Evaluating the utility of a two‐assay serological algorithm for hepatitis C screening in a low prevalence population

INTRODUCTION: Screening for hepatitis C virus (HCV) is performed by testing for anti‐HCV antibodies, which may yield false‐positive results leading to additional testing and other downstream consequences for the patient. We report our experience in a low prevalence population (<0.05%) using a two‐assay algorithm aimed at testing specimens with borderline or weak positive anti‐HCV reactivity in the screening assay by a second anti‐HCV assay prior to confirming positive anti‐HCV results with RT‐PCR. MATERIALS AND METHODS: Retrospective analysis of 58,908 plasma samples was obtained over a 5‐year period. Samples were initially tested using the Elecsys Anti‐HCV II assay (Roche Diagnostics), with borderline or weakly positive results (defined in our algorithm as a Roche cutoff index of 0.9–19.99) reflexively analyzed using the Architect Anti‐HCV assay (Abbott Diagnostics). The Abbott anti‐HCV results dictated the final anti‐HCV interpretation for reflexed samples. RESULTS: Our testing algorithm resulted in 180 samples requiring second‐line testing, with final anti‐HCV results interpreted as 9% positive, 87% negative, and 4% indeterminate. The positive predictive value (PPV) of a weakly positive Roche result was 12%, which was significantly lower than the PPV using our two‐assay approach (65%). CONCLUSIONS: The incorporation of a two‐assay serological testing algorithm in a low prevalence population provides a cost‐effective method of improving the PPV of HCV screening in specimens with borderline or weakly positive anti‐HCV results.