Hepatitis B surface Antigen or HBsAg is detected in the specific type of blood test known as HBsAg test. A high HBsAg often indicates an active Hepatitis B virus infection.

The outermost layer of a Hepatitis B virus cell contains HBsAg. The viral DNA and the genes it requires to replicate are found inside the cell's core. The "envelope" that shields the virus from the body's immune system is made up of HBsAg, which surrounds HBcAg. The immune system is trained properly to absorb this envelope and kill the virus. The lab testing can find surface antigen protein traces in the blood-like debris left behind.

What Is an HBsAg test?

Hepatitis B surface Antigen, a protein on the surface of the Hepatitis B virus, is found via a blood test known as an HBsAg test. An HBsAg positive means that the patients are contagious and have a current or chronic Hepatitis B infection. Along with other tests, the HBsAg test is used to detect Hepatitis B infection and identify those who might benefit from immunization.

Purpose of HBsAg test

HBsAg test is performed in order to detect the virus named Hepatitis B. Once the tests are done, and the findings are out, the doctor will curate an effective treatment plan for HBsAg-positive treatment to eliminate this virus.

When should I get this HBsAG test?

As per the Centers for Disease Control and Prevention (CDC), everybody should be screened for Hepatitis B infection in case of any symptoms such as -

• Abdominal pain
• Dark urine
• Fever
• Loss of appetite 
• Fever
• Nausea and vomiting 
• Joint pain
• Weakness and fatigue 
• Yellowing of the skin and eyes (jaundice)

What happens during the HBsAG test?

A medical professional must take a small sample of blood for a hepatitis titer test. Here’s what happens during the HBsAg test-

• The arm is wrapped with a band by the person performing the test in order to make it easier to locate the veins.
• A tiny needle is then inserted into the vein after the injection site has been cleaned and sterilised. An acute pain could be present, but it should disappear rapidly.
• The test administrator instructs the patient to gently push with a piece of gauze or a cotton ball after the needle is removed.
• The patient is free to go after the area has been bandaged.

There are various HBsAg blood tests that may be taken at home with a fingerpick. The test results will typically be ready in three days.

Procedure for HBsAg Test

The procedure of the HBsAg rapid test depends on the type of test kit used. However, it often entails the following steps-
A needle is inserted into a vein in the arm or hand to draw blood.

• The blood sample is examined in a lab or on the spot with a testing tool.
• Antibodies that react with HBsAg, a sign of Hepatitis B infection, are coated on the test instrument.
• To create a colour shift, the test device is incubated, cleaned, and treated with a substrate and a stop solution.
• Depending on the test kit, the test result is examined visually or by an ELISA reader.

Uses of HBsAg Test

Hepatitis B Virus (HBV) infection can be either acute or chronic and can be detected with this specific test. It aids in deciding whether post-test counselling and care coordination are required, in addition to the requirement of an HBsAg positive treatment plan. The test can also reveal whether a person has an immunity to HBV as a result of an earlier infection or immunisation.

How to prepare for the HBsAg test?

There is no need to prepare for the HBsAg blood test. However, it is advisable to be at the centre 10 minutes before the given time. Also, if the thought of needles or seeing blood makes a patient nervous, they might wish to plan a drive in advance in case they start to feel dizzy.

Values of HBsAg test Results

Three HBsAg blood tests can be performed with just one blood sample as part of a Hepatitis B blood test -

• HBsAg (Hepatitis B Surface Antigen) - A positive test results in Hepatitis B infection and the ability to transmit the disease to others. To determine whether the patient has an acute or persistent infection, more testing is required.
• Anti-HBc or HBcAb (Hepatitis B Core Antibody) - Although a positive test result does not guarantee immunity, it may suggest a past or present Hepatitis B infection. A doctor must evaluate the results of the other two tests in order to interpret a positive result.
• HBsAb (Anti-Hepatitis B Surface antibody) - A positive test results in protection from Hepatitis B from either prior infection or immunization, albeit it's still risky.

These tests, if done together, can reveal the Hepatitis B status and if the patient needs to get immunized. Depending on whether the test results are above or below the cutoff threshold, the test will give a negative or positive result for each category.