Evaluation of a third-generation screening assay for anti-hepatitis C virus(anti-HCV) anti-bodies. Comparison of second- and third-generation screening assays and interpretation of discrepant cases.

To evaluate a third-generation (gen.) screening assay (ELISA 3.0) for anti-HCV, we investigated the sensitivity of this commercial kit in comparison with that of a second gen. -assay (PHA 2.0) on 532 sequential specimens. Among the 532 sera tested between January and February 1995, 61 (11.5%) exhibited a reactivity in second- and third-gen. assays, 5 (0.9%) were weakly positive in ELISA 3.0 and negative in PHA 2.0, and only 1 sample (0.2%) was negative in ELISA 3.0 and positive in PHA 2.0. These 6 discrepant specimens were examined for viral peptide antigens by confirming assays (single PHA and RIBA HCV 3.0). Comparing the confirmation patterns on these sera revealed that the enhanced sensitivity of third-gen. assays is mainly due to an increment reactivity of core antigen (c22p) or NS3 (c33c), and not to the addition of NS5 antigen. None of them proved to be HCV RNA-positive by PCR. These results indicate that there are few advantages to screening patients with chronic HCV infection with the third-gen. assay as compared with the second-gen. assay.