These studies used the polymerase chain reaction (PCR) to identify hepatitis C virus (HCV) RNA in clinical samples collected from patients with chronic liver disease or from blood donors. The relative role of this assay compared with detection of HCV antibodies in serum was evaluated. Weiner and colleagues found that 9 of 15 patients with non-A, non-B (NANB) chronic hepatitis and the only patient with cryptogenic cirrhosis had persistent antibodies to a nonstructural protein of HCV (C100-3). Seven of the 10 antibody-positive patients had HCV RNA detected by a highly sensitive PCR assay; two of the antibody-negative patients also had HCV RNA. The pattern of viral RNA and antibody was evaluated in one patient with acute posttransfusion NANB hepatitis (PTNANB) and in three chimpanzees with acute infection. Viral RNA was detected early after infection and, in each case, before the appearance of antibody. In one chimpanzee, viral RNA disappeared when antibody became detectable. The authors conclude that most patients with chronic NANB liver disease have HCV infection.
Garson and colleagues found that 6 of 1,100 donor blood units were repeatedly positive for antibodies to the C100-3 antigen (anti-C100-3). Only one of these six donor units was found to contain HCV RNA by a “nested PCR” assay. Nested PCR refers to the use of two successive rounds of amplification, with the second round using primers internal to, or nested within, the original two primers. The positive donor unit was the only one of the six antibody-positive units to cause posttransfusion hepatitis in a recipient. Sera from three other confirmed cases of posttransfusion hepatitis were evaluated and in each case one donor unit of blood was found to contain HCV RNA and anti–C100-3. The authors concluded that anti–C100-3 may not be a good predictor of infectivity in blood donors and that direct identification of viral RNA may be required.