Field performance and acceptability of the hepatitis B core-related antigen rapid diagnostic test (HBcrAg-RDT) for detecting high viral load among pregnant women in The Gambia (PROTECT-B)

Background Mother-to-child transmission remains a major source of chronic hepatitis B virus (HBV) infection globally. Identifying pregnant women eligible for antiviral prophylaxis requires HBV DNA testing, which is often inaccessible in resource-limited settings. The hepatitis B core-related antigen rapid diagnostic test (HBcrAg-RDT) may offer a point-of-care alternative, yet prospective evaluation in antenatal care is lacking. We assessed its diagnostic performance, clinical impact, and user acceptability within an HIV/syphilis/HBV triple elimination program. Methods In this multicenter prospective cross-sectional study, treatment-naïve, HBsAg-positive pregnant women were enrolled across four antenatal services in The Gambia. Diagnostic accuracy of the HBcrAg-RDT for detecting high viral load (≥200,000 IU/mL) was evaluated using plasma and capillary whole blood samples, with GeneXpert HBV viral load as the reference standard. Results 5.5% of 343 HBsAg-positive pregnant women had high viral load. The HBcrAg-RDT demonstrated 89.5% (95%CI 66.9-98.7) sensitivity and 98.5% (95%CI 96.4-99.5) specificity with plasma, and 88.2% (95%CI 63.6-98.5) sensitivity and 98.7% (95%CI 96.6-99.6) specificity with capillary blood. At one site implementing universal tenofovir prophylaxis, 77 women started treatment, of whom only four had HBV DNA ≥200,000 IU/mL. An HBcrAg-RDT-guided strategy would have identified all eligible women (4/4) while reducing unnecessary treatment from 100% (73/73) to 4.1% (3/73). Users rated the test highly for ease of use, although incubation time modestly increased workload. Conclusion The HBcrAg-RDT accurately identified pregnant women requiring antiviral prophylaxis and was accepted by users. It represents a feasible, lower-cost alternative to HBV DNA testing and may reduce unnecessary tenofovir use compared with universal prophylaxis strategies.