Background: 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.
Methods: 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.
Results: 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).
Conclusions: 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.