Hepatitis C virus in blood samples from volunteer donors.

The specificities of four assays for hepatitis C virus (HCV) were compared by using units from volunteer blood donors. Upon Food and Drug Administration licensure of the first immunoassay for anti-HCV, EIA-1, units previously deemed acceptable for transfusion and all subsequent blood donations were screened. EIA-1 repeat-reactive (RR) units were tested for HCV by a second-generation enzyme-linked immunoassay (EIA-2) and by a four-antigen recombinant immunoblot assay (RIBA II) and for HCV RNA by reverse transcriptase polymerase chain reaction. All HCV RNA-positive samples were reactive by both RIBA II and EIA-2. All RIBA II-reactive sera were EIA-2 RR. In EIA-1, 0.45% of the prescreened units and 0.59% of the prospectively screened donors were RR. Of these, 52.5 and 54%, respectively, were EIA-2 RR, 71.4 and 69% of the EIA-2 RR units were reactive on RIBA II, and 93 and 88% of the RIBA II-reactive samples were HCV RNA positive. When the sample/cutoff ratio for EIA-2 was greater than 5, 91% of the samples were RIBA II reactive and 82% of the samples were HCV RNA positive. None of EIA-2 RR units with a sample/cutoff ratio of < 5 was RIBA II reactive or HCV RNA positive. In conclusion, RIBA II and RT PCR results are highly concordant. A sample/cutoff ratio of > 5 in EIA-2 is a good discriminator for the likelihood of a true HCV infection on the basis of RT PCR and RIBA II assays.