These include (a) serum for antibody detection test and (b) liver, bile, stool, and blood for HAV antigen and genome.
Hepatitis A virus is present in stools during 2 weeks prior to the onset of jaundice and up to 2 weeks after the onset of jaundice. The virus can be demonstrated in the stool during this period by using immunoelectron microscopy.
Although the virus has been grown in human and simian cell culture, its isolation by culture of feces in the cell line is not routinely done, because the facilities for growing the virus are not widely available.
Serodiagnosis of HAV infection depends on the demonstra-tion of specific antibodies in the serum. Serological tests demonstrating these anti-HAV antibodies in the serum are the most widely used to confirm the diagnosis of HAV infection. Enzyme-linked immunosorbent assay (ELISA) is the method of choice for detection of IgM and IgG antibodies in the serum. IgM antibody is the first antibody to appear at the onset of symptoms and continues to persist at a high level for 1–2 months. It usually disappears by 4–6 months but occa-sionally persists longer. Hence, demonstration of IgM anti-body is diagnostic of a recent infection. IgG antibody appears in the serum shortly after the appearance of IgM antibodies and usually increases as the IgM level decreases. A fourfold rise in IgG antibody titers is also diagnostic of infection.
Liver function tests are highly useful for supplementing the diagnosis of HAV infection. Hepatitis A virus infection is associated with a consistent increase in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST).
Increase in ALT and AST levels is nearly 4–100 times more than the normal levels. Increase in serum levels of ALT and AST are usually seen 1 week before. The ALT and AST remain at peak level within 3–10 days after the onset of clinical illness. Serum bilirubin level is also increased, and it increases with the appearance of jaundice. Decrease in serum albumin level and prolongation of prothrombin time indicate a severe hepatocellular infection.