Viral hepatitis B
Chronic Viral Hepatitis B is a chronic inflammatory disease of the liver with diffuse changes, caused by the hepatitis B virus (HBV) and persisting for six months or longer without signs of improvement.
Approximately two billion people worldwide have been infected with hepatitis B at some point in their lives, and 360 million of them have developed chronic infection. The incidence rates per 100,000 population vary significantly across Europe: from 0.5–4 cases in Germany and Italy to 21–40 in "newer" European countries, including Ukraine.
HBsAg — the surface antigen of the hepatitis B virus — is the primary marker for both acute and chronic forms of the disease. It is a protein molecule (lipoprotein) responsible for the virus’s ability to adsorb onto hepatocytes. Once the virus integrates into the genome of liver cells, they begin producing viral DNA and proteins, including new HBsAg molecules that enter the bloodstream.
In most cases, HBsAg appears during the incubation period and can be detected in blood up to 5–6 months after acute infection onset.
Persistent presence of HBsAg in the blood for more than 6 months indicates a possible transition of the infection into a chronic phase. In some cases, HBsAg may remain detectable for life. This antigen has the potential to activate cellular proto-oncogenes, and after a long period (more than 20 years), it may lead to the development of hepatocellular carcinoma (liver cancer).
Besides complete viral particles, the blood of infected individuals also contains smaller non-infectious particles carrying HBsAg. All these HBsAg-containing particles share a common antigenic determinant — the target for immune response.
Detection of HBsAg in blood serum indicates an ongoing hepatitis B infection. HBsAg is the first immunological marker of HBV infection and appears in the blood several weeks before clinical symptoms such as jaundice occur.
In case of acute infection, HBsAg remains detectable for 1–4 months and then disappears. If HBsAg persists beyond 6 months, the infection is considered chronic. Approximately 5–10% of adults and 90% of newborns are unable to clear the virus after infection and become chronic carriers of HBsAg.
Among HBsAg carriers, about one-third develop chronic hepatitis, which may progress to cirrhosis and, in some cases, hepatocellular carcinoma (liver cancer).
Vertical transmission from mother to child occurs in approximately 20% of pregnant women who are HBsAg positive, and in nearly 60% of those who contract the infection during pregnancy. Since the frequency of vertical transmission varies depending on geographical region and population type, it is believed that susceptibility to intrauterine infections depends on the specific strain of the virus and the genetic structure of the population. Pregnant women with a positive HBsAg result require further diagnostic testing.
The introduction of national vaccination programs against hepatitis B has significantly reduced the spread of the virus among the general population.
Main indications for ordering the test:
- Elevated levels of ALT and AST;
- Clinical signs of acute or chronic viral hepatitis, chronic liver diseases, or bile duct pathologies;
- Examination of contacts within family or workplace settings;
- Preparation for hepatitis B vaccination;
- Examination of patients undergoing frequent parenteral procedures;
- Preoperative preparation and hospitalization planning;
- Pregnancy and pre-pregnancy check-up;
- Screening of blood donors and individuals from risk groups (healthcare workers, children born to HBsAg-positive mothers);
- Unprotected sexual contact and frequent change of sexual partners;
- Intravenous drug use.