Serologic hallmark of HBV infection. First serologic marker to appear (1 " “10 weeks of acute exposure). Patients who subsequently recover; undetectable after 4 " “6 months. Persistent for >6 months in chronic infection.
Normal range: Negative.
Use
Diagnosis of acute, recent, or chronic hepatitis B infection. Determination of chronic hepatitis B carriage.
Limitations
Vaccination for HBV can produce transiently detectable levels of HBsAg in patients ( ≤14 days). Most commonly occurs in hemodialysis patients, neonates, and children.
Some rare mutations result in false-negative test results. In these suspected cases, the presence of virus can be deduced by testing for HBcAb, surface antigen antibodies, and HBV DNA.
Specimens with initially reactive test result but negative (not confirmed) by HBsAg confirmation test are likely to contain cross-reactive antibodies from other infectious or immunologic disorders. Repeat testing is recommended at a later date when clinically indicated.