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Antibody titer

Definition

Antibody titer is a laboratory test that measures the level of antibodies in a blood sample.

The antibody level in the blood tells your doctor whether or not you have been exposed to an antigen or something that the body thinks is foreign. The body uses antibodies to attack and remove foreign substances.

Alternative Names

Titer - antibodies; Serum antibodies

How the test is performed

A blood sample is needed. For information on how this is done, see: Venipuncture

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
  • If you need a booster immunization
  • Whether a previous vaccine helped your immune system protect you against the specific disease
  • If you have had a recent or past infection such as mononucleosis or viral hepatitis

Normal Values

Normal values depend on the antibody being tested.

If the test is being done to look for antibodies against your own body tissues, then the normal value would be zero or negative. In some cases, a normal level is below a certain, specific number.

If the test is being done to see if a vaccine fully protects you against a disease, then the normal result depends on the specific value for that immunization.

Negative antibody tests can help rule out certain infections.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Abnormal results depend on which antibodies are being measured.

Abnormal results may be due to:

  • Autoimmune disease
  • Failure of a vaccine to fully protect you against a certain disease
  • Immune deficiency
  • Viral infections

What the risks are

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:

  • Excessive bleeding
  • or feeling light-headedFainting
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

References

Orenstein WA, Atkinson WL. Immunization. In: Goldman L,Schafer AI, eds. . 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 17.

Pisetsky DS. Laboratory testing in the rheumatic diseases. In:Goldman L, Schafer AI, eds. . 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 265.

Encyclopedia content is provided as information only and not intended to replace the advice and instruction from your personal physician.