The Meaning of the U.S. Preventive Services Task Force "I" Recommendation
Ned Calonge, M.D., M.P.H.; Gurvaneet Randhawa, M.D., M.P.H.
The authors of this article are responsible for its contents, including any clinical or treatment recommendations. No statement in this article should be construed as an official position of AHRQ or the U.S. Department of Health and Human Services.
Address correspondence to Ned Calonge, M.D., M.P.H., Chair, U.S. Preventive Services Task Force, c/o Program Director, USPSTF, Agency for Healthcare Research and Quality, 540 Gaither Road, Rockville, MD 20850. E-mail: uspstf@ahrq.gov.
This article first appeared in Ann Intern Med 2004;141:718-19. Select for copyright, source, and reprint information.
The U.S. Preventive Services Task Force (USPSTF) formulates evidence-based recommendations for clinical preventive services. These recommendations are communicated by letter grades that reflect the quality of evidence and the magnitude of net health benefit expected from delivering the preventive service. When the USPSTF finds insufficient evidence to determine the balance of health
benefits or harms of delivering a preventive service, because of a lack of studies, poor-quality studies, or good quality studies with conflicting results, the USPSTF assigns the service an "I" letter grade. The USPSTF found insufficient evidence to recommend for or against screening for hepatitis C virus (HCV) infection in high-risk individuals ("I" letter grade). This recommendation reflects the need for further research that would provide adequate evidence to assess the net health benefit for persons screened for HCV infection.
The U.S. Preventive Services Task Force
(USPSTF) is an independent panel of nationally
renowned, non-Federal experts in primary care and
evidence-based medicine convened and supported
by the Agency for Healthcare Research and Quality
(AHRQ). Congress has charged the USPSTF to
review the scientific evidence for the effectiveness
of clinical preventive services for the purpose of
developing recommendations for the health care
community. While many groups use USPSTF
recommendations, they are primarily aimed at the
primary care clinician who delivers a spectrum of
preventive interventions to apparently healthy
persons seen in the usual practice setting.
In 2004, the USPSTF issued its recommendations
on screening for hepatitis C virus (HCV) infection.1
On the basis of its review of the evidence, the Task
Force recommended against routine screening for
HCV infection in asymptomatic adults who are
not at increased risk (a grade "D" recommendation)
and found insufficient evidence to recommend for
or against routine screening for HCV infection in
high-risk adults (a grade "I" recommendation).
The scientific community appears to agree that the
USPSTF adequately reviewed the scientific evidence
for hepatitis C screening. There also seems to be
agreement that the available screening tests are
accurate and that current antiviral therapy leads to
loss of detectable viremia, although it has not yet
been shown to improve morbidity or mortality.
There appears to be some controversy, however,
about the translation of the evidence into the
USPSTF finding of insufficient evidence to
recommend for or against routine screening for
HCV infection in high-risk adults. Before we discuss this recommendation specifically, it is important to
review what a grade "I" recommendation really means
and how the USPSTF may arrive at this letter grade.
The USPSTF uses an explicit analytic framework
to define the scope of the evidence review for each
topic it considers. The scope includes specifying the
population at risk, the accuracy of screening tests, the
efficacy of interventions (treatments) in improving
health outcomes, and the harms caused by screening
and by the interventions.
Before arriving at a
recommendation, the USPSTF takes into account
the strength of the overall evidence and the balance
between the magnitudes of benefits and harms (or
the net benefit). When there is adequate evidence to
determine the magnitude of net benefit of delivering
a preventive service, the USPSTF assigns 1 of 4
letter grades: A, B, C, or D, which indicate that the
net benefit is substantial, moderate, small, or none,
respectively. (For more information, select to access Task Force Ratings: Strength of Recommendations and Quality of Evidence.)
When there is inadequate evidence
to determine the net benefit, the USPSTF assigns
an "I" letter grade. The "I" letter grade simply
reflects the lack of adequate evidence to make a
recommendation; it is neither a recommendation
for, nor a recommendation against, providing the
service on a routine basis. A preventive service could
receive an "I" letter grade for several reasons:
- Studies may be lacking.
- Existing studies may be of poor quality.
- Good-quality studies may have conflicting results.
Therefore, an "I" recommendation is a call
for additional research that would provide the
appropriate evidence base for the USPSTF to
make either a positive or negative recommendation.
The USPSTF reviewed and evaluated the
evidence base for HCV screening. This review
found no direct evidence—that is, no controlled
trial of the efficacy of screening in improving health
outcomes—to evaluate the benefit of screening for
HCV in either the general or the high-risk
population.1 Therefore, the USPSTF evaluation
focused on the chain of evidence that could be
linked to answer the questions necessary to build
a case for screening.
The USPSTF review identified risk factors
associated with an increased risk for HCV infection
but found no prospective studies to determine the
predictive accuracy of assessing these factors.2 The
USPSTF found good evidence that existing tests—enzyme immunoassay and polymerase chain
reaction—are accurate and have high sensitivity
and specificity. These tests will have higher positive
predictive value when used to screen persons at
increased risk for HCV infection than when used
to screen those at average risk.
