Finding the right tests…
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Finding the right tests…
Serology
This test looks for a specific viral protein - the hepatitis B surface antigen - directly in a blood sample, and its presence means hepatitis B virus is currently in your system. It is one part of a larger hepatitis B panel that also checks for antibodies, since the antigen alone cannot separate someone in the first weeks of infection from someone who has carried the virus quietly for years. Known chronic carriers have this test repeated periodically as part of long-term liver monitoring, even when they feel entirely well. A dose of hepatitis B vaccine can occasionally cause a brief false positive for about a month afterward.
The test reports whether hepatitis B surface antigen is present or absent in your blood - a straightforward positive or negative, run alongside antibody markers that give the full picture. Persisting positive for more than six months generally defines a chronic infection rather than one still clearing. Because the antigen shows up before symptoms in many people, this test - rather than symptoms - is often what first flags an infection that would otherwise go unnoticed for years.
Laboratories rarely run this test by itself. It is usually paired with two antibody tests - one for a marker that appears once the virus has been cleared or after vaccination, and one for a marker that shows any past exposure to the virus at all. Reading all three together tells a doctor whether someone is currently infected, has recovered and is immune, or has never been exposed.
Someone whose result stays positive past six months is classified as a chronic carrier. Many chronic carriers have no symptoms for years, which is exactly why ongoing testing matters - repeated blood work and periodic liver imaging catch scarring or early cancer risk long before symptoms would appear on their own.
- A dose of hepatitis B vaccine can make this test transiently positive for about a month afterward - This vaccine-related positive is not a true infection and clears on its own - Mentioning a recent vaccination date to whoever orders your test avoids confusion over the result
A positive result, whether from infection or recent vaccination, is always followed up rather than read alone - repeat testing and the accompanying antibody panel settle which explanation fits.
Yes, a recent dose can cause a brief false positive for about a month. Telling your doctor or the centre about a recent vaccination helps them interpret the result correctly rather than assuming an active infection.
HBsAg detects the virus itself, showing current infection. The accompanying antibody tests instead show whether you've ever been exposed or vaccinated, and whether you've developed immunity - together they give a fuller picture than HBsAg alone.
By definition, a chronic infection means the result has stayed positive for more than six months, and it can remain positive for years or a lifetime without treatment. Regular monitoring is used to track liver health during that time.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
Chronic carriers typically need periodic blood tests and liver imaging to watch for scarring or early signs of liver cancer, even without symptoms. Your doctor sets the monitoring schedule based on your specific results.
There is no fasting requirement for this test. Ask your doctor or the centre when you book if other blood work is planned at the same time.
Yes, the two names refer to the exact same blood test and the exact same viral marker. Labs and requisition forms sometimes use one name or the other, but the result means the same thing either way.