Performance of second‐ and third‐generationRIBAs for confirmation of third‐generationHCV EIA‐reactive blood donations

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Abstract
BACKGROUND: Licensure of an enhanced HCV screening assay (HCV 3.0 EIA) without concurrent licensure of a complementary supplemental assay (i.e., RIBA HCV 3.0 strip immunoblot assay [RIBA‐3]) decoupled screening and supplemental testing. In March 1998, the FDA Center for Biologics Evaluation and Research (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 immediately after the implementation of HCV 3.0 EIA screening. Two protocols were evaluated: 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 RIBA‐2. All specimens with discordant RIBA‐2 and RIBA‐3 results and a representative 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‐positive samples, 165 tested positive in RIBA‐3 (1 sample reacted to the control superoxide dismutase antigen in RIBA‐3). Thirty‐two (74%) of 43 RIBA‐2‐indeterminate specimens and 4 (11%) of 36 RIBA‐2‐negative specimens tested positive in RIBA‐3. HCV RNA was identified in 5 (16%) of 32 RIBA‐2‐indeterminate/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 donations 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%) tested indeterminate and 15 (2.9%) tested negative in RIBA‐2. Among the RIBA‐discordant specimens, 10 (20%) RIBA‐2‐indeterminate specimens and 1 (7%) RIBA‐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 manuscript, the FDA licensed the RIBA‐3 test.