is set at that level.

          Finally, I would like to thank the people from Puget Sound Blood Center who generated most of the data.  This is Mark Destry, Sandy Linants and Carol Taylor.

          Thank you.

          DR. FREAS:  Thank you, Dr. Saldanha.  Our next Open Public Hearing speaker is Dr. Steve Kleinman representing the AABB.

          DR. KLEINMAN:  Thank you.  I am here today as a consultant to AABB so I have a financial arrangement with them and I will be reading a statement of that organization, but, just for full disclosure, I have done consulting work for both Chiron and Roche both of whom make NAT assays.  I don't think that influences this statement, however.

          This is a joint statement signed onto by both AABB and American Red Cross.  I will read the statement.

          Over the past several decades, there has been progressive reduction in the risk of transmission of HBV by transfusion based on the use of HBsAg tests with increased sensitivity and widespread use of the HBV vaccine.  However, on the basis of modeling studies, HBV remains the most common clinically important viral infection transmitted by transfusion with residual-risk estimates several-fold greater than those for HIV and HCV. 

          The recent FDA licensure of two manufacturers' automated triplex NAT assays, used either in minipools of 6 or 16 donations or for testing individual donations, may offer an opportunity to further reduce this risk.

          Both licensed assay systems appear to perform adequately in terms of analytical sensitivity and specificity and, when applied to contemporary U.S. donors, they generate incremental yields of 1 in 300,000 to 1 in 600,000 HBV DNA-positive donations not detected by current serological tests.  This rate is similar to the yield rate of HCV minipool NAT and substantially higher than that for HIV minipool NAT.  The HBV yield donations tend to contain low copy numbers of HBV genome that are not detected by currently available ultrasensitive surface-antigen assays.

          It has been shown, as we have talked about all morning, that these HBV yield donations include two sample types.  First, there are sero-negative window-period donations in unvaccinated donors that are likely to be infectious.  Such window-period donations have been found at a rate that is similar to that predicted by modeling. 

          Secondly, and unexpectedly, at least half of the NAT yield donations identified in all of the U.S. clinical studies represent subclinical infections in vaccinated individuals characterized by HBV DNA in the presence of low titers of anti-HBs.  Acute HBV infection in these individuals occurred years after vaccination predominantly through contact with their sexual partner who was a chronic carrier.

          The possible finding of vaccinated HBV NAT yield donations was not included in the models and infectivity of these additional yield samples is unknown.  Understanding the infectivity through the transfusion mechanism of these vaccine breakthrough NAT yield cases is critical.  It appears that the HBV minipool NAT yield rate is higher than expected as a result of the widespread use of HBV vaccine and the result in detection of these vaccinated individuals.

          Of the yield donations presented in the Red Cross study, and that was 3.8 million screened donations, two-thirds of these, or six of nine, were vaccine breakthrough cases all of which were detected by minipool NAT using a pool size of 16.  The total yield of the study was nine HBV DNA-positive donors of which eight, or close to 90 percent, were detected by minipool NAT with a single ID NAT-only donation not detectable in any pool size--that is, 4, 8 or 16.

          The data suggest that the efficient detection of the vaccine breakthrough cases by minipool NAT is likely related to a low level or a prolonged viremic phase.  Modeling studies indicate that maximum yield of HBV window-period donations can be achieved only through the use of ID NAT.  In contrast, the clinical studies conducted have shown that the majority of HBV NAT DNA-positive yield donations were detected by minipool NAT.  Thus, the adoption of minipool NAT will offer an incremental improvement in HBV transfusion safety by the detection of serologically non-reactive donations from donors with acute infection whether they were previously vaccinated or naive.

          At the present time, neither surface antigen nor anticore testing can be eliminated since these tests continue to detect donations that HBV NAT fails to detect.  Parenthetically, I will say we didn't see that data today, but it is well known and it has been presented in the past.  It is possible that eventually HBV NAT may displace one of these serological tests but this will require additional large studies.

          In summary, HBV minipool NAT is now available in multiplexed automated NAT screening formats and these tests are able to detect a number of HBV DNA-positive individuals.  Such expanded screening will have unknown clinical benefit.  In addition, its use cannot be offset by the discontinuation of any current testing.  Widespread adoption of HBV minipool NAT is predicted to occur in the future, in part as a consequence of the operational advantages of the fully automated triplexed NAT systems.  The Roche automated system is already only available as a triplexed assay and we expect that, over time, the same will be true of the Chiron system.      Based on these considerations, it is reasonable for FDA-licensed blood establishments to implement HBV minipool NAT on a voluntary basis until the FDA mandates such testing.  This mandate should be consistent with FDA-approved labeling of the two manufacturers' test that allows NAT in minipools of up to 6 or 16 donations.  There is no benefit to smaller minipool sizes from either modeling studies or clinical trials.

          We oppose a mandate for ID NAT at this time due to the relatively small increased yield observed in the Red Cross study--only one out of the nine cases--increased donor deferral and donation loss due to false positivity and logistics of a 6- to 16-fold increase in test volume and cost.   We, as an industry, recognize the potential benefit of minipool for HBV and, therefore, believe that this test should be adopted.

          As a final comment, the absence of effectiveness reimbursement mechanisms by which hospitals can recover the increased cost of blood-safety initiatives implemented voluntarily or after an FDA recommendation remains a serious flaw in the regulatory process.  HBV NAT is an example of such an initiative that will come as an unfunded mandate if FDA recommends its use. 

          Thank you. 

          DR. FREAS:  Thank you, Dr. Kleinman.  Our next Open Public Hearing speaker, Glenn Mones, representing the National Hemophilia Foundation.

          MR. MONES:  My name is Glenn Mones.  I am pleased to address the committee as a representative of the National Hemophilia Foundation.  NHF is the oldest and largest organization representing individuals affected by bleeding and clotting disorders many of whom are also affected by complications caused by tainted blood products prior to the implementation of the safety standards we have today

          NHF has historically supported and continues to support an approach to blood, blood and plasma-derived products and tissue safety that errs on the side of maximum safety.  We believe that, whenever the ability exists to improve the margin of safety, even incrementally, the imperative to protect all recipients of these products outweighs cost concerns and other issues.

          Based on this attitude, NHF has long supported broad use of NAT testing.  NHF's Medical and Scientific Advisory Council, composed of many of the countries leading medical professionals treating bleeding and clotting disorders addressed this in MASAC Recommendation 187, MASAC recommendations concerning the treatment of hemophilia and other bleeding disorders, approved by MASAC on November 15, 2008 and adopted by the NHF Board of Directors on November 16, 2008. 

          In Subsection B(3) of Section 2, Recommendations to Manufacturers of Coagulation Products, the document states that, "Nucleic acid testing offers significant incremental sensitivity over the HIV antigen test and serological tests for HIV, HCV and HBV.  This can best be accomplished by testing individual donors or very small donor minipools."

          In Section 3, Recommendations to the Food and Drug Administration, the document goes on to say that, "The Food and Drug Administration is responsible for regulating the manufacturers of coagulation products to ensure that licensed products are safe and effective.  Many of our recommendations for manufacturers should be regulated proactively by the FDA."

          Although these recommendations are aimed primarily at the specific products used most commonly by individuals with bleeding disorders, we believe they can and should be applied broadly to blood, plasma and tissues.

          NHF supported broad use of NAT testing before the existence of the newer and very practical multiplex tests.  We supported broad use before we learned what we now know about breakthrough infections and the potential for additional transmissions through blood, plasma and other donations.  We believe the time is right to implement this added measure of safety by mandating this test for all donations and, thereby, further protecting all individuals who rely upon them.

          We thank the committee and the agency for taking up this important issue and for allowing us to speak today.

          MR. FREAS:  Thank you very much, Glenn, for your presentation.

          MR. MONES:  Thank you.

          MR. FREAS:  Our next speaker is Dr. Susan Rossman from the Gulf Coast Regional Blood Center.

          DR. ROSSMAN:  Thank you.  I have no personal financial interests but I have done clinical trials for both Roche and Ortho at my center.  I am representing today the 74 members of America's Blood Centers, ABC.  We provide about half of the volunteer blood supply in the United States.  Our U.S. members are not-for-profit community-based organizations that are licensed and regulated by the Food and Drug Administration.  Hema Quebec, our Canadian member, is regulated by Health Canada.

          We thank FDA and BPAC for the opportunity to comment on the possible recommendation for use of HBV NAT for blood-donor screening.  I want to remind you that we already use two serologic assays for the screening of blood donors for HBV, one, extremely sensitive for the detection of HBsAg that is well correlated within infectivity, and one, much less specific for antibodies to the core antigen of HBV.  This assay does not correlate well with infectivity but removes most individuals that have had a past HBV infection.

          Interestingly, the potential recommendation for the performance of NAT for HBV represents a new paradigm for blood-donor screening for infectious diseases.  We are being asked to screen blood donors because new tests became available not because we are confronting an epidemic with substantial risk of transmission to blood recipients as has happened with HIV or West Nile virus.

          The move from evidence-based decision-making to an unattainable zero-risk blood supply is a source of great concern for our members.  Previous BPAC and the Advisory Committee on Blood Safety and Availability meetings addressed assay sensitivity of minipool NAT for HBV DNA and concluded that its contribution to blood safety was limited and did not justify implementation.  Only individual donor NAT appeared to increase the yield of detection of infected donors. 

          Actually, Robin Biswas from CBER FDA is the first author of a quite elegant paper we have heard about today from Transfusion indicating that sensitivity of minipool NAT was similar to that of current serological assays.

          More recently, clinical trials using one of the multiplex assays were carried out by the ARC and we have heard about that also today.  As described in the AABB statement, ARC identified nine donors with low viremia and low levels of anti-HBs among 3.8 million donations.  Several were considered breakthrough infections in vaccinated individuals.

          As mentioned in the briefing document prepared by FDA, there is no evidence that units collected from these donors are infectious.  The only way to document infectivity would be experimental attempts to infect non-human primates.  Considering the current restrictions, it is unlikely that these experiments will be ever carried out to clarify this question.

