Innovative Hepatitis C Screening: Clinical Utility of the HCV Antigen-Antibody Assay in Japan

The Elecsys ^® HCV Duo (HCV Duo) detects antibodies to HCV (Duo/anti-HCV) and HCV core antigen (Duo/HCV-Ag), offering an efficient, cost-effective, and rapid way to screen for hepatitis C virus (HCV). We evaluated HCV Duo's utility in Japan. We analyzed 373 samples (120 HCV RNA-detectable and 253 HCV RNA-undetectable) from chronic hepatitis C (CHC) patients. Duo/anti-HCV sensitivity was assessed using conventional assays. Duo/HCV-Ag sensitivity and specificity were evaluated based on HCV RNA levels. We categorized 153 untreated CHC patients at Nagoya City University Hospital (NCUH) between 2019 and 2023 by HCV RNA levels. HCV Duo showed 100% sensitivity (373/373) for Duo/anti-HCV and 99.2% specificity (251/253) for Duo/HCV-Ag in resolved infection. Duo/HCV-Ag exhibited 55.0% sensitivity (66/120) in active HCV infections. For HCV RNA levels ≤4.0, 4.1-5.5, and ≥5.6 log IU/mL, Duo/HCV-Ag detection rates were 20.5% (9/44), 33.3% (7/21), and 87.3% (48/55), respectively. At NCUH, 71.2% (109/153) of patients had HCV RNA levels ≥5.6 log IU/mL, while 2.6% (4/153) and 26.1% (40/153) had levels ≤4.0 and 4.1-5.5 log IU/mL, respectively. Duo/HCV-Ag performance improves with higher HCV RNA levels, particularly ≥5.6 log IU/mL. HCV RNA testing is recommended for patients positive for Duo/anti-HCV but negative for Duo/HCV-Ag. Duo/HCV-Ag-positive patients should be referred to hepatologists for further evaluation and treatment.