Definition of Antibody titer:

Antibody titer is a laboratory test that measures the presence and amount of antibodies in blood. The antibody level in the blood is a reflection of past exposure to an antigen or to something that the body does not recognize as belonging to itself. The body uses antibodies to attack and remove foreign substances.

How the test is performed:

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is 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:

In some situations, your health care provider may check your antibody titer to see if you had an infection in the past (for example, chickenpox) or to decide which immunizations you need.

The antibody titer is also used to determine:

• The strength of an immune response to the body's own tissue in diseases such as systemic lupus erythematosus (SLE) and other autoimmune disorders
• Your need for a booster immunization
• Whether a recent vaccine caused a strong enough response from your immune system to protect you against the specific disease
• Whether you have, or recently had, an infection such as mononucleosis or viral hepatitis