          Essentially, manufacturers bundle the three tests in response to users' hopes for operational simplicity and reduced cost not because of an epidemic or a recognized need for higher sensitivity of specificity of existing assays.  We have been told by the assay manufacturers that an FDA recommendation increases the value of the kit and will lead to price increases.  In addition, a recommendation for HBV NAT will force laboratories in our member centers using the FDA licensed HIV HCV NAT assays to move to the combined assays for HIV, HCV, HBV.  We are not convinced by the data that has been presented that this change will significantly improve safety for the recipients.

          Finally, we do not understand the recommendation for a minimum sensitivity of 100 IU/ml individual samples as suggested by Question 3.  It is an arbitrary number that is not based on data.  We agree with the AABB statement indicating that reduction of pool sizes short of individual NAT is impractical and will not significantly increase the sensitivity of the combined assays.

          ABC members suggest that implementation of NAT for HBV be a decision made between blood centers and their local medical community.  They can assess the importance of HBV in their communities and know best how to allocate the resources they have available.

          Thank you very much for the opportunity to present. 

          DR. FREAS:  Thank you, Dr. Rossman.  Our final Open Public Hearing speaker is Corey Dubin representing the Committee of 10,000.

          MR. DUBIN:  Good day, Mr. Chairman, members of the committee.  I am the President of the Committee of Ten Thousand.  We have been in this process--this is our 20th year and we are glad to still be here.  It is important to state that the Committee of Ten Thousand takes no grants or dollars of any kind from the manufacturers of biologics, drugs or medical devices--i.e., no FDA-regulated agencies.  And I, personally, have no interest, no stocks, none of that.

          That said, as you asked us to do that, Bill, I think it is not about zero risk.  It is about the precautionary principle.  I stand before you co-infected with HIV and hepatitis.  Luckily, I am surviving and I am thankful to be that. 

          What concerns us today is that you all get disconnected from us again.  There was a time when you were disconnected from us and we heard similar things.  Now, I am not comparing this discussion to HIV.  That is not my goal for a moment.  But I am stating the importance of the connection between this committee and us, the end users.  When I say "us," I don't mean hemophilia because, when I think about the issue before us today, I think more about our other constituency at the committee, immune-compromised people, HIV-infected people, who depend frequently on blood components.  Neonates come to mind when you talk about blood components and the risk there.

          For us, it is the precautionary principle that is important.  We are not suggesting this is an epidemic but we are suggesting that this is another step that takes us to another degree of safety.  We are not unmindful to the cost to the blood community.  We are also supportive in our work on the Hill.  We discuss with Congress regularly the need to full-fund reimbursement, not just for our own community but for those of you in the blood community and elsewhere, community clinics, DISH hospitals who are all having trouble surviving.

          But FDA's task is not cost.  It is safety.  And the last time it was cost, we had heard.  And we want to remind you that this is also a period when what we were told for years as a theoretical risk in terms of transmission is now a probably risk, vCJD.  And we are waiting for more information from the British case to understand the ambiguity and how to weigh that risk and what it means.

          But there is no question the community is nervous about that.  So I think it is important to understand, we know better than zero risk.  There is no such thing, and to try and attain it would probably break the bank for many of these people sitting in the room.

          The precautionary principle is something different.  So I think it is most important that we remind you of that and that you all, as I began my statement, remember us.  We are not all gone yet.  There are enough of us still here to know what happened and understand the importance of the precautionary principle.

          And I would say, even more important for me, personally, having sat on this committee two terms, is the relationships we all built.  We learned from each other and the committee had a connection to what my friend calls "those with an arm in the game."  We have an arm in the game.  You make recommendations that impact us 24/7 every day.  And I am using the larger "us," not just hemophilia-- von Willibrand's--but even the neonates I mentioned, those with HIV and other immune-compromised disorders like primary immune deficiency and others.

          Those are the people we all must remember because, when I hear the numbers are low, and I understand they are, I still know the families who get hit, who shoulder this.  Remember, even if they are low numbers, there is a family out there that is going to shoulder this.  Can we prevent it?  Not always.  Can we do our best to contain risk?  We believe we can, and you can.

          And so we would remind you of that and, as always, thank you for the opportunity to address you.

          MR. FREAS:  Thank you for your comments, Mr. Dubin.

          DR. SIEGAL:  Let's proceed with the knowledge that the cafeteria closes at 2 o'clock and so we should be as judicious as we can.

                Open Committee Discussion

          DR. SIEGAL:  We are now going to open the committee discussion concerning blood-donor screening for Hepatitis B by NAT.  We will take questions for the committee first and then the discussion.

          DR. BISWAS:  Thanks, Bill.  Question No. 1; does the committee agree with FDA that units from donors with apparent vaccine breakthrough HBV infections, HBV NAT-positive and anti-HBs-positive, should be presumed infectious pending further studies?

          Question 2; please comment on the value and design of candidate studies using animal models to assess the infectious potential of units from Hepatitis B-vaccinated donors with breakthrough Hepatitis B infections.

          Question 3; considering the estimated yield of HBV infection, infected window-period donations and the answers to Question 1, please comment on the benefit of routine screening of blood donors for HBV NAT if testing were performed using available licensed tests on minipools assuming a sensitivity of at least 100 IU/ml for individual samples.

          DR. SIEGAL:  So, commentary?  Questions?  Discussion on Point 1?

          DR. NELSON:  It seems like only one of those are questions.  There is a yes or no, and then there are two comments.  I am confused.

          DR. SIEGAL:  Dr. Epstein. 

          DR. EPSTEIN:   Kenrad, you are not confused.  That would be rare.  No; Question 1, we want a yes/no answer and the other two are essay questions. [Laughter.]

          DR. SIEGAL:  Maureen.

          DR. FINNEGAN:  I would like to suggest that we don't have enough information to answer Question No. 1.  I don't think anybody has enough information to answer Question No. 1 because nobody has looked at the recipients of this blood to see what is going on.

          The other thing I would say is that number of non-vaccinated personnel in North America is decreasing with time and so, actually, the question you are going to be asking in ten years is breakthrough infection in a vaccinated donor, what does it do in a vaccinated recipient.

          DR. HOLLINGER:  I think, also, if you look at that first question, I agree with you.  I think, in this particular case, there is not much data to look at that particular issue.  The only one was that study by Gerlich in which there was a vaccinate individual who was vaccinated with regular vaccine after three years seroconverted to anticore with a different genotype, a different genotype to the vaccine, one which is an AYW3 subtype, not the ADW2 which makes up the vaccine.

          That platelet-pheresis donor ran from 3 to about 20 genomic equivalents per ml over a period of time.  And then they did a lookback of 65 recipients, none of whom had infection.  That is the only one we have there.  We have several other studies which, at least in my opinion, has clearly not shown any clinically relevant disease, if any disease at all, in patients who were anti-HBs-positive either in the absence of anticore and, in some cases, in the presence of anticore.

          So we do have that data also.  The other ones that were brought out that may have had some relevance were people--were donors who were anticore and anti-HBs-positive and, therefore, would be eliminated, or the recipients of those were immunocompromised individuals, stem-cell recipients, that may have had an occult infection underneath and were not tested.  So we don't know whether that one individual in the WHI [ph] study might have been an occult infected patient who, then, generated infection.

          So, anyway, I think those are the issues we have when we come to answer this question about relevance in this case.

          DR. SIEGAL:  Dr. Colvin.

          DR. COLVIN:  I keep thinking about the first question again.  We also have to consider, including it was an interesting point, I think, about the recipients who will all be vaccinated in the future.  However, when you start thinking about who are the bulk of the population who will be receiving blood or blood products, even if they were, first of all, vaccinated, many of them will be immune-compromised for other reasons, so we don't know how well their immunity will hold up against HBV.

          Second of all, a lot of recipients that we will be thinking about in this case, of course, the pediatricians will think of all the neonates who will not have been vaccinated yet.  And I think they are, again, in a particular high risk to progressing to chronic Hepatitis B infection.

          DR. HOLLINGER:  Let me just ask the question, why wouldn't they be vaccinated?

          DR. COLVIN:  The neonates?

          DR. HOLLINGER:  Yes.

          DR. COLVIN:  Well, they wouldn't have an immune response yet in the time that, say, they are perinatally getting transfused.

          DR. HOLLINGER:  But they would be vaccinated, in this country.

          DR. COLVIN:  Well, the question is, I don't--not being a pediatrician, myself, but in the NICU, is it normal practice, then, to vaccinate on Day 1 of life?

          DR. HOLLINGER:  It is practiced in this country for universal immunization with a birth dose in the vast majority of cases; yes.

          DR. COLVIN:  But just having gone through this again recently, I can tell you that, at least a lot of times they are putting it off within the hospital because the local pediatricians now are giving them multivalent vaccines for multiple things.  So they are not sure what the primary-care doc is going to do with them.  So, a lot of times, it is actually put off from the birth dose as well.

          If you are thinking about the immune response, well, how long is it going to take this other immune response to develop after a vaccination especially in a neonate who may be in the NICU who may also require blood products.

          DR. SIEGAL:  Dr. Alter, first.  Then Dr. Kulkarni.

          DR. ALTER:  I just want to remind you that, if we knew the answer to this question, there wouldn't be a question.  So we have to make a presumption at this time and we could presume that the units are infectious or we could presume that the units are not infectious.  But, to presume that they are not infectious is a risky presumption in case they turn out to be infectious.

          To assume they are infectious obviates the risk but it means that, at some point, you may have to renege what decision you make today.  But, the precautionary principle, again, would say, the presumption that the units are infectious is the safest way to go until we find the answer.  And the second question would be how can we find the answer. 

          So that is my perspective.

          DR. SIEGAL:  Dr. Kulkarni and Dr. Cryer.

          DR. KULKARNI:  As a pediatric hematologist, I think I can address some of the issues which come up.  As far as neonates are concerned, you are assuming that these are full-term neonates.  A lot of them are premature neonates.  If I have a baby with intracranial hemorrhage as a result of a bleeding disorder or whatever it is, that neonate is going to get blood and blood products before any vaccination is even considered.  So a lot of them are at risk.

          The other thing I worry about is patients who receive repeated transfusions so, in their own lifetime--for example, patients with sickle-cell disease, every three weeks they get a transfusion.  And I don't think we have an answer, is there an additive effect of repeated transfusion or repeated dosing of this particles.

