Performance of second- and third-generation RIBAs for confirmation of third-generation HCV EIA-reactive blood donations

BACKGROUND: Licensure of an enhanced HCV screening assay (HGV 3.0 EIA) with out concurrent licensure of a complementary supplemental assay (i.e., RIBA HCV 3.0 strip immunoblot assay [RIBA-3]) decoupled screening and supplement al testing. In March 1998, the FDA Center for Biologics Evaluation and Rese arch (CBER) recommended the use of RIBA-3 on RIBA HCV 2.0 strip immunoblot assay (RIBA-2)-indeterminate units screened with HCV EIA 3.0. STUDY DESIGN AND METHODS: The sensitivity of RIBA-2 and RIBA-3 was compared in tests on HCV 3.0 EIA-repeatably reactive (RR) units identified immediat ely after the implementation of HCV 3.0 EIA screening. Two protocols were e valuated: parallel testing of HCV 3.0 EIA-RR units by RIBA-2 and RIBA-3 and reflex testing of HCV 3.0 EIA-RR and RIBA-3-confirmed-positive units by RI BA-2. All specimens with discordant RIBA-2 and RIBA-3 results and a represe ntative sampling with concordant RIBA results were tested by PCR. RESULTS: In the parallel testing protocol, 99,777 donations were screened, with 245 HCV 3.0 EIA-RR specimens included in the study. Of 166 RIBA-2-posi tive samples, 165 tested positive in RIBA-3 (1 sample reacted to the contro l superoxide dismutase antigen in RIBA-3). Thirty-two (74%) of 43 RIBA-2-in determinate specimens and 4 (11%) of 36 RIBA-2-negative specimens tested po sitive in RIBA-S HCV RNA was identified in 5 (16%) of 32 RIBA-2-indetermina te/ RIBA-3-positive donations, as well as in 26 (70%) of 37 concordant RIBA -2/RIBA-3-positive donations. In the reflex testing protocol, 292,459 donat ions were screened, with 709 HCV 3.0 EIA-RR specimens included in the study . RIBA-3 testing yielded 517 (73%) positive specimens, of which 50 (9.7%) t ested indeterminate and 15 (2.9%) tested negative in RIBA-2. Among the RIBA -discordant specimens, 10 (20%) RIBA-2-indeterminate specimens and 1 (7%) R IBA-2-negative specimens tested positive in PCR; in comparison, 60 (77%) of 78 concordant RIBA-2/RIBA-3-positive units tested positive in PCR. CONCLUSIONS: RIBA-3 is significantly more sensitive than RIBA-2 in testing of HCV 3.0 EIA-screened donations. During the review process of this manusc ript, the FDA licensed the RIBA-3 test.