An anti-HAV test detects specific proteins, known as antibodies, that your immune system produces in response to the Hepatitis A virus (HAV). Hepatitis A is a liver infection. These tests help determine if someone has been exposed to the virus or has developed protection against it.
The Role of Anti-HAV Antibodies
The immune system generates different types of antibodies, each with a distinct role in fighting off infections and providing future protection. For Hepatitis A, two primary types of antibodies are measured: Immunoglobulin M (IgM) and Immunoglobulin G (IgG). The presence of one or both of these types tells a different story about a person’s history with the virus.
Anti-HAV IgM antibodies are the first responders to an initial Hepatitis A infection. They become detectable in the blood within approximately two weeks after exposure. These antibodies signal a new or recent infection, generally remaining at elevated levels for about two to six months before declining to undetectable levels, though they can persist for up to a year in some cases.
Anti-HAV IgG antibodies develop later than IgM antibodies. These are often referred to as “memory” antibodies because they provide long-term immunity against future Hepatitis A infections. IgG antibodies rise quickly once the virus is cleared and can remain in the body for many years, offering lasting protection from either a past infection or successful vaccination.
Positive Anti-HAV Test Results
A positive anti-HAV test result indicates Hepatitis A antibodies in your blood, but the specific interpretation depends on which type of antibody is detected. If your test is positive for anti-HAV IgM, this signifies a current or recent acute Hepatitis A infection. These antibodies are a reliable marker for active disease.
When a test is positive for anti-HAV IgG but negative for anti-HAV IgM, this indicates long-term immunity to the Hepatitis A virus. This protective immunity can result from a past, resolved Hepatitis A infection. It also means that the person has developed immunity from a successful Hepatitis A vaccination.
Screening tests measure “Total Anti-HAV,” which detects both IgM and IgG antibodies together. A positive result on a total anti-HAV test indicates past exposure to the virus or immunity from vaccination, but it does not differentiate between a current infection and past immunity. If a total anti-HAV test is positive, healthcare providers recommend further, more specific testing for IgM and IgG individually to determine the status of the infection or immunity.
Negative Anti-HAV Test Results
A negative anti-HAV test result means that no detectable Hepatitis A antibodies were found. This indicates that you do not have a current Hepatitis A infection and have not had one in the recent past. It also signifies a lack of immunity to the Hepatitis A virus, making you susceptible to contracting the infection if exposed.
A negative result suggests that you have neither been previously infected with Hepatitis A nor have you received the Hepatitis A vaccine. In some instances, a negative result might occur if antibodies have not yet reached detectable levels. Given the susceptibility, a healthcare provider may recommend the Hepatitis A vaccine to provide protection.