What Does a Positive IgG Antibody Test for Hepatitis A Virus Indicate?

A positive IgG antibody result for the hepatitis A virus typically indicates a past infection, suggesting that the individual was previously exposed to the hepatitis A virus (HAV). Clinically, diagnosing hepatitis A involves a comprehensive evaluation, including the patient's epidemiological history, clinical symptoms, physical examination, and laboratory findings.

Common symptoms of hepatitis A infection include fever, fatigue, joint pain, abdominal discomfort, diarrhea, nausea, vomiting, and jaundice. These signs often follow a history of exposure, such as consuming undercooked seafood or other contaminated food sources. Liver function tests usually reveal abnormalities, particularly elevated levels of liver enzymes, which support the diagnosis.

One of the most critical diagnostic tools is serological testing for hepatitis A antibodies. If the IgM antibody against HAV is detected, it confirms a recent or acute hepatitis A infection. IgM antibodies typically appear at the onset of symptoms and remain detectable for about four months, although in some cases they may persist for over a year.

On the other hand, IgG antibodies develop during the illness and remain present for life, serving as a marker of previous infection or immunity due to vaccination. However, if two consecutive blood tests show a fourfold or greater increase in IgG antibody levels, this may also indicate a recent infection. In rare cases, both IgM and IgG antibodies may initially test negative early in the infection and only become detectable as the disease progresses, which can be related to the sensitivity of the testing method. Therefore, repeat testing may be necessary when initial results are negative but clinical suspicion remains high.