Hepatitis B tests: HBsAg, anti-HBs and anti-HBc

The three most useful initial tests for understanding your status regarding hepatitis B are HBsAg, anti-HBs and total anti-HBc. Together, they show whether a current infection is present, whether you have been exposed to the virus or whether vaccination has protected you.

A single result can be confusing. A three-test panel is now preferred because the markers can be read together. If infection is detected, additional tests are needed to determine whether it is acute or chronic and whether treatment is indicated.

What does each test mean?

• HBsAg, or hepatitis B surface antigen: a positive result means that the virus is present. If it remains positive for six months or longer, the infection is chronic.
• Anti-HBs, or hepatitis B surface antibody: indicates protection. It may appear after vaccination or after recovery from infection.
• Total anti-HBc, or hepatitis B core antibody: shows that genuine exposure to the virus has occurred. Vaccination does not make this test positive.

This last distinction is crucial. A vaccinated person usually has positive anti-HBs and negative anti-HBc. Someone who recovered from infection usually has both antibodies.

Common result patterns

HBsAg negative, anti-HBc negative, anti-HBs negative: no evidence of previous infection or immunity. Vaccination may be appropriate depending on age and risk factors.

HBsAg negative, anti-HBc negative, anti-HBs positive: immunity from vaccination. Healthy people generally do not need regular antibody level checks.

HBsAg negative, anti-HBc positive, anti-HBs positive: past, resolved infection. The person has natural immunity but should report this history before chemotherapy or immune-suppressing treatment because the virus can reactivate.

HBsAg positive, anti-HBc positive, anti-HBs negative: current infection. Further testing is needed to determine whether it is acute or chronic and how active it is.

HBsAg negative, anti-HBc positive, anti-HBs negative: this is known as isolated anti-HBc. It may represent an old infection with waning surface antibodies, a false positive or, less often, occult infection. Interpretation depends on the clinical context.

How are acute and chronic infection distinguished?

When HBsAg is positive, IgM anti-HBc may be ordered. A positive result, considered with symptoms and other findings, supports recent infection. HBsAg that remains positive for six months defines chronic hepatitis B.

Additional tests for confirmed infection include:

• HBV DNA, or viral load, which measures viral replication.
• HBeAg and anti-HBe, which provide information about the phase of infection.
• ALT and AST, bilirubin and liver function tests.
• Fibrosis assessment using blood scores or elastography.
• Testing for hepatitis D, hepatitis C and HIV.

Who should be tested?

Testing is recommended in several situations, including pregnancy, before chemotherapy or immunosuppression, in people with elevated liver enzymes, household or sexual contacts of someone with hepatitis B, health care workers, people receiving dialysis and those born in or who lived in higher-prevalence regions.

Do not make decisions from one result

The test names look similar, and results may vary depending on the stage of infection. Do not stop medication or assume that you need treatment based on one positive marker. Take the complete panel, your vaccination history and any previous results to your clinician.

See also

• Hepatitis B
• Hepatitis B and pregnancy
• Hepatitis D testing
• ALT and AST liver enzymes