The utility of HCV core antigen for evaluation of viremia at 48 weeks posttreatment with direct-acting antivirals

The hepatitis C virus core antigen (HCV-cAg) assay is a cheap and rapid alternative to HCV-RNA detection, while the results were limited to 12 weeks following direct-acting antiviral (DAA) treatment. In this study we aimed to investigate the role of the HCV-cAg assay up to 48 weeks after DAA treatment. We enrolled 98 patients with chronic HCV infection who received DAA treatment in this study. Plasma samples were assessed for HCV-RNA (AmpliPrep/COBAS TaqMan assay, Roche) and HCV-cAg (Abbott ARCHITECT HCV-cAg assay) levels at baseline, 12 weeks (P12) and 48 weeks (P48) after DAA treatment. The sensitivity and specificity of HCV-cAg were compared with those of HCV-RNA. A total of 284 samples from 98 enrolled participants were analyzed. HCV-cAg levels changed in parallel with HCV-RNA levels in HCV-infected patients during and after DAA therapy. HCV-cAg levels showed excellent correlation with HCV viral load (R = 0.951, R² = 0.905, β = 0.951, and P < .001). The overall sensitivity and specificity for HCV-cAg in detecting quantifiable HCV-RNA thresholds were 96.9% and 100%, respectively. Three patients with baseline HCV viremia had nonreactive HCV-cAg (false-negative rate was 1.02%); none of the patients were HCV-cAg positive and HCV-RNA negative. At 48 weeks after DAA treatment, the HCV-cAg assay detected all patients with viremia, demonstrating 100% sensitivity and specificity. In conclusions, the HCV-cAg assay has high sensitivity and specificity for the detection of pre- and post-DAA treatment viremia and may be a useful tool to confirm viremia at P12 and P48.