FDA
TALK PAPER

Food and Drug Administration
U.S. Department of Health and Human Services
Public Health Service 5600 Fishers Lane Rockville, MD 20857
FDA Talk Papers are prepared by the Press Office to guide FDA personnel in responding with consistency and accuracy to questions from the public on subjects of current interest. Talk Papers are subject to change as more information becomes available. 
 
T99-9                          Print Media:         301-827-6242 
February 12, 1999              
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FDA LICENSES IMPROVED SUPPLEMENTAL
TEST FOR HEPATITIS C

FDA approved an improved, more specific, supplemental test to confirm screening test results for antibodies to the hepatitis C virus (HCV). The new supplemental test, called the RIBA HCV 3.0 Strip Immunoblot Assay (SIA), is used to test blood specimens that have already tested repeatedly reactive on licensed screening tests. This new test can detect one more type of antibody to the HCV virus than the previous supplemental test and is better at distinguishing truly positive from falsely positive test results.

The practical and public health significance of this new supplemental test is heightened because of a recent Department of Health and Human Services recommendation to blood banks and medical facilities to notify patients who received blood from donors who subsequently were found to be possibly infected by HCV. Notifications of blood recipients consistent with this recommendation are scheduled to begin no later than March 1999. The new RIBA HCV 3.0 SIA will prevent thousands of unnecessary notifications and subsequent testing and counseling of blood recipients based on inconclusive (indeterminate) HCV test results.

HCV is a major cause of serious illness and mortality in the U.S., with four million Americans estimated to be infected. However, only seven percent of cases were acquired from blood transfusions, and most of these infections occurred before 1990 when blood donor screening for hepatitis C became possible.

Improved screening tests were put into use in July 1992. Occasionally, however, these very sensitive blood screens that rarely miss a true infection can give a false positive result -- a test result that may not reflect a true infection.

Currently, the risk of contracting HCV from a unit of blood is extremely low -- approximately 1 in 100,000 units transfused.

The RIBA 3.0 Strip SIA is a three-stage test which uses five genetically engineered HCV antigens -- proteins that react to HCV antibodies. The previous version of the test used four antigens. These antigens are coated as individual bands on test strip. If antibodies to HCV are present in a blood specimen, the antibodies will bind to the corresponding antigen band on the strip and can be seen after a chemical reaction.

The new test was evaluated in multi-center trials of several population groups. In one study using a population of healthy blood donors, about 30% of repeatedly reactive test results were interpreted as indeterminate by the previous test. Only about 7 percent of these same results were interpreted as indeterminate by the RIBA 3.0.

The RIBA 3.0 Strip SIA is manufactured by Chiron Corporation, Emeryville, Calif., and will be distributed by Ortho Diagnostic Systems, Inc., in Raritan, N.J. The previous version, the RIBA HCV 2.0 SIA, was approved in June 1993 and was also manufactured by Chiron.

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