Typical Serologic Course of Hepatitis A Virus (HAV) Infection

Since both clinically and biochemically, acute hepatitis due to HAV cannot be distinguished from that due to the other hepatitis viruses, serologic tests are necessary for a virus-specific diagnosis.

Diagnosis of hepatitis is made by biochemical assessment of liver function (laboratory evaluation of: urine bilirubin and urobilinogen, total and direct serum bilirubin, ALT (SGPT) and/or AST (SGOT), alkaline phosphatase, prothrombin time, total protein, albumin, IgG, IgA, IgM, complete blood count).
The specific routine diagnosis of acute hepatitis A is made by finding anti-HAV IgM in the serum of patients. A second option is the detection of virus and/or antigen in the faeces.
Virus and antibody can be detected by commercially available radioimmunoassay (RIA), enzyme immunoassay (EIA) and enzyme-linked immunosorbent assay (ELISA) kits. These commercially available assays for anti-HAV IgM and total anti-HAV (IgM and IgG) for assessment of immunity to HAV are not influenced by the passive administration of immunoglobulin (IG), because the prophylactic doses are below detection level.
At the onset of disease, the presence of IgG anti-HAV is always accompanied by the presence of IgM anti-HAV. As IgG anti-HAV persists lifelong after acute infection, detection of IgG anti-HAV alone indicates past infection.
Virus may still be present in the absence of detectable HAV antigen, as demonstrated by the use of more sensitive methods.




References:

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