An anti-hbs test is required to check if you have immunity against the hepatitis B virus, whether acquired through vaccination or after contracting the disease and being cured.
This test is based on the analysis of a small blood sample in which it is verified the amount of antibodies you have against the hepatitis B virus in your bloodstream. Normally, the anti-hbs test is requested together with the HBsAg test, which is the test that determines whether the virus is present in your blood and is therefore used for diagnosis.
What is the test requested
The anti-hbs test is important to evaluate the body's production of antibodies against a protein on the surface of the hepatitis B virus, HBsAg. So, through the anti-hbs examination the doctor can check whether or not you have been immunized against hepatitis B by vaccination, and whether the treatment is effective or if you have been cured after the diagnosis for hepatitis B was confirmed.
While the anti-hbs test is requested to verify you immunity and response to treatment, the HBsAg test is requested by the doctor to determine if you are infected or have had contact with the hepatitis B virus. So, this test is required in order to diagnose hepatitis B.
HBsAg is a protein present on the surface of the hepatitis B virus and is useful for diagnosing acute, recent or chronic hepatitis B. Usually the HBsAg test is ordered in conjunction with the anti-hbs test so that it is possible to check if the virus is circulating in the bloodstream and if the body is acting on it. When you are infected with hepatitis B, the report contains a reagent HBsAg, which is an important result for the doctor, as it is possible to start treatment.
How is done
To do the anti-hbs test is not necessary any preparation or fasting and it is done by collecting a small blood sample, which is sent to the laboratory for analysis.
In the laboratory, the blood goes through a serological analysis process, in which the presence of specific antibodies against the hepatitis B virus is verified. These antibodies are formed after contact with the virus or due to vaccination, in which the organism is stimulated to produce these antibodies, conferring immunity for life.
How to interpret the results
The result of the anti-hbs test varies according to the concentration of antibodies against hepatitis B virus in the bloodstream, and the reference values are:
- Anti-hbs concentration less than 10 mIU / mL - nonreactive. This concentration of antibodies is not sufficient to protect against the disease, it is important that you are vaccinated against the virus. If a diagnosis of hepatitis B has already been reached, this concentration indicates that there has been no cure and treatment is not being effective or is in its early stages;
- Anti-hbs concentration between 10 mIU / mL and 100 mIU / mL - undetermined or satisfactory for vaccination. This concentration may indicate that the person has been vaccinated against the hepatitis B virus or is being treated, and it is not possible to determine if hepatitis B has been cured. In such cases, it is recommended that the test be repeated after 1 month;
- Anti-hbs concentration greater than 100 mIU / mL - reagent. This concentration indicates that the person has immunity against the hepatitis B virus, either through vaccination or curing the disease.
In addition to evaluating the anti-hbs test result, the doctor also analyzes the HBsAg test result. So, when monitoring a person already diagnosed with hepatitis B, a non- reactive HBsAg positive anti-hbs result indicates that the person is cured and that there are no more circulating viruses in the blood. People who do not have hepatitis B also have the same results and anti-hbs concentration greater than 100 mIU / mL.
In the case of HBsAg and anti-hbs positive, it is indicated to repeat the test after 15 to 30 days, as it may indicate a false positive result, formation of immune complexes (immunocomplexes) or infection by subtypes other than hepatitis B virus.