Hepatitis B Virus (HBV) Prenatal Screen, HBsAg

The Hepatitis B Virus (HBV) Prenatal Screen, HBsAg (hepatitis B surface antigen) is used to identify HBV infection during pregnancy so that infants at risk for perinatal transmission can be recognized and managed. Outside of prenatal care, HBsAg screening is applied to asymptomatic persons in risk groups and to blood donors. In the diagnostic workup of suspected acute or chronic HBV, HBsAg is interpreted with other markers such as antibodies to hepatitis B core antigen (anti-HBc), hepatitis B e antigen (HBeAg), and HBV DNA. The assay supports case finding and population-based or public health screening algorithms.

Hepatitis B is a liver infection caused by HBV that is transmitted through contact with infected blood or body fluids, including transmission from mother to infant around the time of birth. Hepatitis B surface antigen (HBsAg) is the viral surface protein detected by this assay and serves as a direct marker of ongoing infection. HBsAg typically becomes detectable approximately 3–5 weeks after acquisition of HBV, near the end of the incubation period, and remains present throughout the acute phase. Persistence of HBsAg beyond six months is consistent with chronic infection. A nonreactive HBsAg result does not exclude acute hepatitis B if antigen concentrations are below the assay’s detection limit or if antigenic variants are not recognized. Assessment of suspected HBV should not rely on HBsAg alone; additional markers—including anti-HBc and HBV DNA—are used to determine infection stage and infectiousness.