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HBsAb

Hepatitis Biomarker

Sample Needed

Collection Type: Blood

Body System

Related System: Hepatitis

Overview

HBsAb (Hepatitis B surface antibody, also called anti-HBs) is an antibody produced by the immune system against the hepatitis B virus surface antigen (HBsAg). The test measures the presence and quantity of these antibodies in blood to determine whether a person is immune to hepatitis B because of past infection or vaccination. It is used to assess immunity after vaccination, screen people after possible exposure, and evaluate status in pregnancy, healthcare workers, and blood donors. Symptoms prompting testing may include known exposure to HBV, or testing as part of screening programs; many people are asymptomatic. Antibody response can vary with age (older adults often have weaker responses), immune status, and certain medical conditions or medications that suppress immunity.

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Test Preparation

No special preparation is required

Why Do I Need This Test

Which profile is the test included in: Hepatitis panel / Hepatitis screening.
What symptoms may indicate a need for this test: known exposure to HBV, post-vaccination check, pre-employment or prenatal screening, or part of hepatitis evaluation.
What conditions it may diagnose/monitor: establishes immunity (vaccine response or recovery from past infection) and helps guide need for vaccination or boosters.
What could be the reasons for abnormal levels: lack of prior vaccination, vaccine nonresponse, waning immunity, immunosuppression, or recent vaccination/infection.
Biological meaning of abnormal values: low/absent antibody = susceptible to infection; adequate antibody = protective immunity.
What behaviors/lifestyle can cause abnormal values: immunosuppressive therapy, heavy alcohol use, chronic illness, or poor vaccine adherence.
What family history may indicate a need for the test: household contact with a person who has chronic hepatitis B or a family history of HBV infection.

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Understanding Test Results

<10 mIU/mL: indicates no detectable protective antibody the person is susceptible to hepatitis B; vaccination is recommended or a vaccine response check should be repeated after booster.
10–100 mIU/mL: indicates protective immunity (adequate response); usually considered sufficient protection.
>100 mIU/mL: indicates a strong immune response, typically after recent vaccination or full recovery from infection; confers robust protection.
Interpretation must consider other markers: HBsAb positive with HBsAg negative generally means immunity (from vaccine or past infection); HBsAb positive plus anti‑HBc (core antibody) positive suggests natural immunity from past infection.
People who are immunocompromised may not reach protective levels and may need additional vaccine doses or specialist management.

Normal Range

Negative (non-immune): <10 mIU/mL OR Protective (immune): ≥10 mIU/mL

FAQs

Q: What does HBsAb stand for?

A: HBsAb stands for Hepatitis B surface antibody (also called anti‑HBs). It is the antibody produced after hepatitis B vaccination or recovery from infection and indicates immunity. A positive HBsAb result—commonly ≥10 mIU/mL—is considered protective; a negative result suggests susceptibility and may prompt vaccination or booster consideration. It is measured by a blood test.

Q: What is a normal HBsAb level?

A: A protective Hepatitis B surface antibody (HBsAb or anti-HBs) level is generally ≥10 mIU/mL. Levels below 10 mIU/mL indicate lack of immunity and may prompt vaccination or booster. Levels between 10–100 mIU/mL are considered adequate protection; levels >100 mIU/mL indicate robust immunity from vaccination or past infection. Clinical decisions also consider history, timing, and risk factors.

Q: What does positive HBsAg mean?

A: Positive HBsAg (hepatitis B surface antigen) means hepatitis B virus is present in the blood, indicating an active infection. It may represent acute or chronic hepatitis B; persistence beyond six months suggests chronic infection. A positive result implies potential infectiousness and warrants further tests (antibodies, core IgM/IgG, HBV DNA) and clinical evaluation for staging, treatment, and monitoring.

Q: What if HBsAb is high?

A: High HBsAb (anti‑HBs) indicates immunity to hepatitis B—usually from vaccination or past infection. Protective levels are generally ≥10 mIU/mL; higher titres suggest strong protection and no treatment is needed. If HBsAg is negative with anti‑HBc negative, immunity is vaccine‑induced; if anti‑HBc positive, immunity follows past infection. Immunocompromised people or those with exposure concerns should discuss testing or boosters with their clinician.

Q: Can HBsAg and HBsAb both be positive?

A: Yes it’s uncommon but possible. Concurrent HBsAg and HBsAb can occur transiently during early recovery, with mutant HBV strains, after passive antibody administration (HBIG), from recent vaccination during infection, or due to lab interference. It requires clarification with repeat serology, HBV DNA quantification and anti-HBc IgM to distinguish active infection, past exposure, or a false/discordant result.

Q: What is the 5 panel test for hepatitis B?

A: The 5‑panel hepatitis B test measures five markers: HBsAg (surface antigen—current infection), anti‑HBs/HBsAb (surface antibody—immunity or vaccination), anti‑HBc total (core antibody—past or present exposure), anti‑HBc IgM (recent/acute infection), and HBeAg (viral replication/high infectivity). Providers use results together to distinguish acute vs. chronic infection, assess immunity, and guide treatment or vaccination.