Hepatitis Tests (HBsAg, Anti-HBs, Anti-HCV)
Definition
| Test | What it is | What it shows |
|---|---|---|
| HBsAg | The antigen on the surface of the hepatitis B virus | Active infection (acute or chronic) |
| Anti-HBs | The antibody the immune system produces against HBV, after infection or after vaccination | Immunity (from vaccination or a resolved infection) |
| Anti-HBc | Another antibody produced against HBV, only after infection (vaccination does not produce this antibody) | Past or ongoing infection |
The most commonly confused point: a positive HBsAg means disease, while a positive Anti-HBs means protection. The two have opposite meanings.
Purpose
Detection of current or past hepatitis infections. Reasons for ordering: symptoms such as jaundice, fever or abdominal pain, abnormal liver function tests, known exposure to hepatitis, risk groups (healthcare workers, intravenous drug use, immunosuppression) and routine screening in pregnancy.
Results
- HBsAg positive → active hepatitis B infection
- Anti-HBs positive → immunity due to vaccination or a past, resolved infection
Risks and Limitations
An important limitation for hepatitis C:
The test cannot distinguish an active infection from a past infection that has resolved.
In other words, a positive Anti-HCV does not mean you currently have hepatitis C. An HCV RNA (viral load) test is needed to make the distinction. This must be stated in the glossary so that patients do not panic unnecessarily.