The Threshold Value of Anti-HCV Test in the Diagnosis of HCV Infection
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Abstract
Objective: The initial step in the diagnosis of hepatitis C virus (HCV) infection is to screen for anti-HCV antibody, followed by confirmation of positive results with nucleic acid amplification tests. In the recent studies, using reactivity threshold, S/Co (signal to cut-off) ratio greater than 1 has yielded results that are highly consistent with HCV-RNA test. We aimed to determine the most appropriate S/Co level for anti-HCV enzyme immunoassay (ETA) that would predict HCV infection. Material and Methods: We compared the results of 387 patients acquired by Anti-HCV using microparticle ETA and HCV-RNA using hybridization methods. Taking the HCV-RNA test as gold standard for HCV infection, the sensitivity, specificity and predictive values of ETA test were determined and receiver operating characteristic (ROC) analysis was performed to detect the best threshold of reactivity. Results: ETA test showed 197 (49.2%) positive and 190 (50.9%) negative results, and the sensitivity and specificity were calculated as 94.9% and 60.4%, respectively. Positive and negative predictive values were 38.1% and 97.9%, respectively. ROC analysis revealed that the best S/Co level was 5 and, based on this value, sensitivity and specificity were 92.4% and 76.6%, respectively. Computed positive predictive value was 50.3% and negative predictive values was 97.5%. Conclusion: We investigated the best values of reactivity for anti-HCV ETA test and found S/Co >= 5.