Performance of second- and third-generation RIBAs for confirmation of third-generation HCV EIA-reactive blood donations. Retrovirus Epidemiology Donor Study.
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.


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.
Tobler
L H
LH
Blood Centers of the Pacific-Irwin Center, San Francisco, CA 94118, USA. ltobler@bloodcenters.org
Lee
S R
SR
Stramer
S L
SL
Peterson
J
J
Kochesky
R
R
Watanabe
K
K
Quan
S
S
Polito
A
A
Busch
M P
MP
D001782:Blood Donors; D016174:Hepacivirus / Q000276:immunology*; D006801:Humans; D015151:Immunoblotting / Q000379:methods*; D007124:Immunoenzyme Techniques