Hepatitis C test shows promise, pitfalls.

Hepatitis C test shows promise, pitfalls

An experimental blood test that detects antibodies to hepatitis C in donated blood identities many, but not all, tainted units, two studies indicate. The data suggest that the test, now under consideration by the Food and Drug Administration for routine use in blood banks, will reduce the number of transfussion-associated cases of hepatitis C. But the test's inability to flag all infectious units hints at the presence of an undiscovered causative agent underlying some hepatitis cases, and highlights the difficulties of eliminating the potentially fatal river disease.

Viral hepatitis remains the most common complication associated with U.S. blood transfusions. About 90 percent of such cases show no evidence of the viruses responsible for hepatitis A or B; most probably result from hepatitis C virus, first identified in 1988. With no hepatitis C screen yet licensed by the FDA, most U.S. blood banks screen for hepatitis A and B antibodies and for indirect evidence of the C virus, such as elevated levels of a liver enzyme.

Cladd E. Stevens and Patricia E. Taylor of the New York Blood Center and their colleagues tested serum samples saved from 456 individuals who donated blood in 1985 and 1986. They report in the Jan. 5 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION that indirect tests alone would not have identified one-third to one-half of their hepatitis-C-tainted blood units, suggesting the test "should contribute significantly" to reducing the risk of hepatitis C in transfusion recipients.

But a second study reported in the same issue suggests the indirect tests may remain useful even after approval of a hepatitis C screen, James W. Mosley of the University of Southern California School of Medicine in Los Angeles and his colleagues looked at serum saved from 24 transfusion recipients from the 1970s. They found hepatitis C antibodies in only six of 10 recipients who developed non-A, non-B hepatitis. They conclude that the experimental test may be "less than optimal" or that another virus or nonviral agent may cause a significant number of non-A, non-B hepatitis cases.

Researchers remain hampered by their poor understanding of hepatitis C's epidemiology and of how the virus interacts with the immune system. For example, while older donors as a group show a decreased prevalence of hepatitis C antibodies, scientist don't know whether this reflects an age-related loss of antibody, a higher mortality form liver disease in this group, or some other factor. The relationships among elevated liver enzyme levels, persistence of hepatitis C antibodies and actual infectiousness of donated blood also remain unclear.