Hepatitis C viral RNA in serum of patients with chronic non-A, non-B hepatitis: detection by the polymerase chain reaction using multiple primer sets.

The recently introduced antibody test for hepatitis C virus (HCV) infection has proven to have certain limitations. Since HCV itself is usually present in clinical specimens at very low titers, a useful assay for the virus must have very high sensitivity. We have developed a simple, highly sensitive assay for HCV RNA based on the polymerase chain reaction (PCR). In this test, RNA extracted from HCV infected serum or plasma is used as the template for double PCR with nested primers. Sensitivity studies demonstrate that this assay is able to detect HCV at or beyond the sensitivity level of chimpanzee infectivity. We tested, with several sets of nested primers, 40 patients with chronic non-A, non-B hepatitis (36 seropositive and 4 seronegative) and found that 35/40 were PCR positive including all 4 seronegative patients. Normal human plasma and plasma from hepatitis B infected patients did not react in this test. This assay has proven to be valuable for determining the presence of HCV in various samples; furthermore, it offers the possibility of diagnosis of HCV infection in seronegative patients.