PREVALENCE OF HEPATITIS-C VIRUS AND GENOTYPE DISTRIBUTION IN AN AUSTRALIAN VOLUNTEER BLOOD-DONOR POPULATION

BACKGROUND: This study was undertaken to assess the prevalence of hepa titis C virus (HCV) antibody and RNA in first-time blood donors and to examine the HCV genotype distribution. STUDY DESIGN AND METHODS: A th ird-generation enzyme-linked immunosorbent assay (ELISA) was used to s creen 34,725 donors for HCV antibodies. Donors who were repeatably rea ctive were tested in two immunoblot assays-a second-generation and a t hird-generation recombinant immunoblot assay-as well as by a polymeras e chain reaction (PCR) assay. PCR-positive donors were genotyped. All samples were screened for alanine aminotransferase levels. RESULTS: Th e ELISA repeat reactivity rate was 0.55 percent. PCR testing showed th at 69 (38%) of the 183 ELISA-reactive samples contained HCV RNA. The t hird-generation recombinant immunoblot assay identified all 69 viremic samples as antibody positive; however, only 63 tested positive on the second-generation immunoblot. The remaining six PCR-positive donors t ested antibody-indeterminate to the core peptide. Ail six of these don ors had HCV subtype 3a infections. Genotype distribution among 58 samp les showed that 34 were type 1, of which 22 could be further subtyped as 1a (16) and 1b (6); 2 were 2a; 5 were 2b; and 17 were subtyped as 3 a. Donors infected with 2b and 3a had reduced antibody reactivity to t he NS4 and NS3 peptides only on the second-generation immunoblot. CONC LUSION: The prevalence of confirmed anti-HCV and viral RNA in new dono rs is 0.29 and 0.2 percent, respectively. The third-generation recombi nant immunoblot assay was more sensitive than the second-generation im munoblot assay in detecting 2b and 3a HCV subtypes. The inclusion of t he NS5 peptide in the third-generation recombinant immunoblot did not result in positive tests in any additional donors. Rather, the improve ment was due to the increased detection of NS3 and, to a lesser extent , NS4 antibodies. Subtypes 1a and 3a were most prevalent in this popul ation.