HBs – indications, course and preparation for the test. HBs standards

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HBs, and specifically the HBs antigen, is a particle indicative of HBV infection. This could mean you are at risk of getting hepatitis B (hepatitis B). The presence of antibodies in a person who has been vaccinated against hepatitis B indicates the degree of protection against infection. The virus that appears in the blood can be detected approximately 30 days after infection.

Hbs antigen is detected in people with viral hepatitis. As a result, it is the main source of confirmation of HBV infection (HBs antigen, more specifically HBsAg, is a protein on the surface of HBV).

When it becomes infected, the immune system starts producing anti-HBs antibodies to fight the virus. The time of activation of the antigen varies, it happens that it can be detected after two weeks, but sometimes it becomes active only after 30 or even 50 days. The extinction takes place 2 to 4 months after the onset of symptoms.

See also: How does the immune system work?

HBs and hepatitis B

Hepatitis B infection can occur either parenterally (due to contact with contaminated blood), or via sexual and perinatal route. The first symptoms may appear after about 2-3 months, including abdominal pain, fatigue, nausea, vomiting, muscle and joint pain. In the case of acute hepatitis B, it can be referred to as jaundice-free, jaundice or cholestatic. If there is uncomplicated acute inflammation, the patient may recover in less than 6 months.

Very rarely, hepatitis B occurs in the form of hyperacute or fulminant, with acute liver failure, which results in the patient’s death. Sometimes the acute form can progress to the chronic form, which in turn can lead to cirrhosis of the liver. The most vulnerable are newborns and infants whose mother is in the highly infectious phase during childbirth, therefore it is crucial to conduct screening tests in the form of HBsAg determination in pregnant women (thanks to which it is possible to apply proper immunoprophylaxis to protect the newborn from infection).

Interestingly, in pregnant women with acute hepatitis B, premature birth is common.

HBs – indications for the examination

The indications for the HBs test are, among others:

  1. suspected HBV infection (especially in people who have contact with blood, i.e. doctors, nurses, paramedics),
  2. pregnancy (the test is performed at the beginning of pregnancy, as part of the viral panel determining the mother’s health status and potential risks to the baby, and at the end of the third trimester, to ensure that the doctor is sure that the mother has not been infected with HBV, and this is needed for immunization newborn baby against hepatitis B),
  3. diagnostics of liver diseases (symptoms such as: digestive problems, ailments in the right hypochondrium, yellowing of the skin or conjunctiva),
  4. monitoring of antiviral therapy,
  5. blood donation or organ donation,
  6. evaluation of the effectiveness of vaccination against hepatitis B (antibodies are tested about 4 weeks after the last dose of the vaccine),
  7. before a planned surgery, blood transfusion, tooth extraction or other procedures that violate the continuity of tissues,
  8. newborn diagnosis,
  9. periodic control of the protective level of antibodies 5 years after vaccination.

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HBs – how does infection occur?

Infection can occur, for example, through sexual intercourse (the virus is transmitted through body fluids) or parenterally, i.e. through contact with infected blood, through non-sterile needles and surgical instruments contaminated with blood of an infected person, and sharing equipment while using drugs.

In addition, infection can occur during childbirth from a previously infected mother.

Also check: Without kissing and with a mask. This is what safe sex should be like in a pandemic

Hbs – who should do the test?

HBs antigen testing should be performed by people who:

  1. there are risk factors for HBV infection (unprotected sexual intercourse, frequent changes of sexual partners, intravenous drug use, the presence of chronic kidney disease, diabetes, age over 60),
  2. chronic liver disease of unknown etiology was found,
  3. are taking chemotherapy or other drugs that reduce immunity,
  4. symptoms of acute or chronic HBV infection appear.

See also: Doctors: Chronic kidney disease is usually caught too late

HBs – standards

In the case of HBs testing, 2 results are possible:

  1. negative (HBs-) – means no virus infection,
  2. positive (HBS +) – indicates the presence of the virus antigen in the blood.

The HBs test involves taking a blood sample from a vein in the elbow fossa. In children, blood is drawn after a small incision is made in the skin.

It should be noted that the concentration of HBs antigen in the blood is highest in the period from 4 to 12 weeks after infection, and it decreases along with the healing process, to disappear completely after 2 to 4 months.

Conducting the HBs test requires prior preparation from the patient.

