Hepatitis C Virus Core Antigen (HCVAg): an affordable assay to monitor the efficacy of treatment in DAAs era

Hepatitis C virus (HCV) Core Antigen (HCVAg) and HCV-RNA were tested in 962 plasma/serum samples from 180 patients during Direct Antiviral Agents (DAAs) treatment and at follow-up. One hundred and eighty individuals were included: 71% carried advanced fibrosis and 43% were treatment-experienced. A Sustained Virological Response (SVR) was achieved in 166/180 (92%) individuals: 96/102 (94.1%) naive and 70/78 (89.7%) treatment-experienced (p=0.20). The baseline median levels of HCV-RNA and HCVAg were not significantly different between individuals achieving SVR (5.92 x 10(5) IU/mL, IQR 5.4-6.4, and 3,417 fmol/L, 2,900-3,795) and those without SVR (6.06 x 10(5) IU/mL, 5.63-6.57, and 3,391 fmol/L, 2,828-4,077). The HCV-RNA vs. HCVAg assays results showed a fair correlation with an overall moderate qualitative agreement (kappa=0.52). Among treatment-failed individuals, at failure 100% of the assays results were positive for both techniques, with HCV-RNA median value 3.09 x 10(5) IU/mL (2.10-29.09) and HCVAg median value 1570.28 fmol/L (360.15-9317.67). Undetectable HCV-RNA at EOT showed sensitivity 54%, specificity 100%, negative predictive value (NPV) 93% and positive predictive value (PPV) 100%. Undetectable HCVAg at EOT showed sensitivity 74%, specificity 100%, NPV 97% and PPV 100%. The operative and economic advantages of the HCVAg support the alternative use of HCVAg to monitor DAAs treatment outcome.