Abstract: Objective Contradictory results in testing anti-hepatitis C virus antibody by chemiluminescence immunoassays (CLIAS) are very common, especially in the cases of low-level anti-HCV. The aim of this study was to explore the diagnostic values of various methods of single detection for low-level anti-HCV and to analyze their effectiveness.Methods A total of 84 serum samples were assessed for HCV via chemiluminescence microparticle immunoassay(CMIA), Enzyme-linked immunosorbent assay (ELISA), electro chemiluminescence immunoassay (ECLIA), recombinant immunoblot assay (RIBA) and Polymerase Chain Reaction (PCR) assay.Results Of the 31 samples with an anti-HCV S/CO ratio between 0.40-10.0 as tested by Architect, 45.16% were indeterminate, 25.81% were positive, and 29.03% were negative according to RIBA. Furthermore, 2 out of 19 samples were related with RF, IgG or IgA. Areas under the ROC in ECLIA, CMIA, HCV-Ag and HCV-RNA were 1.000, 0.997, 0.753 and 0.679, respectively, and their cut-offs were 15.85 COI, 3.31 S/CO, 3.32 fmol/l and 3.94E+03 copies/ml, respectively. The HCV Ag test showed a strong correlation between the logarithmic values of HCV-RNA and HCV-Ag (R=0.91, P<0.001). Of the positive RIBA samples, 97.5% presented reactivity for Core or NS3 antigens on nitrocellulose immunoblot test strips, while only 37.5% presented reactivity for NS4-1 or NS5 antigens and only 2.5% for NS4-2.Conclusion Two methods are required for testing Low-level anti-HCV to improve the diagnostic accuracy, and reference values of 15.85 COI (ECLIA) and 3.31 S/CO (CMIA) are recommended. To some extent, HCV-Ag may be assayed instead of HCV RNA.

Key words: CMIA, ECLIA, anti-HCV, HCV-Ag, RIBA