[Repositioning HCV immunoblot as a targeted confirmatory tool in screening strategies]

Screening for hepatitis C virus (HCV) infection relies on detecting total anti-HCV antibodies through an enzyme-linked immunosorbent assay (ELISA) performed on a single serum sample. However, in population with low seroprevalence, this one-step approach may lack specificity, leading to false-positive results. A low ELISA ratio combined with negative viremia can raise concerns about either a resolved infection or a non-specific result. The aim of our study was to assess the added value of HCV immunoblot testing in clarifying the serological status of patients without known risk factors for infection when a low ELISA ratio and no detectable viremia is retrieved. We retrospectively reviewed the risk factors of 176 non-viremic individuals with low-positive HCV screening results. An immunoblot was performed on samples from 50 individuals with no documented risk factors for HCV infection. The majority of immunoblot tests (36/50) were negative, while a smaller proportion were indeterminate (8/50) or positive (6/50), including cases with very low ratios close to 1. When used selectively, the HCV immunoblot can resolve ambiguities sometimes generated by the enzyme immunoassay.