DefinitionAntibody 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 NamesTiter - antibodies; Serum antibodies
How the test is performedA blood sample is needed. For information on how this is done, see: Venipuncture
How to prepare for the testNo special preparation is necessary for this test.
How the test will feelWhen 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 performedIn 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 disordersIf you need a booster immunizationWhether a previous vaccine helped your immune system protect you against the specific diseaseIf you have had a recent or past infection such as mononucleosis or viral hepatitis
Normal ValuesNormal 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 meanAbnormal results depend on which antibodies are being measured. Abnormal results may be due to:Autoimmune diseaseFailure of a vaccine to fully protect you against a certain diseaseImmune deficiencyViral infections
What the risks areVeins 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 bleedingFainting or feeling light-headedHematoma (blood accumulating under the skin)Infection (a slight risk any time the skin is broken)
ReferencesOrenstein WA, Atkinson WL. Immunization. In: Goldman L,Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 17.Pisetsky DS. Laboratory testing in the rheumatic diseases. In:Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 265.