The antibody titer detects and measures the amount of antibodies in the blood. Antibodies are proteins made by the immune system. These antibodies are made to attack a real or imagined threat. For example, antibodies may be made in some cases to attack bacteria causing an infection. In other cases, however, antibodies may be made to attack a person's own body.

Who is a candidate for the test?

One common function of the antibody titer is to detect antibodies that the body has made to fight off a certain disease. Sometimes this is done to check whether a person has gotten a vaccine against a disease. It can also see if someone has natural immunity due to having the disease in the past. This test may be useful in the diagnosis of the following diseases:

Another common function of the antibody titer is to see if the immune system is creating antibodies to a person's own body. This response occurs in a variety of autoimmune disorders. Following are some examples of autoimmune conditions in which this test may be useful:

The antibody titer also is useful in following the course of known or suspected infections or conditions.

How is the test performed?

To measure the levels of antibodies in the blood, a blood sample is needed. This is usually taken from a vein on the forearm or hand. First, the skin over the vein is cleaned. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them.

A fine needle is gently inserted into the chosen vein and the tourniquet is removed. Blood flows from the vein through the needle. It is collected in a syringe or vial for testing in the lab. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.