To determine the magnitude of benefit of
screening for HCV infection, it is important to
consider the natural history of HCV. Unlike HIV
infection (in which nearly 100 percent of infected persons
will develop AIDS and die as a result), the natural
history of HCV infection is unclear. Only a
minority of persons with chronic HCV infection
(10-20 percent) develop cirrhosis after 20 to 30 years;
there is currently no way to predict who will
develop cirrhosis and who will not. Liver biopsy
is commonly done as a part of diagnostic work-up
and will cause major complications in 1 to 2 percent
of patients. The evidence shows that only 30 to
40 percent of infected individuals referred for treatment
are actually eligible to receive it and that 54 to
60 percent respond with sustained reduced viremia,
although it is not known how long this lasts. In
addition, the evidence shows that 50 to 60 percent of
patients experience adverse effects as a result of
treatment, and these adverse effects lead to many
patients—up to 22 percent of those receiving combination
therapy with pegylated interferon2—withdrawing
from therapy.
It is not known whether current treatment will
prevent severe liver disease such as cirrhosis or reduce
progression to severe liver disease in HCV-infected
persons. It is also not known whether counseling
HCV-positive patients to change behavior decreases
the transmission of infection or improves
intermediate or clinical outcomes. No evidence
shows that counseling against alcohol use slows
the progression to liver disease. There is also no
evidence of the magnitude of harms associated
with screening, such as psychological harms
including anxiety, "labeling," or the impact on
partner relationships.
Because of these gaps in the chain of evidence
needed to demonstrate improved health outcomes
from screening for HCV infection in high-risk persons, the USPSTF gave an "I" recommendation
to HCV screening for this group.
The USPSTF believes that the "I"
recommendation, directed to the primary care
clinician, reflects the lack of adequate evidence
to make either a positive or a negative
recommendation about screening for HCV
infection. There may be other reasons to advocate
for HCV testing—for example, disease surveillance,
research, or disease management in a particular
patient—and these may form the basis for other
expert panels or organizations that may review
the same evidence and arrive at a different
recommendation. This does not change the fact
that there is insufficient evidence to recommend
screening based on proven health benefits for the
individual patient.
Practicing primary care clinicians have limited time
and resources available to deliver preventive services.
The USPSTF believes that services with adequate
evidence of substantial to moderate net health benefit
(those with "A" and "B" recommendations) ought to
receive the highest priority for delivery in the primary
care setting. Once clinicians are able to deliver these
services, they can decide how to prioritize services
that have received "C" and "I" letter grades and, in
rare cases, even those that have received grade "D"
recommendations.
This strategy would be expected to
yield the greatest benefit to the health of individuals
and the population with the most prudent use of
time and resources. This USPSTF recommendation
may not alter the practice of clinicians who already
assess risk factors and screen high-risk patients for
HCV infection. However, it is important to recognize
that high-risk people are screened for HCV infection
in the hope that treatment will lead to improved
health outcomes without causing substantial harms,
not because of a proven, long-term net health benefit.
Finally, a grade "I"
recommendation reflects the need for more research.
Hepatitis C virus infection is an important public
health problem, and better treatment options and
prevention strategies clearly are needed. The "I"
letter grade should be viewed as representing the
USPSTF conclusions based on the evidence
available at this time. The USPSTF continually
updates its recommendations, especially when there
is new evidence of benefit, and looks forward to the
time when its recommendation on screening for
HCV infection can be reconsidered on the basis
of new research.
Replication and iteration are hallmarks of
science. Differences of opinion among independent
experts regarding interpretation of current evidence
are not unusual. An essential theme underlying
all USPSTF recommendations is a commitment
to evaluating the quality of scientific studies
and synthesizing the results in a systematic and
transparent fashion so that clinicians and patients
can make informed decisions.
References
1. U.S. Preventive Services Task Force. Screening for
hepatitis C in adults: recommendation statement.
Ann Intern Med 2004;140(6):462-4.
2. Chou R, Clark EC, Helfand M. Screening for
hepatitis C virus infection: a review of the evidence
for the U.S. Preventive Services Task Force. Ann Intern Med 2004;140(6):465-79.
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Source: Calonge M, Randhawa G. The meaning of the U.S. Preventive
Services Task Force "I" recommendation: screening for hepatitis C virus infection. Ann Intern Med 2004;141:718-9.
AHRQ Publication No. 05-0550
Current as of November 2004
Internet Citation:
Calonge M, Randhawa G. The Meaning of the U.S. Preventive
Services Task Force "I" Recommendation: Screening for Hepatitis C Virus Infection. AHRQ Publication No. 05-0550, November 2004. Originally in Ann Intern Med 2004;141:718-9. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/clinic/3rduspstf/hepcscr/hepcirec.htm