The hepatitis B surface antibody test (HBsAb) detects antibodies in the blood to determine if someone is immune to the hepatitis B virus (HBV). A negative or nonreactive result means the individual is not immune.

HBV causes hepatitis B, which is a type of liver infection. The infection may be acute or chronic and can lead to severe complications, such as liver failure. It can also lead to cirrhosis, which is when extensive scarring prevents typical liver function.

An HBsAb test can help identify whether a person is immune to HBV and if they have antibodies that may help fight off future infections. The test can also help determine whether and how recently someone has had exposure to HBV.

This article explains HBsAb test results, how the test works, what to do next, and when to contact a doctor.

A doctor examining nonreactive results of a hepatitis B test. -2Share on Pinterest
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A person may receive a reactive or a nonreactive result from an HBsAb test. Doctors can interpret these results in different ways, depending on the results of the following two other blood tests:

  • hepatitis B core antibody (HBcAb) test, which can indicate a current or previous infection
  • hepatitis B surface antigen (HBsAg) test, which can indicate a current infection

Reactive HBsAb result

A reactive or positive result means the test has detected surface antibodies in the blood. This typically indicates that a person has previously recovered from the hepatitis B infection and is now immune to HBV.

A reactive HBsAb result also indicates immunity in those vaccinated against hepatitis B.

Nonreactive HBsAb result

A nonreactive result typically means a person is not immune to HBV. Depending on the results of the HBcAb and HBsAg tests, doctors can interpret the nonreactive results in different ways.

If the results of all three tests are negative, a person does not have a hepatitis B infection. A doctor may recommend they take the hepatitis B vaccine, as someone who has never had the virus may be susceptible to it.

If a person receives a nonreactive HBsAb result but reactive results for the HBcAb and HBsAg tests, they may have an acute or chronic hepatitis B infection.

If the results for the HBsAb and HBsAg tests are nonreactive and the HBcAb test result is positive, the results may indicate:

  • a false positive
  • an atypical HBsAg strain that the test laboratory could not detect
  • a previous infection

Doctors use the HBsAb test to detect the presence of antibodies in the blood. The test involves drawing blood for laboratory analysis. HBV has three antigens:

  • surface antigens
  • core antigens
  • e antigens

The immune system responds to the antigens by releasing different types of antibodies specific to the types of antigens. The HBsAb test can detect the presence of surface antibodies, which the immune system produces to counter surface antigens.

A reactive result indicates that a person has had HBV and that their immune system has cleared the virus from their body. It could also suggest that they have received a hepatitis B vaccine. In both cases, the individual will be immune from hepatitis B.

If a person receives a reactive HBsAb result, they are immune to HBV and cannot spread the infection to others.

However, if their HBsAb results are nonreactive, their next steps may depend on the results of further testing.

If someone has received nonreactive results for the HBsAb, HBcAb, and HBsAg tests, they do not have a current HBV infection but are susceptible to the virus. Someone who has never had hepatitis B should schedule a vaccination with their doctor.

If a person’s HBsAb test result is nonreactive, but the results for the HBcAb and HBsAg tests are reactive, a doctor may need to administer further tests.

These results can indicate an acute or chronic infection, which people can transmit through blood, semen, and other bodily fluids.

Preventing transmission

A doctor will advise someone with the virus on treatment and how to avoid transmission to others. Someone with hepatitis B should avoid the following:

  • sex without a condom or another barrier method
  • donating blood, semen, organs, or tissue
  • sharing drug needles
  • sharing their toothbrush, razor, or nail clippers

Anyone who thinks they have been in contact with the hepatitis B virus needs to contact a doctor.

According to the Centers for Disease Control and Prevention (CDC), all adults, infants, and pregnant people need to undergo screening for HBV infection.

The CDC also recommends that healthcare professionals periodically test people with ongoing risk of exposure to HBV and that all adults receive vaccination against HBV.

The hepatitis B surface antibody (HBsAb) test helps determine a person’s level of immunity to hepatitis B. The test looks for surface antibodies, which the body produces in response to certain antigens from the virus.

A nonreactive result can indicate that a person is not immune to hepatitis B, as there are no surface antibodies in their blood.

Depending on the results of other hepatitis B tests, a nonreactive result may indicate that someone does not have hepatitis B but requires vaccination against the virus or has an acute or chronic hepatitis B infection.