Value of HCV antigen-antibody combined HCV assay in hepatitis C diagnosis

Reduction of the window period of hepatitis C virus (HCV) infection represents an important goal in the transfusional and diagnostic settings. Currently, the detection of HCV infection relies on the use of immunoassays to detect viral antibodies. A new enzyme immunoassay (Monolisa HCV Ag-Ab ULTRA) designed to simultaneously detect circulating HCV antigen and anti-HCV antibodies has been developed by Bio-Rad and registered by the European Authorities. Several evaluations have been conducted in Europe to determine whether this new assay can improve early detection of HCV infection. Sensitivity studies included 130 HCV RNA positive/anti-HCV negative samples, 21 well documented seroconversion panels and 430 anti-HCV genotyped samples from France and Italy. Specificity has also been assessed in 15,302 non-selected blood donations and hospital samples. Studies have shown that Monolisa HCV Ag-Ab ULTRA assay has been able to detect 40-90 % of HCV RNA positive/anti-HCV negative samples collected in the window period, improving early detection of HCV when antibodies may be undetectable. The mean delay in detecting HCV infection between HCV-RNA and this new test was found to be 5 days, reducing the window period by an average of 37 days. All samples collected after seroconversion were detected with the HCV Ag-Ab ULTRA assay. The specificity analyzed in 15,302 random blood donations and hospital samples was estimated at 99.86 %. Although less sensitive than NAT (71 % of HCV RNA positive/anti-HCV negative in window period), this assay could be a reasonable alternative when NAT cannot be used for reasons such as cost, organization, emergency or logistic difficulties.