Unexplained hepatitis C virus antibody seroconversion in established blood donors.
Understanding of the epidemiology and natural history of hepatitis C virus (HCV) infection is incomplete without reference to the early phase of infection. The prevalence of HCV infection is well documented in numerous reports. The seroconversion pattern in previously antibody-negative blood donors provides a model for the study of the incidence and transmission of HCV infection. Records of HCV antibody tests at the West Midlands Blood Transfusion Centre were reviewed to determine the seroconversion rate in 1994 among previously anti-HCV-negative blood donors. Seroconverting donors were counseled to investigate the possible routes of infection. In 1994, blood donations (n = 256,935) were collected from 149,370 donors; 24 donors (0.016%; 1/6224) were positive in the screening enzyme-linked immunosorbent assay (ELISA) and the third-generation recombinant immunoblot assay (RIBA-3). Two donors previously negative for HCV antibody in ELISA were positive in both tests in 1994. Four donors positive in ELISA and indeterminate in RIBA-3 in 1993 reacted positively in both tests in 1994. One donor negative for HCV antibody on previous screening reacted positively in ELISA and was indeterminate in RIBA-3 in 1994 and has become positive in both tests in 1995. A further 43 donors negative for HCV antibody on previous screening reacted positively in ELISA and were indeterminate in RIBA-3 in 1994. Documented seroconversion can take place in the absence of exposure to recognizable risk factors for the infection. The index donation or the donation immediately preceding seroconversion may be positive for HCV RNA in the polymerase chain reaction.