Hepatitis A virus (HAV), total antibodies
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Why this test?
For the diagnosis of hepatitis A;
For differential diagnosis of diseases occurring with jaundice.
In what cases is it prescribed?
In the presence of clinical signs of hepatitis: abdominal pain, headache, unmotivated weakness, nausea, fever, diarrhea, jaundice, darkening of the color of urine, loss of appetite and weight;
When an increase in the level of liver enzymes (more often in the range of 500-5000 IU/l, ALT to a greater extent than AST) and bilirubin is accidentally detected, especially in people from hepatitis A risk groups.
Hepatitis A virus (HAV, from the English Hepatitis A virus) is an enveloped RNA-containing virus from the Picornaviridae family that causes clinically expressed or asymptomatic hepatitis in humans. Unlike hepatitis B and C, HAV is usually an acute infection that gradually heals completely. There are no known cases of chronic viral shedding or chronic hepatitis A, but relapses, fulminant forms and severe complications of this disease have been described.
The clinical picture of viral hepatitis A does not have any characteristic features to distinguish this disease from other viral hepatitis or other diseases of the hepatobiliary system. Abdominal pain, nausea, fever, diarrhea, jaundice, darkening of urine color, loss of appetite and weight are most often observed.
The main role in the differential diagnosis of hepatitis A belongs to laboratory methods, primarily the detection of antibodies to HAV in the blood. As with many other infectious diseases, the immune response to HAV involves the production of early (IgM) and late (IgG) immunoglobulins. IgM can be determined in the blood approximately 5-10 days after infection.
Early antibodies persist up to 4-6 months after the disease, but their titer is so low that, as a rule, it is impossible to detect them using standard diagnostic systems at such late stages. It should be remembered that IgM can normally be detected in patients who have recently received a vaccine against hepatitis A.
Late IgG antibodies can be determined in the blood starting from the 2nd week after infection. These antibodies persist for life after an infection or vaccination. Determination of IgG may be useful for identifying individuals not immunized to HAV and prevention of this disease.
The study is characterized by high sensitivity and specificity (about 95%). However, false positive and false negative results are possible. Yes, IgM is not detected in the blood in the first few days after infection.
The greatest diagnostic value is a positive test result in a patient with symptoms of the disease.
A positive result in a patient without symptoms of the disease and without risk factors for HAV infection (persons who live with a patient with hepatitis A, employees of kindergartens, recipients of blood products, HIV-infected, persons who use narcotic drugs and some other groups) can tell about a test error.
As a rule, when hepatitis A is suspected, the analysis for specific antibodies to this virus is supplemented with analyzes for markers of other viral hepatitis (HCV, HBV), liver enzymes (ALT, AST), bilirubin, and alkaline phosphatase, and the results of the studies are evaluated as a whole.