          I think, having worked with the CDC and still working with them--I think an ounce of prevention is better than any cure.

          DR. SIEGAL:  Henry.

          DR. CRYER:  I am very comfortable with the precautionary principle.  I will just comment that, in my hospital, the vast majority of people who get blood transfusions are, in some way, impaired immunologically.  So, I wouldn't know if they were pre-vaccinated, whether that would do them any good or not.  I really don't know.

          The data would seem to at least suggest that, if you can get breakthrough here, that those people would be even more sustainable to breakthrough.  So I think the precautionary principle makes sense.  The problem I have with it is you are never going to know because, if we remove all those units from the blood supply, we don't have the ability to go back and find out what happened to people who might have gotten units like that before.

          We are never going to really know whether this was a real problem or not, at least from anything I heard today.  I didn't hear any experiments that would give us the answer. DR. SIEGAL:  Any other comments on the great unknown?  Jay?

          DR. HOOFNAGLE:  Why do you just propose it, and those with vaccine breakthrough opposed to everyone who is NAT-positive surface-antigen-negative?  And I kind of agree with Harvey.  You have to presume they are positive.  But I have to admit that you haven't presented any data yet that they are, and that is the problem and it leads to the second question, and is--chimeric mouse models are perfect and will answer to the study the some extent.

          Of course, if they are negative, we won't answer it completely but if you can transmit Hepatitis B to the chimeric mice or chimpanzees with one of these units that occurs 1 in 200,000, very rare, then it is reasonable to say, yes, these are infectious and press forward.  But that clearly needs to be done.

          DR. SIEGAL:  And the chimeric mouse model is more reflect of the immunocompromised host, probably, than--the chimeric mouse model is closer to the compromised host than the immuno-competent chimp.

          DR. HOOFNAGLE:  As Harvey points out, it is just a transmission model.  You are not going to get antibodies or immune responses.

          DR. SIEGAL:  That's right.

          DR. HOOFNAGLE:  But you will show that something is infectious.

          DR. SIEGAL8:  Yes; in a SCID mouse.

          DR. HOOFNAGLE:  You don't have a good tissue-culture model that you can screen this blood and that blood for.

          DR. ALTER:  I have to agree with Jay agreeing with me.

          DR. SIEGAL:  So we have a consensus.  Any other commentary?

          DR. BALLOW:  I just wanted to ask my colleague at the end of the table, what is the data on sickle-cell patients?  Do they have an increased incidence of hepatitis through blood transfusions, Hepatitis B?

          DR. KULKARNI:  I don't think we know that.

          DR. BALLOW:  Wouldn't that come to light, though?  Wouldn't that data come out just from those patients acquiring the infection?

          DR. KULKARNI:  I have no idea.  I mean, clearly, for thalassemia and for sickle cell, for multiply transfused patients, that is the risk and I think that is what the CDC study is trying to determine as we speak on the thalassemia patients.  And we are working with NHLBI to do a similar surveillance on the sickle-cell population.

          DR. HOOFNAGLE:  Among 88 sickle patients that we saw who were adults, one had chronic Hepatitis B and about three had chronic Hepatitis C.  So, yes; they get these infections.

          DR. BALLOW:  But do we know how they acquired it?  Did they acquire it through the transfusion or did they acquire it by some other means?  It is probably not known.

          DR. HOOFNAGLE:  Well, I assume it is transfusions from a long--these are adults, so transfusion from a long time ago.  They are now vaccinated, of course.

          DR. SIEGAL:  Dr. Finnegan.

          DR. FINNEGAN:  I recognize this is not part of the FDA's mandate, but I am wondering--I think Dr. Hollinger brought up that this may be a public-health issue with the vaccination of Hepatitis B and perhaps this information should be passed on to the CDC so that it could, in fact, be looked at because I think that is the question that we have brought up today, is not so much the blood supply as it is, perhaps, the issue of the vaccination.

          DR. SIEGAL:  All right.  Any other commentary before we vote on Question 1?  Will you please explain to us all what we are supposed to do with these little buttons.

          DR. FREAS:  I have never voted as a group before.  However, we will push simultaneously No. 1 if the answer is yes, No. 2 if you believe the answer is no, and No. 3 if you want to abstain.  And would you make sure you have picked your remote.  It should have your initials on the back.

          We are ready to call for the vote. 

          [Simultaneous voting.]

          DR. FREAS:  Can we see what modern technology can do for us?  For the record, we have: Dr. Nelson voted yes; Dr. Colvin, yes; Dr. Glynn, yes; Dr. Hoofnagle, yes; Dr. Trunkey, yes; Dr. Zimrin, yes; Dr. Hollinger abstained; Dr. Bower, yes; Dr. Siegal, yes; Dr. Ballow, no; Dr. Blackwelder, McComas, Cryer, Kulkarni, all voted yes; Dr. Di Bisceglie voted no; Dr. Rentas voted yes; and Dr. Finnegan abstained.

          Are those votes correct?  I've lost faith in technology for being simpler, but--

          DR. SIEGAL:  Well, I guess it worked.  Let's proceed to Question 2 which is commentary, and this doesn't require a vote, I understand.  So who would like to comment on Question 2.

          DR. FREAS:  Could we have the tally of that vote?  There were 13 yes votes, there were 2 no votes and 2 abstained.

          DR. SIEGAL:  Okay.  Let's proceed.  Commentary on Question 2.  Dr. Cryer.

          DR. CRYER:  I mean, I think it is a fascinating experimental model but I just don't see any way that you can equate a knockout mouse to a human being.  Even if you put human-being cells in it, it really becomes nothing more than a really fancy tissue culture prep.  So, yes; it is an incredible model and I would love to use it in some research that I do, too, but I don't know that that--that alone is not going to give us an answer.

          DR. ALTER:  It does give you an answer.  It is not the same as humans, but your question is are there infectious virions in these units.  And it will answer that question.  You can say whether these livers become infected and that is all you can say, is that they become infected.  You can't say anything about the clinical course, the severity or whether the same would happen in humans.  You just say there are infectious particles in that material.

          DR. HOLLINGER:  I guess I would have to take an exception to that because, again, in a human model, even with all the other things, you can get uptake of virus.  You can get eclipsing but you may not have any replication at all for a variety of reasons.  And you don't know that that is going to happen in these chimeric mice.

          Certainly, you could say in the chimeric mouse model, it did, but I am not sure you can make that conclusion outside the human model.  And I take, for example, one example would be Prince's study in which he did use a chimpanzee model.  Chimpanzees are, what, 99.99 percent similar to humans.  And, in that model, he gave 260 to 2,098, I believe it was, genomic equivalents to three chimpanzees none of which developed Hepatitis B.

          So I do think there may be some differences.  So you take that, and then you take your chimeric mouse model and you say, which one is right.  Maybe Prince didn't do all the things that should have been done or maybe there were some differences in that material. 

          But I am not sure we are able to take this mouse model, this chimeric mouse model in which you have taken some human tissue, you have altered it in a variety of ways to make it replicate or grow in these animals.

          DR. Di BISCEGLIE:  But, Blaine, don't you think that if you can demonstrate replication in the mouse, the positive means something.  A negative experiment doesn't necessarily mean anything; right?

          DR. HOLLINGER:  No, because I don't think necessarily that you might have full replication in a human model for whatever reasons, molecularly or otherwise.  As I said, there are a variety of steps in which this virus gets into a cell and is processed and is eliminated from the cell.  It may not be eliminated from a--

          DR. Di BISCEGLIE:  Yes.  Again, that is a negative experiment.  A positive experiment would be fine.

          DR. HOLLINGER:  Positive in the chimeric mouse model but I am not sure it is equivalent.

          DR. ALTER:  It is not equivalent and a chimpanzee would be better and a human would be still better if you want to volunteer for that experiment.

          DR. HOLLINGER:  You have already sent me to Bolivia.  [Laughter.]  That is an inside joke.

          DR. HOOFNAGLE:  I agree with Harvey on that one.

          DR. ALTER:  But the thing is, Blaine, if you take one of these units, or ten of these units, and you put it into a sufficient number of mice, have positive controls and negative controls, which you can do in mice, and you show that it is--you have infectious particles in there. 

          Maybe you wouldn't do the same in the human, but at least you know there are infectious particles and that makes you pause and consider that it could be risky.  It is not the perfect experiment.  If you do a sufficient number and you don't see any infectious particles, it tells you something, too.  It is not absolute.  But if you have the right control who says, well, we don't find any infectious particles in this model.

          So I think it gives you information.  It is not perfect information.

          DR. HOLLINGER:  No; I agree with that.  But I think I would like to see it at least in a couple of chimps.

          DR. ALTER:  Yes; if you get chimps, it's better.

          DR. HOLLINGER:  To at least document that this model has some equivalence in that regard.

          DR. ALTER:  It is just that they are very hard to come by right now.

          DR. HOLLINGER:  Yes; I understand.

          DR. BIANCO:  I would like to know if Dr. Alter were sitting here in this meeting a year from now and people told him that 50 of these chimeric mice received an injury and they were negative, if you would recommend that the requirement for testing for HBV would be eliminated.

          DR. ALTER:  Assuming that we implemented it and then--the tests were all--yes; I mean, I would.  I would.  I would go back.  I think the FDA has to be flexible and I think if you say we want to get more data and then the data is contrary to your decision, I think you need to go back.

          I think we need to get rid of syphilis testing.  There are a lot of things that are in place that I think we could get rid of.  I think we need to go to pathogen inactivation and then I would take all this away.  So, yes; we can change in the future.  But, right now, we are in the unknown and it is better to go on the safe side, do the experiments and, if they prove to the contrary, then go back.

          DR. HOOFNAGLE:  I have a few comments.  It is an easy experiment to inoculate the mice.  No problem.  There is another issue which I guess Blaine is getting to is that the infection in humans may not be kind of typical Hepatitis B because it is a low-level virus.  You may get a mild infection.  That is going to be very hard to show one way or another because, even if it is--let's say we can find one or two people, it's mild, that doesn't mean anything.

          You have to do 100 people before you can decide--because Hepatitis B is usually mild.  It is only like a third of cases that are even jaundiced.  So it is almost an impossible thing unless you find one good case of an immune-competent person who gets one of these units and gets a good solid case of Hepatitis B.  Otherwise, we will be perplexed.

