Retrospective analysis on the diagnostic performances and signal-to-cut-off ratios of the Elecsys Anti-HCV II assay.

backgroundAnti-HCV assays are widely used as a screening tool for HCV infection. However, diagnostic performances and effective signal-to-cut-off ratios (S/COs) for predicting true HCV infections would vary according to the assays used. Thus, we evaluated the diagnostic performances of the new Elecsys Anti-HCV assay.

methodsA total of 41 694 cases tested by the Elecsys Anti-HCV II assay (Roche Diagnostics, Germany) during January 2013 to December 2015 were retrospectively analyzed by comparing with the diagnosis on HCV infections determined by patients' medical records and results of laboratory tests.

resultsExcluding 62 cases with unclear history of HCV infection, 430 and 41 202 cases were respectively assorted as "true infection" and "no evidence of infection," and 99.85% of the initial results by the Elecsys assay were concordant with the diagnosis on HCV infection. Sensitivity, specificity, positive and negative predictive values were respectively 99.30%, 99.86%, 88.04%, and 99.99%, where the prevalence of the HCV infection was 1.0%. The area under the receiver operating characteristics curve value of the Elecsys assay was 0.9980 (95% confidence interval [CI]=0.9944 to 1.0017). The S/CO by the Elecsys assay for predictive of a true-positive ≥95% of the time was 19.0 (95% CI=15.0 to 25.1).

conclusionThe Elecsys Anti-HCV II assay showed excellent diagnostic performances, particularly in terms of sensitivity, specificity, and NPV. However, the results obtained by this assay with S/CO less than a certain value would need to be retested by HCV RNA PCR or another anti-HCV assay.