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Alternative Names Return to topTiter - antibodies; Serum antibodies
Definition Return to top
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 Return to top
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 Return to top
No special preparation is necessary for this test.
How the Test Will Feel Return to top
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 Return to top
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:
Normal Results Return to top
Normal values depend on the antibody being tested. If your health care provider is testing for antibodies against your own tissue, then the normal value would be zero or negative. In some cases, a normal level is below a certain, specific number.
If your health care provider is testing to see if an immunization brought your antibody titer up to a preventive level, then the normal result depends on the specific value for that immunization.
Negative antibody tests can help rule out certain infections.
What Abnormal Results Mean Return to top
If your health care provider is testing for antibodies against your own tissue, abnormal results would show a positive antibody titer. Depending on the strength of the titer, this could mean that your immune system is fighting its own tissue, cells, or substances.
If your health care provider is testing to see if your immunization brought your antibody titer up to a preventive level, an abnormal result would indicate that your body has not mounted an adequate response against the immunization, and you are not adequately protected from the disease.
A positive antibody test to infectious agents such as viruses can determine if you have a specific infection.
Low levels may also occur if you have an immune deficiency.
Risks Return to top
Veins vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Risks associated with having blood drawn are slight but may include:Update Date: 5/6/2008 Updated by: Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.