Interpreting serologic tests for hepatitis C virus infection: balancing cost and clarity.

Although progress has been made toward developing a cheap and accurate method to diagnose hepatitis C virus (HCV) infection, current screening tests have an unacceptably high false-positive rate. Newer tests are more accurate, but also more costly. This paper outlines an approach for interpreting and using these different tests. The second-generation enzyme-linked immunosorbent assay (ELISA) for HCV antibodies, the current screening test for HCV infection, has a sensitivity of approximately 90% but a low specificity. Persons with risk factors for HCV infection, elevated aminotransferase levels, and a positive ELISA result most likely have HCV infection. Confirmatory testing with a recombinant immunoblot assay adds considerably to the cost of diagnosis and should only be used to confirm HCV infection in ELISA-positive patients at low risk or with conditions such as hyperglobulinemia that promote false-positive reactivity. Polymerase chain reaction (PCR) testing is the most sensitive and accurate method of diagnosing HCV infection, but its cost limits its use. PCR testing should be reserved for cases of diagnostic uncertainty, evaluation of possible acute hepatitis C, patients with normal serum aminotransferase levels and anti-HCV antibodies, and patients about to undergo interferon therapy.