Comparative evaluation of supplemental hepatitis C virus antibody test systems zyx C.S. EVANS, L. TOBLER, A. POLITO, zyxwvut J. STEWART, D. CHIEN, J. WILBER, zyxwv S. QUAN, S. DELANEY, G. Kuo, AND M.P. BUSCH Implementation of routine blood donor screening using anti-hepatitis C virus (HCV) enzyme immunoassay (EIA) has resulted in an ur ent need for well-characterized supplemental assays to confirm the presence of 8 C V antibodies. A comparative study of four commercially available supplemental assays is reported here: first- and second-generationversions of a strip recombinant immunoblot assay (RIBA-1 and RIBA-2), an HCV neutralization EIA, and HCV neutralization plus synthetic peptide EIA. Three hundred sixty-seven blood donor specimens that were repeatedly reactive on HCV EIA were studied. Most specimens (93%) were also evaluated by radioim- munoassay (RIA) with a six-antigen panel, and zyxwvu 60 selected specimens were tested for HCV RNA by the polymerase chain reaction (PCR). RIBA-1 and RIBA-2 gave concordant results with 86 percent of specimens, while an additional 13 percent were correctly classified by RIBA-2 but not RIBA-1. Neutralization EIA alone correctly identified 94 percent of the study group, while the remaining 6 percent required the peptide EIA or the combined neutralization-peptideassay system for correct classi- fication. The RIBA-2 and neutraiization-peptideassay systems yielded identical re- sults for 86 percent of specimens, and these results were supported by RIA and selected PCR testing. Only 2 specimens (0.5%) were frankly discrepant, while 51 specimens were indeterminate on either (47) or both (4) assays. When either the RIBA-2 or neutralization-peptide.assay yielded an indeterminate interpretation, the other system correctly classified the specimen (based on concordance with RIA and PCR data) in a high proportion (92%) of cases. The overall high degree of concord- ance between RIBA-2 and neutralization-peptideassays, as well as the correlating RIA and PCR results, supports the validity and utility of these supplementalanti-HCV test systems. TRANSFUSION 1992;32:408-414. Abbreviations: ALT = alanlne amlnotransferease; anti-HBc = antibody to hepatitis B core antigen; antl-HCV = antibody to hepatitis C vlrus; EIA = enzyme Immunoarsay; HCV = hepatltis C virus; iMBC = Irwin Memorial Blood Centers; PCR = polymerase chain reactlon; RIA = radioimmunoassay; RIBA-1 = recombinant lmmunoblot assay, flrst-generatlon; RIBA-2 = RIBA, second-generation. BLOOD COLLECTION FACILITIES in the United States (US) implemented donor screening for antibodies to an antigenic protein (c100-3) of the hepatitis C virus (HCV) immediately following licensure of anti-HCV enzyme immunoassay (EIA) in mid-1990. During the first year of screening, the rate of anti-HCV EIA reactivity in vol- unteer donor populations has ranged from 0.4 to 1.1 percent.'-4 As recommended by the US Food and Drug Administration, the Centers for Disease Control, and the major blood banking organizations, all units that are re- peatedly reactive for anti-HCV are discarded and the donors are deferred pe~manently.~.~ Given the low prev- alence o f the virus in the donor population, a moderate rate of false-positive results was anticipated, and this expectation was validated by the relatively low rates of virus transmission by EIA-reactive donations7-" and of HCV RNA detection with the polymerase chain reaction (PCR).11-13 Consequently, test manufacturers have sought to develop more specific anti-HCV assays, termed sup- plemental tests, to further classify EIA-reactive donors so that appropriate notification and counseling zyx can proceed. Although no supplemental tests have been licensed by the US Food and Drug Administration to date, several supplemental anti-HCf assay systems have been devel- oped for commercial use and are being increasingly ap- plied in both research and clinical ~ ettings.~-'~~~~-~~ These From Irwin Memorial Blood Centers and the University of California at San Francisco, San Francisco, California; Chiron Corporation, Emerwille. California: and Abbott Laboratories, Abbott Park. Illinois. - , - Supported in part by National Heart, Lung, and Blood Institute grant Systems are based either on evaluation of serum reactiv- tralization (antibody blocking) techniques. Unfortunately, it is difficult to know how to gauge the performance of Pol-HL-36589 (MPB). Chiron Corporation and Abbott Laboratories provided test kits and performed some assays on coded panels. Received for publication July 29, 1991; revision received October 22, 1991, and accepted October 29, 1991. ity with an expanded panel of HCV antigens or on neu- zy 408