          I think it is kind of a no-brainer that these are probably infectious.  But what kind of disease they cause in humans and how frequently you see a problem, that is going to be very difficult.

          DR. NELSON:  It is very complicated because the genotype issue, I think, is relevant.  We know that certain genotypes of Hepatitis B have a worse natural history than others.  You might find, if you injected mice with hepatitis genotype A, you know, that they didn't get infected.  But if it was C--or you wouldn't answer the question necessarily.  And it is pretty complicated, I think, to answer this question with a few mice.  It might require quite a few mice.

          DR. BLACKWELDER:   One comment relative to that, if you got a negative result and a sense of no infections and you had 50 mice or even 100 or even more, you could never prove that there is zero probability of infection.  There is always a confidence interval around that zero that allows the possibility of some infection.

          DR. HOOFNAGLE:  You include positive and negative controls in something like that, of course, so the samples that are surface-antigen-positive are causing infection but that is without--the other thing is that the HBV DNA that is detected in serum is not floating around in serum as free HBV DNA.  It is encased in surface antigen.

          So, if we had a more sensitive test for that protein, if protein detection was as good as nucleic-acid detection, then we wouldn't have to bother with this.  We could just improve our test for surface antigen.  So that's another way that this could be reversed if one of the companies came out with a surface-antigen test that was 20 or 100 times more sensitive.

          DR. ALTER:  I don't want to leave the false impression that these mouse studies are easy to do.  They are actually very expensive.  It is a difficult model.  And so you are not going to get 100 mice in the study.  But you might get 10 or 15 or 20.  So it is not perfect and it is not cheap.  We might get somebody who is--some company who is generous to allow this happen without cost is what I am hoping.

          DR. HOLLINGER:  It will be interesting if they use the mouse model, the chimeric mouse model, in the individuals that were--the vaccinated individuals that had HBV DNA in their blood and anti-HBs at certain levels.  The ones that were done, if I am right, were ones from Yoshizawa's study which was acute plasma that did not have any anti-HBs in it.  So it would be interesting to see that later.

          DR. ALTER:  If I could make one more comment.  There are also early HBV culture systems out there.  That is another alternative--or preferably do both.  But I would suggest that, if we can find access to the model, that we then have a committee, subcommittee, to design this experiment so that you don't do it and then go back and say, we should have done something else.  So they are really carefully designed, the specimens are there, but which specimens to use, which controls to use, I think that is needed.

          DR. HOOFNAGLE:  I think we should pursue attempting to show this in humans, too.  And, in this regard, because Hepatitis B is so rare in this country, we have to look like--you know, we get all of our drugs made in India and China.  We will have to do some of our research in China where Hepatitis B is much more common.

          These types of things could be found out if done appropriately and so forth.  I don't think you will be able to show it in the United States.  For one thing, it is a foregone conclusion you are not going to use those units.  But, with a little forward thinking, you might be able--like you showed in Thailand.  There is a much higher rate of this problem in Thailand.

          DR. ZIMRIN:  I hope you weren't suggesting that it would be ethical to transfuse--I mean, if studies designed in this country--

          DR. HOOFNAGLE:  A lookback study.

          DR. ZIMRIN:  Oh; a lookback study.  Okay.  Thank you.

          DR. SIEGAL:  Dr. Alter, again.

          DR. ALTER:  In that study, you would have to prearrange that samples are saved from huge numbers of recipients.  But I agree, the likelihood of something happening there is much higher and you could retrospectively find out who got just DNA-positive, anti-HBs-positive, units.

          DR. NELSON:  I did a study in Thailand that actually showed even a much greater risk than the one that is in press in Transfusion.  It was published in Transfusion about a year ago.  We screened 5,200 surface-antigen-negative donors and found six that were NAT-positive using the Chiron assay.  One was a window period.  The others weren't.

          DR. SIEGAL:  Let's proceed to Question 3; considering the estimated yield or HBV-infected window-period donations and the answers to Question 1, please comment on the benefit of routine screening of blood donors by HBV NAT if testing were performed using available licensed tests on minipools assuming a sensitivity of at least 100 IU/ml for individual samples. 

          Comments?  Questions?  Thoughts?

          DR. Di BISCEGLIE:  Just a clarifying question, perhaps.  Did I understand correctly that the use of minipools and a sensitivity of 100 IUs are sort of conflicting goals.  It is not really--if you dilute them out in minipools, you can't really achieve a sensitivity of 100.  Did I understand that right?   No?  Can somebody maybe help?

          DR. BISWAS:  The issue is if you are using pools of 16, the Ultrio test 16, the limit would be--the sensitivity there is 166 IUs per ml.  If you were using smaller pools, 8 pools of Ultrio in all the other assays that were shown, they would be under the limit of 100 IU/ml.     Is that clear?

          DR. NAKHASI:  May I speak?  A clarification.  It is minipools, and, because we have minipools, as Robin said, with different sensitivities.  So 100, below 100, would be like 8, 6.  Those are the minipools which are below 100 IU.

          DR. CRYER:  I still don't understand the reason for the question.  Who benefits if we answer yes or no.  I don't quite get it.

          DR. BISWAS:  If you vote yes for the 100 IU/ml, then that would rule out the pools of 16 using Ultrio assay.  And Sue Stramer has indicated that she wouldn't like that.

          DR. FINNEGAN:  But, Mr. Chairman, can you separate this into two questions?

          DR. SIEGAL:  Would you like to make a suggestion, Maureen, as to how we do that?

          DR. FINNEGAN:  Yes.  I would like to see us vote on the minipools and then vote on the 100 IU.

          DR. McCOMAS:  But it doesn't look like we are asked to vote.  It looks like we are asked to comment.

          DR. SIEGAL:  Are we asked to vote or comment?

          DR. EPSTEIN:  No; to comment.  And we appreciate that there are two levels of commentary.  One is whether there should be a recommendation and two is what is the appropriate sensitivity level.  And we are looking for discussion here.

          DR. FINNEGAN:  Okay.  Well, I get to be the dumb person here because I am the orthopod and I don't understand any of this.  But it seems to me that the data that was put up said that the 16 minipool is basically equivalent to the others.  So I am not sure why the 100 IU is up there.  I think the minipools is an obvious yes.  I am not sure about the other.

          DR. EPSTEIN:  Okay.  I will give you a moment, Richard, but you have heard two conflicting pieces of data.  You have heard empirical data where eight of nine cases in the Red Cross system were found with minipools of 16 Ultrio.  But you have also seen analytical data showing that there is a projected added benefit with smaller minipools and, in particular, the MPX with a minipool of 6 has a substantially better analytical sensitivity.

          Why FDA converged on a suggestion of 100 IU is because the stand-alone test, the COBAS AmpliScreen, with minipools of 24, has a sensitivity of about 105.  The Ultrio, in pools of 16, was at 166.  If you drop it to pools of 8, it is at 88 which is back in that region of 100.  And the MPX is still better but the question is whether you would set it to the point where there is only one viable test on the market which is not the predominant in use.

          So what we were trying to do was harmonize the available systems.  We were essentially saying, okay, we have got three systems out there.  Maybe, over time, it will only be two.  I don't know.  The point was made earlier by someone that we didn't want necessarily to drive the system toward the multiplex assays.  That may be the evolution but should we be forcing it.

          So, right now, you don't have the use the multiplex assay.  You can use the COBAS AmpliScreen which has sensitivity of 105.  So, it was an attempt to harmonize a standard that recognized the existing systems that could practically be used.

          Now, what you have also heard, though, is that, obviously, if you go from pools of 16 to pools of 8, you have to do twice as many pools.

          DR. FINNEGAN:  But my problem, too, is twofold.  One, not modeling but finite element analysis was used in orthopedics and the relationship between the finite element analysis and reality is huge.  So the modeling is--I have a little skepticism.  But, more importantly, you haven't shown us there is a disease.  So we are talking about toys, but we are not actually talking about a disease.

          So I find it a little difficult to put pressure on the system when we are not sure that we are treating anything.

          DR. EPSTEIN:  Well, yes.  This comes back, I think, to Dr. Alter's point about looking at this in a precautionary way.  If there are infectious units, there will be transmissions.  Now, the estimate that was presented in 2004 at the Secretary's Advisory Committee was 0.16 qualies [ph] per transmission.  We can go into all the details of where did you get that number.

          We know that there is a high rate of transmission from an infectious unit.  You have heard that it could be as few as 10 virions.  You are talking about transfusing whole units so the likelihood of a transmission may be high.  Putting aside the whole question about vaccinees, if we are just talking about the early window period, transmission rates are probably high.

          Disease attack rates probably are low, but there will be disease.  I mean, there are isolated case reports of fatalities from fulminant Hepatitis B.  Partly, we see that in immune-suppressed recipients.  So we can't give you figures.  We can't tell you how many cases of disease.

          I think Blaine put up a chart where he tried to get at that in the Open Public Hearing that Dr. Hollinger showed his estimate for how much disease per annum and over 25 years.  It is small.  But the point here is that we do expect multiplex tests to come into general use and should we be setting and HBV NAT standard or leave that part of test use voluntary.

          That is really what we are getting at.  If they are used, should they meet a standard for HBV because they have a screening claim for HBV, but they are not the same as each other.

          DR. BLACKWELDER:  I still have a question about the 100.  Does the FDA mean for that to be an absolute number?  Or I think you mentioned an assay that had a sensitivity of 105.  If we were in favor of 100, does that mean 105 is ruled out?

          DR. EPSTEIN:  You know, we are here to get comments and we were talking ballpark.

          DR. BLACKWELDER:   Ballpark; okay.

          DR. EPSTEIN:  I think there are three numbers that matter.  The sensitivity of the Abbott PRISM, which is the predominant HBsAg test in use today is about 330 IU.  And then we have the sensitivities of the minipool test which we have repeated several times.  I am happy to say it again.  But they span a range from 22 to 166.  And we were trying to figure out where could we put a standard that would practical.

