Is an assay for simultaneous detection of hepatitis C virus core antigen and antibody a valuable alternative to nucleic acid testing?

BACKGROUND: A new enzyme immunoassay based on the simultaneous detection of nucleocapsid proteins of hepatitis C virus (HCV) and anti-HCV (Monolisa HCV antigen-antibody Ultra, Bio-Rad) was evaluated as an alternative to nucleic acid testing (NAT) for the diagnosis of HCV infection during the window period in blood donations. STUDY DESIGN AND METHODS: The study included 107 sequential samples from 10 HCV seroconversion commercial panels; 81 samples were in the preseroconversion phase, and 26 were collected after seroconversion. All samples were tested with HCV antigen-antibody assay and the two minipool (MP) NAT procedures that are routinely used in France (transcription-mediated amplification in pools of 8 and COBAS AmpliScreen HCV test [Roche Diagnostic] in pools of 24 donations). RESULTS: From the 44 samples collected during window period that were MP-NAT-positive, 31 (70.5%) were also positive with the Monolisa HCV antigen-antibody assay. The mean delay in detecting HCV infection between these two methods was 5.1 days (range, 0-24 days). The Monolisa HCV antigen-antibody assay led to a reduction in the window period of 26.8 days (range, 0-72 days). All samples collected after seroconversion were detected with the HCV antigen-antibody assay. The specificity analyzed in 2503 consecutive blood donations was estimated at 99.88 percent. CONCLUSION: This new developed assay presents an improvement for the detection of HCV infection, especially in the early phase of infection when antibodies are undetectable. Although less sensitive than NAT, this assay could be a suitable solution for blood screening in developing countries where NAT (or HCV core antigen-specific assay) is not affordable or its implementation is not feasible.