Labcorp has introduced a hepatitis D reflex testing option to its full Hepatitis Testing portfolio, aiming to narrow the gap in hepatitis D virus (HDV) diagnosis. According to the company, fewer than 20% of patients in the United States who are positive for hepatitis B surface antigen (HBsAg) are tested for HDV, despite an estimated 70,000 to 150,000 people living with active infection.
Charles M. Walworth, MD, associate vice president of medical affairs and education at Labcorp, attributes the gap to several factors, including the limited availability of HDV testing in the past and the lack of effective treatment options. In a retrospective analysis, only 8.3% of HBsAg-positive patients were screened for HDV between 2024 and August 2026.
Hepatitis D Reflex Pathway
The new reflex pathway lets clinicians automatically run HDV testing on the original blood sample whenever HBsAg is detected. The company offers three reflex options: a positive HBsAg result on the recommended hepatitis B triple panel, a positive result on a standalone qualitative HBsAg test, and an HDV antibody order for patients with a known hepatitis B diagnosis.
Interpretation of HDV testing results mirrors that of hepatitis C. The HDV antibody assay reports a combined IgG/IgM result as reactive or nonreactive, indicating exposure only. Any detectable HDV RNA signals active infection, which can progress rapidly toward cirrhosis, liver failure, and hepatocellular carcinoma if left undiagnosed.
Lessons from Hepatitis C Reflex Testing
Labcorp’s experience with hepatitis C reflex testing has informed the development of the HDV reflex pathway. A review of over 38 million HCV antibody specimens tested between 2018 and 2024 found that same-day HCV RNA testing on antibody-positive samples rose from 38.0% in 2018 to 82.2% in 2024. This increase in testing has improved detection and treatment of hepatitis C, and similar benefits are expected for HDV.
Walworth reflects on past patients who may have been coinfected with HDV, but for whom testing was unavailable at the time. He notes that earlier detection is critical in superinfection cases, where the disease can progress rapidly. Undiagnosed patients also continue to transmit HBV and HDV through blood, body fluids, and sexual contact.
Guidelines and Barriers to Testing
Guidelines remain a barrier to HDV testing, with the American Association for the Study of Liver Diseases (AASLD) using a risk-based approach, while the European Association for the Study of the Liver recommends universal HDV testing. Walworth reports that none of the three clinical sites he recently canvassed had implemented an HDV testing algorithm, and one was waiting for formal guideline recommendations.
Streamlining HDV testing and reducing the number of visits required for diagnosis are key goals of the reflex pathway. By enabling earlier detection and treatment, the company aims to improve outcomes for patients with HDV infection. The launch of the reflex pathway follows the FDA’s approval of the first U.S. treatment for chronic HDV infection, bulevirtide-gmod (Hepcludex; Gilead Sciences), in May 2026.