Abstract:

Objective To analyze the repeatability and signal-to-cut off (S/CO) ratio of positive predictive value ≥95% in the determination of anti-hepatitis C virus (HCV) antibody by 2 enzyme-linked immunosorbent assay (ELISA) systems.Methods Recombinant immunoblot analysis (RIBA) was used to confirm anti-HCV antibody. Using Addcare ELISA 1100 automatic system (Addcare system) and TECAN+FAME combined system, by indirect ELISA, anti-HCV antibody was determined. High, medium and low concentrations of samples were collected. In 1 run of determination, the determination was repeated for 20 times(holes), and the precision of intra-analysis was calculated. For more than 10 d in a single (hole or pipe), 20 runs of determinations were performed, and inter-analysis precision was calculated .A total of 202 serum samples were collected, and receiver operating characteristic (ROC) curve was used to determine the optimal diagnostic threshold value[signal-to-cut off (S/CO) ratio]of 2 ELISA systems for the determination of anti-HCV antibody. The S/CO ratio scope of positive predictive value ≥95% of anti-HCV antibody determination of 2 ELISA systems was ide.pngied. Results The intra-analysis coefficients of variation (CV) were 5%, 8% and 10% for Addcare system and 3%, 7% and 8% for TECAN + FAME combined system, while the inter-analysis CV were 8%, 12%, 15% and 6%, 10%, 13%, respectively. The optimal diagnostic threshold values (S/CO ratios) of 2 ELISA systems were 3.20 and 2.90. The S/CO ratio scopes of positive predictive value ≥95% of anti-HCV antibody determination of 2 ELISA systems were≥2.41 and≥2.57. Conclusions The Addcare system and TECAN +FAME combined system have excellent repeatability and coincidence rate. The anti-HCV antibody determined by 2 ELISA systems has optimal S/CO ratio, and the S/CO ratio is correlated with confirmation assay positivity, so S/CO ratio can be used to predict anti-HCV antibody positivity. The optimal diagnostic threshold value and the S/CO ratio of positive predictive value≥95% are helpful for improving the results' reliability and reducing the sample numbers of confirmation assay.

Key words: Anti-hepatitis C virus antibody, Enzyme-linked immunosorbent assay, Repeatability, Diagnostic threshold value