The AMPLICOR HCV Tests for the Detection and Quantitation of Serum or Plasma HCV RNA

Clinical diagnosis of HCV infection is generally accomplished by using immunoserological assays to detect the presence of anti-HCV antibodies. Such immunoserological assays have been approved for blood donor screening, thereby reducing the incidence of post-transfusion hepatitis in the United States. Although useful, immunoserological assays have several limitations. Recent evaluations have shown that interpretation of these immunological tests often is difficult, since 25–90% (depending on the risk group under evaluation) of samples repeatedly reactive in the screening assay are negative on supplemental evaluation with a recombinant immunoblot assay (RIBA) (1 ,2 ). Also, the presence of anti-HCV antibodies indicates prior exposure to HCV infection, but cannot be considered a marker for current infection. Nor can anti-HCV antibody levels be used to monitor response to therapeutic agents. Finally, in cases of acute HCV infection resulting from accidental needlestick exposure, many patients fail to produce antibody to HCV (3 ), which makes diagnosis of HCV infection impossible using immunoserological techniques. At the present time, an immunological assay for direct detection of HCV antigen is unavailable.