Evaluation of HCV RNA by PCR and Signal-to-Cutoff Ratios of HCV Antibody Assays for Diagnosis of HCV Infection

Objective: In this study, we assessed whether a hepatitis C virus (HCV) RNA test could replace recombinant immunoblot assay (RIBA) and reduce unnecessary supplemental tests as the signal-to-cutoff (S/Co) ratio from anti-HCV antibody (Ab) tests. Methods: Anti-HCV Ab tests were performed to screen for HCV infections, and RIBA and real-time polymerase chain reaction were performed for HCV RNA to confirm HCV infection. Receiver operating characteristic curves were evaluated to determine the optimal S/Co ratios for predicting HCV infection. Results: The cutoff value for the S/Co ratio was 3.63 for predicting RIBA results and 10.6 for predicting HCV RNA results. Our data suggested that an S/Co ratio ≥10.6 indicated a high risk of active HCV infection. An S/Co ratio of 3.63 to 10.6 needed further evaluation and repeat HCV RNA testing. No further testing was required for S/Co ratios <3.63 or ≥10.6. Conclusion: We determined that the S/Co ratio of the anti-HCV Ab test provides useful information to confirm HCV infections, including the need for further laboratory testing or clinical follow-up.