          The point was also made earlier by Dr. Biswas that FDA was disinclined to propose a standard that would have no obvious benefit over the Abbott PRISM assay.  Exactly, what would be the point?  If we recommended routine use of HBV NAT at a sensitivity no better than antigen detection, it would moot the question. 

          DR. BUSCH:  Jay, if I could, I think there is an apple-oranges issue here.  These numbers that you are referring to with respect to the NAT assays are the 95 percent limits of detection of these assays.  The Abbot PRISM sensitivity of 300 IUs or 1500 copies of the 50 percent limit of detection that, when we do these analyses, we are looking at the--this viral load at the cutoff they asked to see at a 50 percent level.

          And there is about a 1-log difference between the 50 percent and the 95 percent limits.  So the big point is that we will--with the current pool size of 16 with Ultrio, we will achieve a significant window-period reduction and we will pick up a fair number of these window-phase breakthrough infections that we can study.

          So, personally, I think, again, this 100 versus 300 for antigen is not correct.  You would have to multiply the 300 times 5 so it would be more like 1500 IUs for the 95 percent limit of detection. 

          Personally, I think if we move in with pools of 16, we will pick up these cases and can study them.  We will pick up lots of them as we have seen, and we can characterize the dynamics and have the units to look at infectivity.  To force the industry to reduce pool size for this limited incremental value, I think, is not reasonable.

          DR. SIEGAL:  I am going to call a break at this time because, if we don't take a break for lunch now, we are not going to have lunch.  So, I would like this group to reconvene within half an hour if that is possible.  Thank you.

          [Luncheon recess from 1:30 p.m. to 2:00 p.m.]

        A F T E R N O O N   P R O C E E D I N G S

                                               [2:00 p.m.]

          DR. SIEGAL:  Do we want to do some further discussion on Topic 1A before we proceed to Topic 1B?  Would could return to Question 3 if there is anyone with any more comments.

          DR. GLYNN:  So one thing that I wanted to mention is it looks to me like the confidence intervals that were calculated for the theoretical model comparing the 16 minipool to the 8 minipool do appear to overlap.  So, actually, this idea that there is a difference between what the theoretical model says and what the empirical data shows, I am not sure that is true, actually.

          DR. SIEGAL:  It seems to me that we should be addressing this with our biostatistician who is not back yet from lunch.  So maybe we ought to come back to that question.  Anybody else while we are waiting to reassemble?

          DR. ZIMRIN:  I think that is actually the critical point so I would like to address that as well.

          DR. SIEGAL:  Yes; I think that is a very good question, actually.

          DR. COLVIN:  We could almost think of this, though, in terms of a biological question.  What I was thinking about is if we make the assumption, which is not necessarily a good one, that the sensitivity per copy, whether you pool it as 8 or pool it at 16, it is the same.  So the number of copies is the same.  Now, that as an assumption that is not necessarily going to be fair. 

          Then, going from 16 to 8 should cut off, basically, one replication cycle of the virus, meaning approximately almost three days which is about 10 percent of the window period.  So, in some respects, and whether or not--of course, there are going to be confidence intervals around it but the biology would suggest that, by doing this, we are going to cut three more days off the window period.

          DR. SIEGAL:  You could argue that it is intuitively obvious to the most casual observer.  And I also think that the n is so small for all of these events--somebody else should comment on that, but it seems to me that it is very hard to make broad-brush judgments based on whether you pool or 16 or 8.

          DR. COLVIN:  But three days in the window period is not a--that means how many donors in the window period you would be picking up in a year--that is, in terms of yield. 

          DR. COLVIN:  It is approximately 10 percent of the window period; right?  So the window period varies depending on who you are looking at and which study you look at from as low as 20-something days to 50-something days, if I recall the literature correctly.  So it is almost approximately 10 percent of the window period.  Do, if you cut down 10 percent of the window period, you are still 10 percent of the cases.

          DR. SIEGAL:  Okay.  Anybody else?  Dr. Stramer, do you want to comment on that at all, on this last discussion?

          DR. STRAMER:  You mean on the last comment that was made, that I should comment on that?  Well, it is 2.56 and it is a 38-day window period.  Well, yes.  So it is about 7 percent.  But I still go back to what we saw in yield and back to Simone's comment about you have to look at the statistical tests.

          DR. KLEINMAN:  It is 7 percent of the window-period cases but--in the non-vaccinated people and it is no effect in the vaccinated people.  So that one doubling time gets even diluted out if half your yields are in vaccinated donors.  So, I think, the potential benefit of going from 16 to 8 is half of the percentage that you mentioned, so half of, Sue says, three days out of 38 days.  So that is 7 percent, half of that.  So it is really not a lot of benefit even from the theoretical model in going from 16 to 8.

          DR. FORSHEE:  Just to remind the committee, in my earlier presentation we did present our best estimate of the yield that would be achieved using the theoretical model for non-vaccinated.  So, in my presentation, going from the Ultrio 16 to Ultrio 8 would yield about six cases going from that sensitivity.  So that was the estimate that we had.

          The incremental yield for all the tests is available in my presentation if there is ever any question about that.

          DR. KLEINMAN:  So six cases.  But that is 1.7 components per--that is six components.  So, really, it is three or four donor units per year that you are talking about if each one is made into 1.7.

          DR. FORSHEE:  Yes; that is correct.

          DR. SIEGAL:  Any further discussion of Question 3?  Dr. Epstein, did we address this sufficiently well?

          DR. EPSTEIN:  I think we want specific comment on benefit and on an appropriate sensitivity level.  I mean, what the FDA is interested in knowing is are we encouraged to discourage from going forward with a recommendation and to what extent does the committee feel we should be soft or firm about 100 IU. 

          So I am not sure that I have the sense of the committee.  I think we have had a lot of comments about the strength of the data.  But how about--

          DR. CRYER:  I don't think--I, for one, don't know.

          DR. HOOFNAGLE:  I think all the data in favor of it is just modeling.  It is mathematics, that when we hear the data presented with actual samples, it looks like such a cutoff isn't necessary.

          DR. FORSHEE:  But, as I understand with the data in the sample, the data that Sue Stramer presented, we only had one case that was identified using the ID NAT.  So determining what the relative yield would be of different sizes of minipools is just coming from that one donation at this time and so I just think we have limited information there.

          DR. HOOFNAGLE:  There was none that was picked up at the 1 to 8 that wasn't picked up at 1 to 16.

          DR. SIEGAL:  Ann?

          DR. ZIMRIN:  I agree with what several people have said that I don't think that we have seen data that suggests that moving from a minipool size of 16 to 8 is helpful.  There is modeling, a suggestion from the models, but we did not see that confirmed.  I think, in general, the concept of looking at HBV testing with NAT is certainly worth doing, I think, with the window period cases that would be picked up as well as this concerning issue of the breakthrough infections that I think we would all like to have more information.

          So I think the concept is a good one, but I don't feel that we have seen enough information to suggest a change in the specific recommendations in terms of titer-level sensitivity.

          DR. HOLLINGER:  I think that we have seen evidence that you can get the limit of detection at 95 percent down to fairly low levels, less than 5, 6, something of that nature.  So my feeling would be that the limit of detection of an individual minipool sample should be something in the range of 50 or 60 IU/ml as a lower limit.

          You might as well, then, get the most sensitivity that you can out of it.  If you are not going to do individual donation NAT, then one should get the most sensitive detective levels on the minipools that you are going to be testing, whether 6, 8 or 16 or what.

          So, if you are doing 8 and you have a limit of detection of 6, that means you could get down to 50 on the pool or 60 if you want to have a little bit of leeway on that.  So I think that is it.

          I will also just throw out a little novel thoughts to the blood-banking community.  If you really wanted to do these things, what I think would be cheaper for you to do would be, since you have about 82 percent of your donors are repeat donors, that you start vaccinating your donors.  You bring them in.  They donate a unit of blood so you get the unit of blood.  You give them the first dose of vaccine.  Two months later, you have them come back in.  They donate another unit of blood.  You give them another vaccine.  Six months later, you do the same thing.

          You get three or four units that way out of the year, and you have vaccinated your repeat-donor population in doing so.  It is a lot cheaper than doing these tests.

          DR. KLEINMAN:  Something I am not understanding about Recommendation 3 and really the question is directed to Jay.  If the product already--if Ultrio already has a claim for HBV detection at a pool size of 16, and if you were to adopt 100 IU/ml as a requirement and Ultrio in pools of 16 would fail that requirement, is the consequence of putting that in to rescind the current claim that you gave on clinical grounds?

          DR. EPSTEIN:  Well, we would be recommending that it be used at pools of 8.

          DR. KLEINMAN:  Right.  But you have already said it could be used in pools of 16.  That is what is confusing me.

          DR. EPSTEIN:  What we have said in the approval is that it will detect HBV DNA in the absence of HBsAg and anticore.  In other words, there has been proof of principle.  But what we are now talking about is at what sensitivity level do we think there is a sufficient yield to warrant an FDA recommendation for routine use.

          So, yes; it would have the practical effect of the change in the label for donor screening.  Yes.

          I think another perspective on this--I think what has been argued, at least in part, is that the current practice is adequate.  But I think the way the FDA is looking at it, if it is a new standard, we are saying, what would you do completely de novo.  In other words, it was put into place with pools of 16 because it was approved that way but now we are talking about an HBV NAT standard.

          So, if you were doing it de novo, where would you put the limit?

          DR. FINNEGAN:  Jay, how can you justify--what data are you using to choose 100 over 166?  I don't understand that and what is the urgency, or the significance, of going to 100 instead of 166?

          DR. EPSTEIN:  Well, you must understand.  FDA is not wedded to that proposal.  We put that out as a candidate because we saw it as a sensitivity limit that could harmonize continued use of the three available systems.  In other words, we weren't intending to take the COBAS AmpliScreen out of the equation.

          DR. FINNEGAN:  But what is the scientific reason for dropping down 66 IU?

          DR. EPSTEIN:  Okay.  The question in FDA's mind was what is the most sensitive assay that is still practical to be implemented.  It was sort of the same logic that Blaine was putting forward.  Blaine was arguing for 50.  We talked about 50. 

          The way we were looking at it is if we are going to make a recommendation for routine use of HBV NAT, what is the most sensitive test that we could recommend that still is practical--in other words, could be implemented with the available technologies, the things on the market.  And we thought that that was a tolerable limit.

