The persistence of hepatitis C virus (HCV) infection remains as a major cause of liver cirrhosis and hepatocellular carcinoma. HCV infection is often asymptomatic, thus diagnosis relies heavily on clinical laboratory assays. As an "indirect" test, the anti-HCV screening assay fails to detect HCV infection in the seroconversion window and might report false-negative results in severely immunosuppressed populations.However, it is cheaper, simpler, and can provide results more rapidly. Therefore it remains the preferred method for screening HCV infection in most clinical laboratories.As a newly developed anti-HCV screening assay, the Elecsys anti-HCV Ⅱ assay has been recently launched. Objective To evaluate Elesys anti-HCV Ⅱ assay performance in Chinese populations and compare it with other widely used anti-HCV screening methods.

Four HCV seroconversion panels, 861 fresh consecutive serum samples under routine clinical conditions, 100 preselected serum samples with low positive anti-HCV results (tested before using the Vitros anti-HCV assay) and 178 samples from patients with HIV infection were tested the Elecsys anti-HCV Ⅱ assay and two comparator assays, Architect anti-HCV and Vitros anti-HCV assay. Confirmatory test was performed using recombinant immunoblot assay (RIBA) 3.0 or HCV RNA tests. Moreover, 203 samples with different HCV genotypes were assessed using the Elecsys anti-HCV Ⅱ assay to test its genotype inclusivity.

The Elecsys anti-HCV Ⅱ assay detected HCV seroconversion 7-14 days earlier than the Architect anti-HCV and Vitros anti-HCV assay. It had 100% sensitivity and superior specificity in screening clinical routine samples. For the routine samples with positive anti-HCV by all the three screening assays, the S/Co values obtained using Elecsys anti-HCV Ⅱ did not correlate with those obtained Architect anti-HCV (P=0.13) Vitros anti-HCV (P=0.22) the S/Co values obtained correlated very well with a Pearson correlation coefficient of 0.97(P<0.01). Totally 73 preselected samples with low positive anti-HCV results remained anti-HCV positive when retested the Vitros anti-HCV assay, among which only 18 samples tested positive using Elecsys anti-HCV Ⅱ and 36 samples tested positive using the Architect anti-HCV assay. The Elecsys anti-HCV Ⅱ assay significantly distinguished the 73 anti-HCV borderline results; 55 negative samples tested using Elecsys anti-HCV Ⅱ had S/Co ratios 0.038-0.13, while 18 positive samples had S/Co ratios 13.58-135.6, respectively.Only one sample with an S/Co ratio of 13.58 by Elecsys anti-HCV Ⅱ was confirmed as RIBA indeterminate, while the other 17 samples with S/Co ≥20.0 were all RIBA positive. There were 161 out of 178 samples from HIV infected patients tested anti-HCV positive while 14 samples tested negative using all the three screening.The remaining three samples generated discordant results among the anti-HCV screening assays. The Elecsys anti-HCV Ⅱ assay, the Architect anti-HCV and the Vitros anti-HCV assay detected 97.6% (122/125) anti-HCV-positive samples from HIV-infected patients with HCV viremia. Using the Elecsys anti-HCV Ⅱ assay, however, the anti-HCV levels in the genotype 3b samples were slightly underestimated.

The Elecsys anti-HCV Ⅱ can further shorten the HCV seroconversion window due to its superior sensitivity. It is sensitive and specific enough for screening HCV infection in clinical routine samples as well.The Elecsys anti-HCV Ⅱ assay can be used together with either the Architect anti-HCV or the Vitros anti-HCV assay to improve the specificity in detecting samples with borderline positive anti-HCV S/Co ratios; this strategy will avoid unnecessary medical visits and psychological harm patients with a borderline positive anti-HCV result. The Elecsys anti-HCV Ⅱ assay is also suitable for testing samples from the immunocompromised patients, due to satisfactory sensitivity. Nevertheless, further investigation of its subtype inclusivity in a larger sample number might be warranted.