HEPATITIS-C VIRUS SEROTYPE-SPECIFIC CORE AND NS4 ANTIBODIES IN INJECTING DRUG-USERS PARTICIPATING IN THE AMSTERDAM COHORT STUDIES

In the present study, the RIBA HCV serotyping SIA was evaluated with a cohort of injecting drug users, Serotyping may be a rapid and cost-ef fective method of determining genotypes in cohort studies. In this stu dy, hepatitis C virus (HCV) antibody-positive sera from a cohort of 33 1 chronically infected injecting drug users, of which 167 were coinfec ted with human immunodeficiency virus (HIV),were serotyped by the RIBA HCV Serotyping SIA. Among the 331 specimens, serotype-specific antibo dies were detected in 250 (sensitivity, 75.5%), in which serotype 1 wa s predominant (57.2%), followed by serotype 3 (26.8%). Among the 331 s pecimens, 164 were HIV negative, and serotype-specific antibodies were detected in 151 (sensitivity, 92.1%), in which serotype 1 was predomi nant (59.6%), followed by serotype 3 (33.8%), For a subset of 58 sampl es taken from 19 chronically infected HCV seroconverters with a mean f ollow-up of 5 Sears, serotypes were compared with genotypes, which wer e determined by a line probe assay (HCV LiPa) and by direct sequencing of the products obtained by nested PCR of the 5' untranslated region. Among the 58 samples with known genotypes, serotype-specific antibodi es were detected in 38 (total sensitivity, 65.5%), with a specificity of 78.9%. Thirty of these serotypeable samples revealed a serotype tha t corresponded to the genotype in the 58 samples (total positive predi ctive value, 51.7%). Of the 58 samples, 23 were coinfected with HIV an d when these were excluded, the total sensitivity increased to 76.5%, with a total specificity of 80.8% and a total positive predictive valu e of 61.8%. The serotyping assay showed a high total sensitivity (96.3 %) for samples positive by HCV RIBA, version 3.0, with four bands, We conclude that the sensitivity of the RIBA HCV serotyping SU is limited by the immunocompetence of the HCV-infected host. In general, samples from HIV-negative individuals containing genotype la had higher sensi tivity, specificity, and concordance in the serotyping assay compared with genotyping, whereas samples containing genotype 3a were found to be more cross-reactive and untypeable, Therefore, the prevalence of ge notypes other than genotype 1 could be underestimated if they are dete rmined by serotyping, and improvements in specificity are recommended.