          Why?  Because Ultrio at 8 minipools isn't so different as MPX at 6 in terms of volume of testing and cost of testing.  And, similarly, to Dr. Cryer's point, what would happen if we looked at the AmpliScreen at 24.  It is 105 IU.  Would you have to back off to 20?  But the point is that those are systems that are practical and can be implemented.

          I mean, even though it was done investigationally by the Red Cross, a very large-scale assessment was done with pools of 8.  So it can be done.  So, again, FDA's perspective here, wherever you put the sensitivity limit, it is arbitrary.  But the way we were trying to approach it, trying to balance what is feasible with what is beneficial, was what is the maximum sensitivity that we could set as the standard that is still achievable with the current technologies on the market.  That is the way we were looking at it.

          DR. Di BISCEGLIE:  That sounds reasonable.  But I must say, I think we are fooling ourselves if we think that there is a real difference between 166 and 100 in an analytic test like that.  It is a theoretical construct.

          DR. NELSON:  I can see the reason for having some number because what is to stop somebody from marketing a minipool of 500 or 150, or something like that.  There has to be--I mean, it seems to me maybe 100 is arbitrary.  I agree.  And I would be happy with 166.  But it seems to me that, in addition to having a minipool NAT, there should be some mention of how sensitive it should be.

          DR. SIEGAL:  Dr. Zimrin.

          DR. ZIMRIN:  I could get a lot more excited about a cutoff of 100 if there was any proof that it actually picked up cases.  I think, having a number--if you want to have a number, having a number that is in accordance with the data would be very reasonable which would be, as I see it right now, at 166.

          DR. GLYNN:  I agree with what Ann just said.  So, essentially, we don't have any data that shows that the 16 is any better or worse than the 8.  So I would go with 166 to--actually, it is a little bit more than that.  It is 166.4.

          DR. SIEGAL:  Anyone else wish to comment?  Okay.  Jay, any other--enough?  Okay.

          Let's proceed to Topic 1B, Testing Donors of Human Cells, Tissues and Cellular Tissue-Based Products, HCT/Ps for Hepatitis B Virus Infection by Nucleic Acid Testing.

          The first question; please comment on the potential benefit for HBV NAT testing in the ID NAT format and in the small minipool format for living donors of hematopoietic stem/progenitor cells.  These questions don't call for a vote.  Any commentary? 

          DR. HOLLINGER:  You mean, we only get to use these once? 

          DR. SIEGAL:  It sounds that way. 

          DR. HOLLINGER:  That is kind of fun. 

          DR. SIEGAL:  We could do it anyway, even if we are not asked.  Is there any commentary on this question?

          COMMITTEE MEMBER:  It seems reasonable to use the same standard.

          DR. SIEGAL:  Is that the sense of the committee?  It is.  Since, there is no further commentary, let's proceed to Question No. 2; please comment on the potential benefit of HBV NAT testing in the ID NAT format for other living donors and cadaveric donors. 

          DR. HOLLINGER:  I would just maybe comment about the cadaveric donors.  The blood that is obtained from cadaveric donors is often after a period of time and other things.  I can't see how you could even begin to pool that and do a minipool of cadaveric donors.  There are so many things you can't explain that is in the blood that is happening, proteases, a variety of other things.  To pool it would just be disastrous, in my opinion.  That has to be an individual NAT testing in my opinion.  Living donors are a different story.

          DR. SIEGAL:  Dr. Finnegan.

          DR. FINNEGAN:  I would second that.  I think that the potential for a disease spread to way more people is also an important factor in that, so I would agree with that.

          DR. SIEGAL:  Is there anyone else who wishes to comment or is that the sense of the committee?

          DR. BALLOW:  I would agree as well.  Since the instrumentation coming on line is multiplex, it is going to get done anyway from what I heard this morning.

          DR. SIEGAL:  Anyone else?  Dr. Alter, do you have any comment? 

          DR. ALTER:  No comment.

          DR. SIEGAL:  Okay.  Then I think we have been through the questions.  Dr. Epstein, is that sufficient?  Okay.  Thank you all very much.

          DR. FREAS:  Before we start Topic II, I would like to thank Dr. Alter and Dr. Hoofnagle for participating in Topic I and we appreciate your comments. 

          At this time, I would like to welcome a new temporary member, Dr. James Maguire to the table.  He is Professor of Medicine, Harvard Medical School.  Welcome.

                         Topic II

   Potential Testing Strategies for T. cruzi Infection

                     in Blood Donors

          DR. SIEGAL:  So, Topic II, as you all know, is Potential Testing Strategies for T. cruzi Infection in Blood Donors.  The Introduction will be given by Robert Duncan, Ph.D. of FDA.  

          Dr. Duncan.  We seem to have lost Dr. Duncan.

                       Introduction

          DR. DUNCAN:  Good afternoon. 

          [Slide.]

          I am Dr. Robert Duncan from the FDA.  I am giving you some background and overview of the session on Potential Testing Strategies for Trypanosoma cruzi infection in blood donors.

          [Slide.]

          We have talked about this disease and this agent many times before at the advisory committee.  But I would just, once again, like to give a couple of tidbits about the disease that particularly affect how we make decisions about its implementation.

          Trypanosoma cruzi is a small protozoan parasite that, at one stage, lives freely in the blood.  The disease that it causes is called Chagas disease.  This is often a chronic, asymptomatic infection that is very difficult or impossible to treat with severe symptoms occurring late in the infection in about 30 percent of the cases.  It is primarily found in areas of Mexico, Central America, South America where there are estimated to be 16 to 20 million infected.

          Transmission of the parasite is through the feces of a blood-sucking insect although it can also be transmitted by organ transplant, transfusion.  It can be transmitted orally.  The parasites can be rubbed into other areas like the conjunctiva of the eye or there could be laboratory accidents.

          Blood transfusion transmission has been recognized as a problem in the endemic areas for a long time and, over time, it was estimated that an infected unit has about a 12 to 20 percent probability of transmitting that infection.

          [Slide.]

          After a process of evaluating the need for a test for T. cruzi in this country, one company came to the FDA and we licensed the test in December of 2006, an ELISA test.  Since that time, the majority of blood centers have been testing voluntarily, or at least the majority of blood donations have been tested, for the last two years.

          Under that voluntary testing practice, repeatedly-reactive specimens are mostly retested with an unlicensed radioimmune precipitation assay or RIPA because there is no licensed supplemental test available.

          [Slide.]

          All of the repeatedly-reactive donors are indefinitely deferred and the RIPA-positive donors are counseled and prior donations are traced for quarantine and in order to contact and test the recipients of those prior donations.  An FDA draft guidance recommending universal testing of blood donors and tissue donors was released just about a week ago, March 26, 2009. 

          So, in the context of that draft guidance, the discussion today can be seen as comments to the draft which later will be incorporated into a final guidance.

          [Slide.]

          The current issue for today begins, actually, back in 2007 when the committee noted that a period of universal testing of all donors would generate critical data on the prevalence of T. cruzi infections and that strategies for selective donor testing needed to evaluated and validated.

          Over the past two years, evaluation of the results of T. cruzi testing of donors has led to requests from some blood establishments that the FDA consider recommending selective testing of donors.  All the proposals that have come to us and that we have considered include testing all donors at least once.  Selective testing, the question of how to implement selective testing, revolve around how to evaluate a returning donor who has a prior negative test.

          [Slide.]

          So, in the session this afternoon, we will go over the background, which I am doing now, epidemiology of Chagas disease and T. cruzi infection, a summary of the results of testing of the past two years, evaluation of risk questions as a means of selective testing.  There will be several proposals for approaches to selective testing mentioned.  The FDA will present a risk analysis of the effect on potential new transfusion transmissions of different selective testing strategies and there will be several questions and committee votes at the end.

          [Slide.]

          I'd just like to highlight what we think are the key factors that should be affecting our decision on how to move forward with selective testing, the first being prevalence of T. cruzi infection among blood donors; is the prevalence of the infection rare enough that we can consider reducing the amount of testing. 

          What is the rate of transmission from a presumed seropositive unit?  This will be a critical question as we move forward with less testing.  If there is a very high rate of transmission, that would be a problem.  Another key factor in evaluating selective testing is the ability of risk questions to identify the confirmed positive donors or newly acquired infection, how effective could questions be.

          [Slide.]

          Another key factor is the evidence that has come forward on endemic vector-borne transmission in the United States, what is referred to as autochthonous cases.  It means that we are not just looking at travel to endemic areas.--to some extent, the United States has endemic areas--and an evaluation of how frequent those infections are.

          And then, in general, the frequency of incidence of T. cruzi infections.  Any selective-testing strategy will have to consider the risk of newly acquired infections that may occur after a person is qualified with a prior negative test.

          Finally, I would like to mention the problem of test sensitivity.  We need to look at the prevalence of confirmed positive donors that have had prior negative test results.  And this change from a prior negative to current positive is not because of incident infections but because of low signal-to-cutoff values that exist among a number of the infected individuals that occasionally fall below the cutoff affecting the real test sensitivity in the clinical setting as opposed to the analytical sensitivity.

          [Slide.]

          So there will be a number of presentations that will have data that bear on these key factors.  The American Red Cross survey and follow-up study will be presented by Dr. Susan Stramer where they have asked detailed history questions of repeatedly-reactive donors, where they have complied the results of recipient tracing and testing and quite a few other things that bear on these questions.

          There will also be information that comes from a study by the Blood Systems Research Institute that specifically evaluated risk questions for Chagas infection and their ability to identify the confirmed-positive donors.   We have also had input from a survey of the America's Blood Centers that was given to us by Dr. Celso Bianco.  There won't be a separate presentation on this b ut some of that data appears in various presentations.

          [Slide.]

          I am going to just give a quick overview of a few data points.  A much more detailed presentation will follow.  But, on the question of prevalence, from the study by the American Red Cross combined with the Blood Systems data, up until January of 2009, 19.3 million donations tested.  Among those donations, 2,775 were found repeatedly-reactive on the blood screening test, 677 confirmed-positive by the RIPA.  So, using the RIPA as our confirmed seropositivity, that computes as a prevalence of confirmed-positives of 1 in 28,508.

