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HAV_Ab Total

Hepatitis A IgG/IgM

Hepatitis A is a highly contagious liver infection caused by the hepatitis A virus (HAV). When the body is infected with HAV, it defends itself by producing two types of antibodies in sequence: first, IgM, which appears 2 to 4 weeks after infection and is present for 2 to 6 months, then IgG, which appears a few weeks after IgM and is present for the rest of the person’s life. IgG provides long-term immunity (protection), whether due to a prior infection by the virus or due to vaccination. Testing for HAV antibodies Total (IgG plus IgM) is especially useful in confirming an individual’s long-term immunity and the appropriateness of vaccination. The specific anti-HAV IgM test is used mainly to find the cause of an acute or very recent liver disease.

A positive HAV-Ab total test (without isolated testing for IgM) indicates prior HAV exposure but does not rule out acute or very recent hepatitis. About 30% of North American adults over the age of 40 are positive for HAV-Ab total. A negative HAV Ab Total test means there has been no prior exposure to the virus and the hepatitis A vaccination should be administered. A positive IgM test suggests acute or very recent hepatitis A.

Term of the Week

Hot zone

A hot zone is a section of a facility (sometimes an entire facility or even a city district) where there is a high risk of contamination by patients with an infectious disease. All individuals entering a hot zone must respect appropriate protective measures. By analogy, “cold zone” and “warm zone” are used to refer to areas where there is no infected individual or only individuals suspected of having an infection.