What do the test results mean?

The meaning of the results depends on why the test was done. If the test was done to see if a person has immunity to a disease:

A person with an autoimmune disease will have an abnormally high level of antibodies. Knowing the exact type of antibody can often help determine which disease is present.

If a healthcare provider suspects a certain infection, he or she may order this test when the person is first seen. A second test done a week or two later can help determine if the infection is or was present. When an infection first starts, the level of antibodies against the infection is usually low. This is because the immune system has just become aware of the infection. A week or two later, the immune system is on the attack. It is making a lot of antibodies against the infection. This causes the antibody level to be much higher.

In other cases, a healthcare provider may already know a person has an infection or disease. An antibody titer may be ordered to see if the condition responds to treatment. In this case, the test is done before treatment is started. After treating the condition for a certain amount of time, the test can be done again. In some conditions, the level of antibodies goes down over time if the treatment worked or is working.