          From the ABC survey, 9.2 million donations, 1,425 repeatedly-reactive, 436 confirmed-positive for a prevalent of 1 in 21,000.  Overall, it seems to me these are good estimates.  They are actually the best estimates that we have of the prevalence among blood donors.

          But an important thing to keep in mind, this is nationwide.  There are high prevalence areas.  California and Florida from the Red Cross study, 1 in 3,800 in California, 1 in 7,800 in Florida.

          [Slide.]

          One of the ways of evaluating the risk of transfusion transmission from a seropositive unit is the lookback study.  In this case, donors that are confirmed-positive with the RIPA test who have had prior donations, the recipients of those prior donations are followed up and tested.

          In the American Red Cross study, 95 recipients were tested.  One of those 95 was positive and turned out to have been born in El Salvador.  So, based on the potential for a prior infection--I am not including that in this count--so just among the 94 recipients, none of them were consistently positive on various RIPA, ELISA and PCR testing.  So that would estimate a very low rate, near zero, of transfusion transmission by a seropositive, potentially seropositive, unit.

          Among those 94, there were 11, however, that were not positive on the Ortho ELISA but had positivity on one or more of the other tests, the RIPA test, the PCR test.  Some of the cases could easily be discounted as false-positives.  But if we were to take the worst-case scenario, that all 11 of those were actual transmissions, then that would suggest an estimate of transfusion transmission from a potentially seropositive unit of 11.7 percent. 

          That would be a high estimate but, compared to the historical estimate from the endemic areas of South and Central America, that is even below those.  So it is clear that there is a lower rate of transmission from a potentially seropositive unit in the country and there are various reasons why.  But I am just going to continue to move on.

          From the ABC lookback study, there were 147 recipients that were tested.  Two of 147 tested positive by an immunofluorescence assay and further study is continuing on those to verify.  But if we assume that those represent transfusion transmissions, that suggests a rate of 1.36 percent.

          [Slide.]

          So this just gives you an idea of the kind of data that is used to estimate the rate of transfusion transmission.  The risk analysis that the FDA is going to present uses a range of values in this spot and these estimates are within that range--well, they are not within the range.  11 is outside the range.  That study which Richard Forshee will explain much more in detail later used an estimate between 1 percent and 5 percent.

          [Slide.]

          So we might want to look just a little deeper.  If we are really trying to probe this question of transfusion transmission, can we tease apart from those 11 potentially positive donors, are there any with a little bit higher index of concern. 

          One way to assign a slightly higher index of concern would be to look at the donors that donated the blood and had more indication of parasitemia.  So, in that follow-up study, both PCR testing and hemaculture testing were performed on the RIPA-positive donors.

          So, of the donors that were involved in lookback studies, 23 of them were positive by PCR but not by hemaculture.  Six of them were positive by hemaculture but not by PCR and four were positive by both.  Each of these tests would indicate that that donor had a higher index of concern so then the recipient, we might have a higher index of concern.

          From among these 23, three recipients were tested.  Only one of them were among the 11.  It had one single RIPA assay-positive that was not reproducible.  From among the hemaculture-positive donors, nine recipients were tested.  From among those nine, two of them were positive by PRC by not by RIPA.  Dr. Stramer will elaborate a little bit more on these cases.

          And then, from the ones that were hemaculture- and PCR-positive, three follow ups were done and none of them were positive.  So that just gives us a little bit more feel for what is underneath the question of what is the true rate of transfusion transmission from a seropositive unit.

          [Slide.]

          So just some other brief presentations on how to compare different selective testing strategies.  One would be universal testing.  That is the current recommendation.  And the best estimate we could make for that for its effectiveness is the analytical sensitivity of the test.  The Ortho T. cruzi ELISA test system has a 99.88 percent sensitivity.

          From the American Red Cross study, there was an evaluation of questions that were able to distinguish the true positive donors and born in the endemic area was the question with the best record, and you will see more details on that.  But even that was only 75 percent effective at identifying the confirmed-positive donors.

          From the Blood Systems study of a combined risk question, only 64 percent sensitive at identifying the confirmed-positive donors. 

          [Slide.]

          I want to go a little bit into detail about how we have calculated sensitivity of the one-test versus two-test strategy.  This arises from the American Red Cross study in which 17.8 million donors, up through November 30th, were tested.  From within those tests, 394 were confirmed positive.  While evaluating those 394, it was found that 16 of them had been previously tested and tested negative.  So that represents a prior false-positive test.

          We can use that 16 false-positives.  All the prior tests were high negatives, many close to the cutoff.  There was no evidence of newly acquired infections so the presumption is that the prior test was a false-negative.  Therefore, we could take 16 away from 394, or 378.  And, if we were to test only once, then we would miss people at that rate.  378 out of 394 is a 95.94 sensitivity of a test-once strategy based on this dataset.

          [Slide.]

          In a similar way, if we were to use a two-test strategy where each donor is tested first when they come for the first time.  When they come at some other subsequent donation, they are tested again.  If they are negative on both of those tests, then they would be qualified to be tested again indefinitely.  Who would we miss on that?

          From the same study, there were five cases that had been tested at least two times prior, some more than two times, with negative tests.  Likewise, there was no evidence of a newly acquired infection.  These are probably false-negative prior tests.  So, by that analysis, 394 minus 5, or 389, divided by 394 is 98.73.

          [Slide.]

          So that leads to this combined table where you see the sensitivity of universal testing, the range of sensitivities of using risk questions as a screen, the sensitivity of testing one time and then no testing after that or testing two times.  You will see later how these sensitivities are worked up in a risk analysis to the potential for new transfusion transmission based on different testing strategies.

          [Slide.]

          So I thought I would read the questions just once through now to help focus your minds on what we want you to address as you listen to the other presentations this afternoon.

          Question No. 1; does the committee agree with the FDA that scientific data on effectiveness of risk questions in general do not support a selective testing strategy in which donors who previously tested negative for antibodies to T. cruzi are tested again only if their answers to risk questions indicate they have a risk of a newly acquired infection?  So that is the risk strategy question.

          [Slide.]

          Question 2.  We have just put in two parts; do the combined scientific data on risk of transfusion transmission of T. cruzi support a selective testing strategy in which, A, one negative test would qualify a donor for all future donations without future testing or questions regarding risk of a newly acquired infection or, B, if the answer in 2A is no, would negative tests on two independent donations qualify a donor for all future donations without further testing or questions regarding risk of a newly acquired infection?

          [Slide.]

          And then we have a third question asking for comment; please provide any additional comments on considerations for selective testing for antibodies to T. cruzi in repeat donors.

          So, with that, I would like to go to our first speaker in the series, Dr. Susan Montgomery from the Centers for Disease Control in Atlanta who will talk about epidemiology of Chagas disease and T. cruzi in general.

           Chagas Disease in the United States.

          DR. MONTGOMERY:  Thank you. Good afternoon.

          [Slide.]

          I was asked to speak specifically to the risks of acquiring infection in the U.S. and also what we know about the epidemiology of the disease here. 

          [Slide.]

          I just wanted to highlight some points about the life cycle of this parasite.  This is a zoonotic disease.  It is vector-borne, but humans are not necessary to the cycle and there are more than 100 domestic and wild mammal species that have been found to be infected with T. cruzi.  Common hosts include possums, wood rats, raccoons, dogs and cats.  And that is the in peridomestic setting.

          Infection of host and vector is lifelong.  Once a bug picks up the T. cruzi parasite, it is infected for life and can transmit to whoever it feeds and defecates on.  And, similarly, there are enormous reservoirs of non-human infected animals.

          [Slide.]

          This map shows you the areas that are endemic for human Chagas disease in red and then the areas that are, I would say, en-zootic for infected vectors and non-human mammals in gray.  You can see that the range actually extends very far north into North America.

          [Slide.]

          I wanted to briefly touch on the programs for Chagas disease control worldwide.  The programs in Latin America are focusing on controlling transmission, in particular vector control.  However, there is also a strong emphasis on blood safety and the screening of blood donors.           In 2007, the World Health Organization initiated a global network for Chagas disease because of concern of not only in facilitating this control in the endemic countries but also, given the immigration patterns in the last 20, 30 years, non-endemic countries are also dealing with Chagas disease now.  In particular, the situation in the U.S. is unique in that we are what could be considered both endemic and non-endemic for this disease.

          Also, we have had recently the treatment drug donated to WHO which means that there is now a free supply of drug to countries wishing to treat patients.

          [Slide.]

          This diagram is to emphasis the course of Chagas disease in the human host.  Initial infections are mostly asymptomatic.  More than 90 percent of the acute infections pass unnoticed and the acute phase lasts from one to two months, typically.  Then an infected person moves into the chronic phase of this disease and they are asymptomatic, which we are calling the indeterminate form, for years to decades.  So someone is unaware of the acute infection and now is indeterminate, asymptomatic, has no idea they have Chagas disease until if they are within the 20 to 40 percent of patients when then progress to clinical disease, typically heart manifestations.

          The gastrointestinal disease seems to have somewhat of a geographic distribution in that people who acquire their infections in the southern cone are perhaps more likely to have mega-colon or mega-esophagus.  And then a certain proportion of infected people remain asymptomatic for life.

          Although there is some controversy, some researchers feel that, if we were able to follow people into their 70s or 80s or beyond, that we would end up finding some manifestation of Chagas disease.  It is just that most people's lifespans are not that long.

          [Slide.]

          I also wanted to highlight some of the clinical challenges with testing.  There is no gold-standard test for diagnosis.  Serologic tests are varied.  They all have limitations in sensitivity and specificity.  For parasitological diagnosis, and by that I mean identifying the parasite on a blood smear, this requires specific skills and this is especially important in cases of acute infection or reactivation of these, someone who had Chagas is indeterminate and, for whatever reason, has a reactivation of their acute disease.

          There is no test to identify which of the patients who are infected are the ones who are going to go on to develop clinical disease, I would say within their 40s or 50s, typically.  We have no way of telling who that will be and we also have no test to determine cure after treatment with antiparasitic drugs.

          [Slide.]

