Antibody titer

Alternative names:

serum antibodies; titer - antibodies

How the test is performed:

Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

How to prepare for the test:

No special preparation is necessary for this test.

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

The antibody level in the blood is a reflection of the body's past experience or exposure to an antigen, or something that the body does not recognize as self. Every living cell has different protein markers on its surface called antigens, and the body's immune system identifies those cells that are not part of its structure by those surface proteins.

Occasionally, the body makes an error and begins to recognize its own tissue as being non-self, or foreign. This leads to a mounting immune response against that tissue type, cell, or substance that is part of the body. The body uses antibodies to attack the foreign matter, or the self matter that it recognizes as self.

Levels of antibodies in the blood are measured with this test, and indicate that the body has come into contact with a particular antigen, or that the body's immune system has reverted, and recognizes it's own matter as foreign. This would be evident if there was a titer of antibodies against the bodies own tissue which is the case with some types of diabetes mellitus, SLE, and other autoimmune disorders.

Checking an antibody titer is also useful if your health care provider wants to check and see if you need a booster immunization, or if a recent administration caused a strong enough response from the immune system, bringing your antibody titer against that particular disease up to a preventative level.