Comparison of Anti HCV Signal-to-Cutoff Ratio with HCV RNA Results.

Abstract

Anti-HCV antibody level screening is used in the diagnosis of HCV. However, a positive (S/Co > 1) result in the anti-HCV test does not always reflect true positivity. Antibody level results of S/Co ratio > 1 have to be validated through HCV RNA. In this study, we aimed to compare the signal-to-cutoff ratios of patients with positive (> 1) HCV antibody levels with the results of HCV RNA by PCR. In total, 17,021 samples were tested for anti HCV between January 2017 and December 2019. HCV antibody (anti HCV) was performed with a fully automated chemiluminescent microparticle immunoassay (CMIA, Abbot®, Architect System). Real Time PCR test (Anatolia Geneworks HCV, Turkey) was used as nucleic acid amplification method. Of the 17,021 patients, 16,706 (98.15%) tested negative and 315 (1.85%) tested positive in the anti-HCV assay. An additional HCV RNA test was requested for these 315 patients with positive anti-HCV assay results (S/Co ≥ 1) of which 23.81% (75/315) were positive for HCV RNA in serum, with a median (IQR): 5.43 log10 IU/mL (4.75 - 6.01 log10 IU/mL). Patients who tested positive for HCV RNA had significantly higher S/Co values compared to patients who tested negative (median (IQR): 13.38 (12.30 - 14.57) vs. 1.79 (1.34 - 1.79), p < 0.001). When S/Co ratios of patients who tested anti-HCV positive and HCV RNA positive were evaluated, it was assumed that high S/Co values were more relevant to true positivity. It was also concluded that low S/Co ratios needed to be verified through PCR.