          So the risk of it in the U.S.  We have more than 300,000 infected immigrants likely living in the U.S.  These are people who acquired their infections when they were back home in their home countries in the endemic areas of Central and South America and Mexico.  But there is also risk of acquiring the infection in the U.S. 

          Certainly people are exposed to infected vector and/or reservoirs and this could be within the U.S., itself, or potentially during travel to other areas; children of infected mothers; transplant recipients, transfusion recipients; and then there have been several cases of laboratory-acquired infections.  I am going to go into each of these categories in a little more detail.

          [Slide.]

          I also wanted to highlight the history of T. cruzi and the vector bugs in the U.S.  I think most people are unaware of this but the vectors have been identified in the U.S. since the mid-1800s.  The discovery of the association between parasite and disease in Brazil by Dr. Chagas was in 1909.  We are now in the centennial.

          However, the parasite was first identified in California just a few years later.  And the first human autochthonous case of vector-born disease here in the U.S. was reported in 1955.  So we actually have a very extensive history with this disease.

          [Slide.]

          This map illustrates the states where T. cruzi vectors have been found.  So the states in yellow, which is essentially the whole southern part of the country, is where one or more of the 11 vector species have been identified.  Texas is the state that has had the largest number of reported species.  They have seven different species in that state.  The other states may have one or more.

          I would argue that some of that is associated with the efforts put into identifying the bugs in those states.  For instance, West Virginia is probably only white because no one has looked in that state.

          [Slide.]

          Now, I have overlaid on the same map, the states where infected reservoir animal species have been found.  And those are shown in green.  So the states that remain yellow are where just the vector species were found but now, in green, are where infected mammals have been reported.

          I have also put red stars on states where human autochthonous cases have been reported from.  We have had more than 18 different animal species identified as infected with T. cruzi.

          [Slide.]

          This is from a recent study that was published looking at the prevalence of infection and vectors in the State of Texas.  And you will see that there are actually wide distribution of the bug and the infection in Texas.  Overall, in this study, all of the bugs tested, 50 percent of them were found to be positive for T. cruzi.  The photograph just illustrates two of the most common species in this part of the U.S.  We often get calls from the public who have identified similar bugs or, in fact, this species of bug in their house or their garden.

          [Slide.]

          These are the published cases of autochthonous transmission in the U.S.  You will note the first one, again, is from 1955.  More recently, cases have been reported from Louisiana and Texas.  Most of the infected people are infants.  However, there are two older individuals who were found to be infected.

          [Slide.]

          I am going to go into a little more detail by describing the age range, again, two weeks to 84 years.  Four of these patients were male.  Four actually presented with acute symptoms of disease.  In one case, it was myocarditis.  In another, it was a pericardial effusion.  But most of them were a nonspecific febrile illness.

          Two cases out of the seven had a primary complaint of bug bites and, in one of those two, there was a fever reported within 48 hours of the bug identification.  In one of the seven, there was an unclear clinical history.

          The vector bugs were found on the property of five cases during the resulting investigations and, on four of the cases' properties, they found infected reservoir animals suggesting that transmission was local.

          [Slide.]

          You are going to hear more about the blood-donor screening having turned up autochthonous cases but I wanted to mention two blood donors in Mississippi that CDC was involved in the investigation of these two cases with State of Mississippi Health Department.  Both were individuals who had never left the U.S. save one who had gone across the border apparently for margaritas but never spent the night.

          On the premises of one of those blood donors, we were actually able to find a triatomine bug stuck in the screen of his home that was positive for T. cruzi.  However, we have no indication that these infections were recent.  Both of them were serologically positive but negative for a circulating parasite.

          I wanted also the highlight that we have initiated a study to try and understand the risk for autochthonous transmission better taking advantage of the blood-donor screening and the identification of numerous--up to now, I think it is about 50 blood donors who are suspect autochthonous cases.  We are performing that in collaboration with Red Cross and Blood Systems.

          [Slide.]

          Because of the question of travel-associated infection, we don't have much data at all, just these two anecdotal cases to describe.  The first is a case that was reported to the Geosentinal system in travel clinics.  It is a 26-year-old Canadian woman who spent six months in the Yucatan in rural Mexico and returned home with a sign--symptom, sign--of acute Chagas disease, Romana's sign, which is a swelling of the orbit.

          The second is a 56-year-old man from California, Northern California, who was identified through blood-donor screening, asymptomatic, normal EKG, no evidence of clinical disease.  His only international exposure was three trips, each less than two weeks, two of those to Mexico and one to a non-endemic area of Argentina.  This man is a hunter.  Those trips were hunting trips and so he was in, I would argue, rural areas of those countries.

          [Slide.]

          Congenital transmission is important to consider.  Although there have been no confirmed cases in the U.S., I think in terms of the questions about country of birth, this may be an issue.  It certainly has been reported from other non-endemic countries such as Switzerland where mothers, immigrant mothers, have delivered infected babies.

          The congenital transmission rate in endemic countries is estimated to be between 1 and 10 percent.  These children are, again, asymptomatic typically, although there can be some non-specific findings at birth, which I have listed there.  Based on our estimate of the prevalence of infection in immigrant population in the U.S., we have calculated between 63 to 315 infected infants may be born per year.  This is using a transmission rate of 1 or 5 percent that has generated the range.

          [Slide.]

          For transfusion transmission, there have been five published cases although CDC has been involved in the investigation of 24 recipients of solid organs from seropositive donors and those organs include heart, liver, kidney and then a combination of pancreas/kidney, liver/kidney or pancreatic islet transplant.  Seven, or 41 percent of 19 recipients that we were able to complete investigations of became infected.

          [Slide.]

          I think this information is probably familiar to you.  These are the same seven transfusion cases that have been reported in the literature, five from the U.S. and two from Canada.  But I would argue that this is largely under-recognized and under-reported.  Again, thinking of the way this disease presents in the acute phase, typically asymptomatic and then, as people move into the indeterminate form, they are, by definition, asymptomatic.

          [Slide.]

          These are the laboratory-associated cases that have been identified in the U.S.   The kinds of exposures that people working in labs get are through handling the infected bugs, handing cultures, either from people or animals.  These are hemacultures.  Needle-stick injuries.  There have been mucus-membrane exposures and potentially inhaling of aerosolized organisms.

          There were eight cases reported in the U.S.  Three were associated with needle sticks.  Three, contact with infectious material in someone who had a break in their skin, and then, for two, the actual exposure is undefined.

          [Slide.]

          We have been saying, for several years now, that we think that most physicians in the U.S. are unfamiliar with Chagas disease and I am happy to say that we now actually have data to support that statement.  Completed a survey of the American College of Obstetricians and Gynecologists, concerned that congenital transmission has not been recognized and maybe one reason for that was that obstetricians/gynecologists were not aware of this disease.  In fact, that is true based on our survey results.

          MedScape recently completed surveys of different specialty--they have websites that are geared for particular specialties in the medical profession and, based on their surveys, the ID physicians are coming out ahead but essentially all specialties are not familiar with this disease.

          Then we also have worked with community-based organizations conducting focus groups trying to reach out to the healthcare provider at the level where an immigrant with this infection might actually receive care at the health-clinic level and, even at that level, the healthcare providers are not familiar with Chagas.

          We have also been involved in a clinical study where patients with cardiac disease, the EKGs that came into a cardiology service are screened for typical EKG changes associated with Chagas.  In subsequent testing of those individuals, 14 percent were positive for Chagas.  And their infections had previously been unrecognized.  So, even the clinical cardiac manifestations of this disease are not recognized in the U.S.

          [Slide.]

          One important limitation to our ability to gather this information and to quantify the risk is that Chagas is not a nationally notifiable disease and is reportable only in one state, Arizona, so far, although Massachusetts is working to make it reportable in that jurisdiction as well.  We have no systematic public-health surveillance.  We are benefitting greatly from the AABB's Chagas Biovigalence System.

          There are competing priorities at the public-health level that often impede our ability to collect this information and there is a lack of public-health testing capacity.  At this point, none of the state public-health labs have testing for Chagas in their facilities and all testing is forwarded to CDC.

          [Slide.]

          I wanted to give you another example of where we think there may be barriers to our ability to understand this disease better in the U.S. and that is consultations at CDC.  The drugs for treatment of Chagas disease are not available outside of CDC in the U.S. because they are not FDA-approved and we have them under investigational new drug IRB-approved protocols.

          At this point of the 765 RIPA-positive blood donors that were reported in 2007, 2008 on the AABB website, we have only heard from physicians treating 115 of those donors.  Of those, we were only able to release treatment drug for 45.  And, granted, some of the patients were not eligible for treatment but, in many cases, the patient would become lost-to-follow-up.  The physician would see them once, call CDC and then the patient never returned.  So, clearly, there are many other barriers at work here.

          [Slide.]

          This graph just demonstrates that there has been definitely a change since the introduction of blood-donor screening.  In the past, starting in 1997, and actually before that but I am only presenting that data from '97 to 2009 here, the releases were largely associated with reactivation in people receiving organ transplants who already had Chagas but it was unknown until they got their transplant and were immunosuppressed and developed an acute parasitemia and illness.

          However, starting in 2007, we have seen an increase in the number of releases and most of them are associated with blood-donor infections.  The increase in clinical patient releases is largely associated with that study I mentioned of cardiac patients with EKG changes compatible with Chagas.

          [Slide.]

          So, to conclude, certainly we have important challenges to address and improving healthcare-provider awareness is right at the top of our list in particular in improving the awareness and, hence, diagnosis of clinical disease, recognizing transfusion transmission which is complicated because typically patients who are receiving transfusions have comorbidities that may make the recognition less than optimum.

          And we are working closely now with the transplant community to improve their awareness and ability to screen transplant recipients and transplant donors for this disease.  We would very much like to quantify the burden of clinical disease in the U.S., not only the cardiac but also gastrointestinal disease burden. 

          [Slide.]

          Then, finally, I wanted to make it very clear that we have no estimates for the risks of transmission in the U.S. because of insufficient data and what we need is studies to investigate the risk of T. cruzi infection by these various modes of transmission, in particular autochthonous but also travel-associated infections, transfusion-associated and the concern with congenital transmission.

          [Slide.]

          I wanted to recognize these three individuals who gave me slides and also contributed to content of the presentation.  Thank you.