The Hepatitis B Surface Antibody (HBsAb) Test

Are you immune to the hepatitis B virus?

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The hepatitis B surface antibody test (HBsAb) detects proteins, called antibodies, that are produced by the immune system in response to the hepatitis B virus (HBV). The test is used to determine if you are immune to the virus after natural exposure or vaccination.

The test should not be confused with either the hepatitis B surface antigen (HBsAg) test or the hepatitis B core antibody (HBcAb) test, both of which are used to determine if you have been infected with HBV.

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This article explains what a hepatitis B surface antibody is, when the test is used, and how the test is performed. It also offers insights into what a positive and negative test result means.

What Is Hepatitis B Surface Antibody?

When you are exposed to HBV, your body mounts an immune defense to specifically target and neutralize the invader. Unlike innate immunity which mounts a generalized defense against all invaders, this type of immunity (called acquired immunity) is disease-specific.

This immune response occurs whether you are exposed to HBV through blood or sexual contact or if you are vaccinated with the hepatitis B vaccine.

The virus has proteins on its surface, called antigens, that serve as its unique identification tag. When HBV enters the body, the immune system will "encode" antibodies specific to these antigens.

There are two types of antibodies, known as immunoglobulins, produced in response to the virus:

  • Immunoglobulin M (IgM) is the antibody that mounts the initial attack but eventually fades away.
  • Immunoglobulin G (IgG) is the antibody that provides long-lasting immune protection against HBV. The immunity can last for many years but gradually wanes over time.

Recap

The hepatitis B surface antibody is specific to the hepatitis B virus. There are two types produced by the immune system: a short-lasting antibody that mounts the initial attack (IgM) and a long-lasting antibody that provides ongoing immunity (IgG).

Purpose of Test

The HBsAb test determines the presence and quantity of HBV antibodies in your blood in order to establish how immune you are to the virus.

The HBsAb test may be used to look for prior exposure to HBV or to check whether your vaccination was successful. It does so by detecting the level of IgG antibodies in the blood.

The test can also monitor your recovery from an acute HBV infection by comparing levels of IgM and IgG. Based on these levels, a doctor can have a rough idea as to how recent the exposure was.

The HBsAb test can also help determine if someone needs a booster vaccine (given that HBV antibodies can drop beneath protective levels over time).

Recap

The HBsAb test detects the presence and measures the quantity of HBV antibodies in the blood. It is used to determine your level of immunity against the virus.

How the Test Is Done

The HBsAb test is done by drawing a blood sample which is sent to the lab for analysis. Your healthcare provider will evaluate the results in line with your vaccination history, symptoms, and exposure risk as well as the results of other hepatitis tests.

Interpreting Results

Your HBsAb test result may either be positive or negative, but the interpretation can vary based on the results of other hepatitis tests. These include the previously mentioned HBsAg and HBcAb tests.

Positive

When the HBsAb result is positive—meaning the surface antibodies are present—it usually means that you have recovered from a recent or prior hepatitis B infection and are immune to the virus. If both the HBsAb and HBcAb are positive, a person is said to be immune due to natural infection.

If you received the hepatitis B vaccine, a positive HBsAb result on its own is also an indication of immunity.

Negative

If your HBsAb test is negative, it can mean many different things, but, in general, it means that you are not immune to the virus.

Even so, there are different ways to interpret the results based on their relationship to the other HBV tests.

Test   Result  Interpretation
HBsAb
HBsAg
HBcAb
Negative
Negative
Negative
Not infected
HBsAb

HBsAg
HBcAb
IgM Positive
IgG Negative
Negative
Negative
Acute (recent) infection
HBsAb
HBsAg
HBcAb
Negative
Positive
Positive
Chronic (ongoing) infection
HBsAb
HBsAg HBcAb
Negative
Negative
Positive
1. Resolved infection
2. False positive
3. Low-level chronic infection

Recap

A positive result is an indication that you are immune to HBV due to natural infection or vaccination. The interpretation of a negative result can vary based on the results of other HBV tests.

Follow-Up

If your HBsAb is positive, it either means you've been infected in the past or received the vaccine and are now immune. You cannot infect others and do not require vaccination.

If all three tests are negative—meaning that you have never been exposed to the virus—you will be advised to get the HBV vaccine.

If your HBsAb test is negative but the other tests are positive, your healthcare provider will need to evaluate you further. Whether your infection is acute or chronic, you still have the ability to infect others and will be counseled on ways to avoid that.

If the results are unclear, all three tests will be repeated.

Recap

If your test results indicate that you are immune to HBV, you cannot infect others and do not need vaccination. If the results show that you've never been exposed to HBV, vaccination would be advised. All other findings require further evaluation.

Summary

The hepatitis B surface antibody (HBsAb) test detects and measures antibodies produced by the immune system in response to the hepatitis B virus. It is one of several tests used to diagnose hepatitis and is used specifically to determine your level of immunity to the virus.

The test involves a simple blood draw that will return either a positive or negative result. A positive result generally means that you are immune to the virus and cannot infect others. A negative result can mean any number of things based on the results of the other tests.

A Word From Verywell

If all of your hepatitis tests are negative, it indicates that you have not been exposed to the virus and are not immune. If this is the case, talk to your healthcare provider about getting vaccinated whether or not you are at risk of hepatitis B.

Even if you are immune to hepatitis B, you may still be at risk for other types of hepatitis, including hepatitis C.

Frequently Asked Questions

  • Can you get over hepatitis B?

    Yes. Most people fully recover from an acute hepatitis B (hep B) infection. For mild symptoms, the best way to get over the infection is with rest, fluids, eating well, and avoiding alcohol, tobacco, and drugs. About 5% of adults with acute hep B will develop chronic hep B, which is not curable but can be managed. 

  • What causes a positive hepatitis B surface antibody test?

    Having immunity against hepatitis B results in a positive hepatitis B surface antibody test. It means you’ve either recovered from the infection or have been successfully vaccinated.

  • When should you be checked to see if you have hep B antibodies?

    A hepatitis B surface antibody test to check for hep B immunity is recommended for:

    • Infants whose mothers may have hepatitis B
    • Professionals likely to be exposed to blood and body fluids
    • People on kidney dialysis
    • Immunocompromised individuals
    • People who have a hepatitis B-positive partner
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6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Song JE, Kim DY. Diagnosis of hepatitis B. Ann Transl Med. 2016;4(18):338. doi:10.21037/atm.2016.09.11

  2. Hepatitis B Foundation. Vaccination.

  3. Centers for Disease Control and Prevention. Interpretation of Hepatitis B Serologic Test Results.

  4. Centers for Disease Control and Prevention. Hepatitis B Questions and Answers for Health Professionals.

  5. Hepatitis B Foundation. Hepatitis B Blood Tests.

  6. Immunization Action Coalition. Hepatitis B.

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