Hepatitis B Surface Antigen (HBsAg)

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Subject: Hepatitis B Surface Antigen (HBsAg)

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Definition

  • 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.

 
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