A HBsAg blood test can detect this antigen.
A positive HBsAg result means you have an active hepatitis B virus (HBV) infection and are contagious.
HBV is spread through contact with infected body fluids, such as blood and semen.
Verywell / Brianna Gilmartin
This article discusses the HBsAg test and other tests used to confirm hepatitis B infections.
It also explains how hepatitis B infections are treated and provides prevention tips.
Verywell / Brianna Gilmartin
What Is the HBsAg Test?
HBsAg test is a blood test that detects hepatitis B surface antigen (HBsAg).
HBsAb is a protein on the surface of the hepatitis B virus.
High levels of HBsAg typically indicate an active hepatitis B virus infection.
HBsAg is a part of the outer layer of a hepatitis B virus cell.
The center of the cell contains the viral DNA, the genes it uses to replicate.
Surrounding the DNA is a protein called hepatitis B core antigen (HBcAg).
However, the immune system is good at getting through this envelope so that kill the virus.
These antibodies develop at different stages of the infection.
Who Should Get Tested?
Your blood may be screened for HBV for many different reasons.
How Is the Test Done?
A HBsAg test is performed by a phlebotomist using a venous blood draw.
The blood is collected into an airtight tube and sent to a lab to be analyzed.
No special preparation is needed prior to the test.
The HBsAg test focuses on the presence or absence of this biomarker.
If HBsAg is detected, the test is positive.
If no HBsAg is detected, the test is negative.
The body produces antibodies to HBsAg as part of the immune response to infection.
A recent hepatitis B vaccination (HepB) can also cause a positive HBsAg test result.
Most labs identify a range between 0.05 and 250 international units per milliliter (IU/ml).
Hepatitis B Treatment
There is no specific treatment for an acute HBV infection.
Infections that last longer than six months are considered chronic.
The World Health Organization recommends treating chronic HBV infections with antiviral medication.
Hepatitis B is spread through contact with blood, semen, and other body fluids from an infected person.
Vaccination
In Newborns
HBsAg testing is routinely performed during pregnancy.
This is to identify and treat infants at risk for contracting hepatitis B during vaginal or C-section delivery.
Prompt treatment in the first 12 hours of life can prevent hepatitis B transmission from mother to child.
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