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:
Epstein-Barr virus infection, which is the main cause of infectious mononucleosis
hepatitis A, hepatitis B, hepatitis C, or hepatitis D, which are viral infections that primarily affect the liver
Lyme disease, which is a bacterial infection that can be caught from a tick bite
rubella, or German measles
syphilis, a sexually transmitted disease
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:
Graves' disease, a condition that results in an overactive thyroid gland
Hashimoto's thyroiditis, a condition that results in an underactive thyroid gland
myasthenia gravis, a condition that causes weakness in the muscles
rheumatoid arthritis, which can cause joint inflammation and deformity
systemic lupus erythematosus, a condition that affects many body systems
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 After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.