HBs antigen testing
HBs antigen is a diagnostic indicator thatwhose assay makes it possible to detect the hepatitis B virus. The test is performed in order to diagnosis of hepatitis B virus infection and to monitor the course of the disease.When is it a good idea to do the test?
HBs antigen - what is it?
HBs antigen[1] is a type of specific protein found on the surface of the HBV virus. The presence of this protein in a blood sample undergoing testing constitutes what is known as the 'protein of choice'. marker for viral hepatitis, an indicator of ongoing hepatitis B infection.
It is worth knowing that the HBs antigen appears between 6 and 16 weeks after infection, long before visible symptoms of ongoing infection develop.
What do you need to know about hepatitis B?
Hepatitis B, or hepatitis Bis a disease caused by the HBV virus that is common throughout the world. Acute infection is usually asymptomatic. Only in some cases does it produce such obvious symptoms as yellowing of the skin. In the chronic phase, it may lead to progressive destruction of the liver parenchyma, which may result in cirrhosis or hepatocellular carcinoma.[1].
In cases where the infection manifests symptoms, these may be completely non-obvious, i.e.[2]:
- increased fatigue,
- nausea and vomiting,
- abdominal pains,
- joint and muscle pains,
- general deterioration in well-being.
In some cases, hepatitis B gives obvious, easily recognisable signals, which include:
- yellowing of the skin coating or whites of the eyes,
- clear, discoloured stool,
- very dark (brown, sometimes almost black) urine,
- persistent itching of the skin.
In the course of HBV infection, blood counts will show significant increase in plasma bilirubin and aminotransferases.
HBV infection occurs due to contact with blood - both direct contact and through blood-contaminated surgical instruments or needles and during sexual intercourse with a sick person. The virus can also be transmitted from mother to child during childbirth.
When is it a good idea to perform HBs antigen determination?
In Poland, as part of hepatitis B prevention, vaccination against the virus has been one of the mandatory vaccinations for newborns for more than 30 years. Tests for HBs antigen are most commonly performed[3]:
- in pregnant women,
- before assisted reproduction procedures (in vitro i insemination),
- in people who wish to donate blood, marrow or organs,
- in high-risk groups (i.e. medical professions, cosmetics, etc.),
- for proper monitoring of the antiviral treatment implemented,
- for the diagnosis of hepatitis B in people showing symptoms of infection.
For women who are pregnant or preparing for motherhood, it is important to know if they are infected with HBV because of the possibility of vertical transmission of the virus from mother to child during childbirth.
In the event of a positive result testing for HBs antigen during pregnancy the newborn of an infected mother receives immunoglobulin and vaccination against HBV immediately after birth[4][5].
How to prepare for HBs testing?
HBs testing is performed on the basis of a venous blood sample. If this is the only test performed, or if only antibody tests are performed (e.g. when performing a viral pregnancy panel), no special preparation necessary.
If the test is combined with other tests requiring special procedures prior to blood collection (e.g. being fasted), then you should prepare as for the other tests.
HBs antigen - interpretation of results
With the HBs antigen test, there is not a long wait for the result - it is usually available the very next day. This test is a qualitative test, which means that the presence or absence of HBs antigen is determined. It can therefore indicate 2 results[6]:
- HBs antigen non-reactive (negative) - which means that there is no viral protein in the sample and therefore no infection,
- HBs antigen reactive (positive) - indicating the detection of an antigen in the collected blood.
A positive test result requires urgent consultation with a doctor. It should also be noted that false positive may occur in pregnant women and in the case of incorrect preparation of the blood sample for testing. Therefore, the doctor may order retesting.
Also in the case of a negative result, it can happen that it is false. This happens in some rare HBV mutations, which make the HBs antigenic determinants needed for a correct serological reaction absent, so that no reaction takes place and the test appears negative. Also, the presence of heterotrophic antibodies can give a false negative result.
Therefore, especially if symptoms of hepatitis B are present, despite a negative result, it is important to contact the attending physician for further diagnosis[7].
HBs antigen - test price
Cost of laboratory tests is dependent on the clinic chosen and the location. At InviMed clinics, an example price for an HBs antigen test is:
- Warsaw Mokotów - PLN 58,
- Katowice - PLN 50,
- Gdynia - PLN 50.
Bibliography:
- LADA, Olivier, BENHAMOU, Yves, POYNARD, Thierry, et al. Coexistence of hepatitis B surface antigen (HBs Ag) and anti-HBs antibodies in chronic hepatitis B virus carriers: influence of "a" determinant variants. Journal of virology, 2006, vol. 80, no. 6, p. 2968-2975.
- HAEMODIALYSIS, IN. THE WIELKOPOLSKA STATIONS. "HEPATITIS B VIRUS INFECTIONS." PRZEGL EPIDEMIOL 62 (2008): 29-37.
- LAU, George KK, SURI, Deepak, LIANG, Raymond, et al. Resolution of chronic hepatitis B and anti-HBs seroconversion in humans by adoptive transfer of immunity to hepatitis B core antigen. Gastroenterology, 2002, vol. 122, no 3, p. 614-624.
- SIKORA, AGNIESZKA, SIKORA-FUTYMA, A. N. N. A., et LASKOWSKA, MARZENA. MICROBIOLOGICAL TESTS IN PREGNANT WOMEN-STANDARDS OF MANAGEMENT. In : Forum Infections. 2020.
- FLISIAK, Robert, HALOTA, Waldemar, JAROSZEWICZ, Jerzy, et al. Recommendations of the Polish HBV Expert Group for the treatment of chronic hepatitis B in 2018. Hepatology, 2018, vol. 18, p. 10-21.
- KLAMANN, Janusz et SMIATACZ, Tomasz. Diagnostics of viral hepatitis in general practitioner practice. In : Forum of Family Medicine. 2016. p. 66-72.