  1. You do not have to go to the examination on an empty stomach.
  2. Approximately 12 hours before taking the blood sample, you should eat an easily digestible meal.
  3. Sit down and rest for a few minutes before the test.

Before starting the blood sample collection, the patient may report: tendency to faint when taking blood.

There are no special requirements for patient behavior immediately after HBs testing. The recommendations are standard, i.e. for 5-7 minutes you should apply pressure to the blood sampling site and avoid any physical exertion with the hand from which the blood sample was taken for several hours.

HBs – interpretation of results

In the case of the HBs antigen, there are two situations: either the patient has the antigen or not.

In the absence of the HBs antigen in the blood, it can be concluded that the patient has not been exposed to the virus. In the course of acute hepatitis, HBsAg disappears when antibodies specific for the antigen: anti-HBs appear in the blood. Anti-HBs antibodies are detected in the blood 2-4 weeks after the disappearance of HBsAg.

If the presence of HBsAg is longer than 6 months from the symptoms of acute hepatitis, it is a sign of a chronic infection.

It should be added here that the HBe antigen also belongs to the viral hepatitis antigens. In addition, PCR methods are used in the complete diagnosis of viral hepatitis, i.e. a test to detect DNA (nucleic acid – viral genetic material). This test is performed as an additional form to determine the susceptibility of HBV to drugs. At the same time, PCR makes it possible to predict the body’s response to therapy.

Possible complications after HBs examination

There is no information on the possible complications after the examination.

HBs – examination during pregnancy

HBs testing is one of the basic tests performed during pregnancy and should be performed between the 33rd and 37th week of pregnancy. This is due to the transmission of HBV through body fluids (blood, serum, exuding and exuding fluids, semen, saliva, vaginal secretions). Women need to be aware of the risk of contracting her own baby during pregnancy or childbirth. It is worth adding that the presence of the virus, to a small extent, is also detected in breast milk, tears, urine and sweat.

If a pregnant woman is a carrier of the HBs antigen, her baby receives immunoglobulin at birth, which contains high levels of anti-HBs and anti-HBc antibodies. On the first day, every child is routinely vaccinated against hepatitis B.

See also: What does thick saliva show?

HBs and the diagnosis and prevention of hepatitis B infections

In the case of diagnosis of hepatitis B infections, it is mainly based on serological tests and determination of HBsAg and HBeAg viral antigens in the blood serum, as well as anti-HBc, anti-HBs and anti-HBe antibodies in IgM and IgG classes and the detection of genetic material in the blood HBV DNA virus.

In the course of infection, the first symptom is the presence of the HBsAg antigen, then the presence of HBeAg and HBV DNA can be detected (the presence of the last two indicates high infectivity). HBs and HBe antigens disappear with time, but if they persist for more than 6 months, the infection becomes a chronic process.

When it comes to antibodies, the first ones in the course of infection are anti-HBc IgM antibodies, which disappear after some time, to be replaced by IgG anti-HBc antibodies, which in turn can remain in the blood serum for years. When HBe goes away, anti-HBe antibodies are detected and disappear over time. Anti-HBs antibodies appear 4-6 months after infection, but, like anti-HBc IgG, persist in the blood serum for years.

Depending on the combination of markers, there are different stages of the disease. It should be remembered that if HBs antigen is detected in the blood, we are dealing with acute hepatitis B, chronic hepatitis B or chronic carrier activity. If HBs antigen is detected in a pregnant woman, it is an indication for postpartum delivery, in the newborn not only the standard first dose of hepatitis B vaccine, but also specific immunoglobulin (HBIG) containing high levels of anti-HBs and anti-HBc antibodies, which will provide additional protection for your child against infection and viral hepatitis.

If anti-HBs antibodies are detected in the blood serum, this indicates that you have had hepatitis B or have been vaccinated against hepatitis B. A high concentration of antibodies means that the person is immune to the disease.

Hbs – cost of the test

The HBs test performed by the National Health Fund is free of charge. However, if the tested HBs are to be made privately, the cost is about PLN 20-30, depending on the laboratory.

However, it should be borne in mind that in the case of a positive HBs result, treatment can only be planned and implemented by a doctor. That is why it is so important to consult a specialist as soon as possible in such a case.

See also: Online medical advice at the National Health Fund. Where to call to consult a doctor? [WE EXPLAIN]

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