2ND-GENERATION HEPATITIS-C VIRUS ASSAYS - PERFORMANCE WHEN TESTING AFRICAN SERA

Sera were collected from 426 volunteers in Uganda at high and low risk for acquisition of hepatitis C virus (HCV). All samples were tested b y the Ortho HCV second generation ELISA (S1) and by the INNOTEST HCV A b second generation enzyme immunoassay, (S2), (Innogenetics, Antwerpen , Belgium). Sera that were repeatedly reactive by either screening ass ay were further tested by each of two different HCV supplemental/confi rmatory assays: a second generation recombinant immunoblot assay (RIBA , Ortho Diagnostics), (Cl), and a line immunoassay (INNO-LIA HCV-Ab, I nnogenetics), (C2). In these populations there were 16 true positives, 351 true negatives, and 59 indeterminate results. Fifty-nine point fo ur percent (253/426) of the samples were repeatedly reactive by the Sl test, while only 2.6% (11/426) were repeatedly reactive by S2. Test S 1 produced a high false positive rate, a low positive predictive value , a specificity of 49.3%, and had a sensitivity of 100%. In contrast, the S2 screening assay had much higher specificity (98.8%), but lacked in sensitivity (31.3%). This poor sensitivity of S2 was based almost exclusively on the fact that the C2 supplemental test classified 9 sam ples as confirmed positive when the homologous screening assay classif ied these samples as negative; several of these were not confirmed whe n using a new generation INNO-LIA. Both the screening tests S1 and S2, and the supplemental assays C1 and C2 exhibited a significant degree of discordance, and neither of the screening tests alone would be adeq uate for use in these populations. (C) 1993 Wiley-Liss, Inc.