HCV chronic infection diagnosis currently relies on anti-HCV antibody (HCV-Ab) detection. As it cannot differentiate an active infection from a resolved one, its diagnosis must be confirmed by HCV-RNA measurement which is scarcely available in resource-limited settings. Quantifying HCV core antigen (AgC), a marker of viral replication, could shorten this algorithm if used as a one-step tool.
The aim of this study was to assess the performance of the AgC quantification for the diagnostic of chronic HCV in a serum bank of HCV mono- and HCV-HBV or HCV-HIV co-infected patients from Cameroon and the influence of co-infections on the test’s results.
The quantification of the AgC was performed by an automated assay (Abbott Diagnostics) in 465 HCV-Ab negative samples and 544 HCV-Ab and HCV-ARN positive samples (n=1020) collected in patients from the Pasteur Center of Cameroon. Its performance was assessed by calculating its sensitivity and specificity, and building ROC curves in order to compare its results to the gold standard (ELISA and/or PCR) with the Area Under the Curve (AUC).
Among these 1009 sera, 335 were un-infected, 489 were HCV mono-infected, 27 of 78 HIV-infected were co-infected with HCV and 28 of 107 HBV –infected were HCV-HBV. No statistical association was found between the AgC level and our covariates (age, gender, HBV or HIV co-infection). The correlation between AgC and HCV ARN was good in the mono-infected group (r=0.75, p<0.00001) and in the HIV co-infected group (r=0.83, p<0.00001) but lower in the HBV co-infected one (r=0.58, p<0.001). The assay had a sensitivity of 95.7% and a specificity of 99.7% in the mono and un-infected group, corresponding to an AUC of 0.99 (95% CI: 0.98-1.0). In the HBV and HIV-infected groups it has a sensitivity of 96.4% and 100%, a specificity of 96.2% and 88.2%, an AUC of 0.98 (95% CI: 0.95-1.0) and 0.99 (95% CI: 0.97-1.0), respectively. No significant difference between the three AUC was observed (p=0.69). In the mono-infected group the PPV was 98.1%, the NPV 99.3%, LR+=319 and the LR-=0.043. In the HBV and HIV-infected groups we respectively found a PPV of 80.2% and 57.6%, a NPV of 99.4% and 100%.
AgC quantification displayed high specificity and sensitivity; in addition neither HIV nor HBV coinfection influenced its discrimination capacity. Then it represents a reliable HCV diagnosis tool and, being less costly than viral load tests, could ease HCV screening, notably in resource-limited settings.