Hepatitis B virus (HBV) is an enveloped DNA virus of the family Hepadnaviridae. Hepatitis B (HB) has a long incubation period of 45 to 160 days (average: 120 days).The appearance of symptoms at the acute HB is inversely related to age: less than 1% of newborns and 30%–50% adults develop symptoms, which are loss of appetite, abdominal discomfort, nausea, vomiting, fever and jaundice. In less then 1 % of cases, especially in the elderly, fulminating HB develops, which is mostly fatal due to acute hepatic necrosis.
The acute HB often resolves spontaneously after a 4-8 week of illness. Otherwise, the infection can last for six months or more. This condition is known as chronic HB.
More than 90 % of infected infants, 25–50 % of children infected between 1 and 5 years of age, and 6–10 % of acutely infected older children and adults develop chronic infection. As a result, more than 350 million people in the world today are estimated to be persistently infected with HBV.
In a considerable number of patients, chronic HB may lead to liver cirrhosis and hepatocellular carcinoma. Cirrhosis affects around one in five people with chronic hepatitis B. Of all causes of cirrhosis, approximately one third can be attributed to chronic HBV infection. Transmission occurs by percutaneous and permucosal (through broken skin) exposure to such infective body fluids as blood, vaginal and menstrual fluids, and semen. The main ways of transmission include: vertical- from an infected mother during delivery (rate of transmission around 50%); sexual; horizontal-household contact with an infected person (for example, contact of infected blood with cutaneous scratches), sharing of contaminated injection drug equipment by injection drug users, or unhygienic injection procedures in health-care institutions.
During the clinical laboratory analysis of the different forms of the viral hepatitis B several serologic markers of this disease are detected. This markers are structural antigens of the virus (HBs-antigen and HBe-antigen) and antibodies specific to HBcore, HBs- and HBe-antigens.
HBsAg is the main marker of HBV infection and it is a structural protein that is responsible for virus absorption on the hepatocytes. It is the first marker that appears in blood in 3-5 weeks after infecting. Before appearing the clinical signs and in case of acute hepatitis it is being found in quite high concentrations during some months. If the clinical course is favorable HBsAg disappear in 4-6 months after infecting. If it doesn’t happen, chronic hepatitis is diagnosed.
HBsAg concentration in the blood serum of HBV infected patients can vary in a wide range: from nanograms to hundred micrograms per ml. Elimination of HВsAg from circulation is a criterion of recovery.
Among laboratory methods of detection HBsAg enzyme linked immunosorbent analysis (ELISA) is the most common and highly sensitive one. It is used both for diagnostics of disease and for screening of donor blood to prevent transmission of the hepatitis B.
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