What Is an Antibody Test?

An antibody test, or antibody titer, detects the presence and measures the amount of antibodies in the blood. The amount of antibodies in the blood can determine if booster immunizations are needed or if a recent immunization was strong enough to prevent a disease. In some cases, the antibody test is used to identify past infections.

What Is an Antibody?

• The immune system makes proteins called antibodies that bind to bacteria, viruses and other foreign substances. Antigens are chemicals existing on the surface of viruses and bacteria. Antibodies are created by the immune system specific to the foreign body. The surface of each living cell has a different protein marker. Once created, some of these antibodies remain in the immune system, ready to attack a reoccurrence of exposure to the virus or bacteria. Often, they can protect the body from becoming infected, and the person is considered immune. Antibodies that fight viruses like hepatitis, mononucleosis, HIV and chicken pox can be detected by a blood test.
  Things go wrong when the body identifies normal tissue as a foreign substance. The immune system creates antibodies against the tissue, and normal cells are destroyed, causing autoimmune disease or autoimmune response.

Antibody Test

• The antibody test is done by a blood draw from a vein on the inside of the arm. No preparation is needed from the patient, but blood thinning medications, bleeding or clotting problems should be discussed with the lab technician prior to testing.

Antibody Test Results

• A negative blood test means that no antibodies were found. This is the normal result. An abnormal result would be a positive reading.
  Systemic lupus erythematosus, lymphoma, advanced stage cancer, hemolytic anemia, mycoplasma infection, or infectious mononucleosis could be the underlying causes for a positive antibody test as well as an incompatible blood transfusion. An antibody test is also used before a blood transfusion to test for compatibility. The test is also used for Rh factor testing.

Factors Impacting Antibody Test Results

• Several factors can affect the antibody test results. Past blood transfusions or a recent pregnancy can affect antibody identification. Medications such as insulin, tetracycline, cephal osporins, tuberculosis medications and any medication with sulfa may also interfere with the results of an antibody test.
  A contrast material for a recent X-ray or a dextran injection may also render the test useless.

Testing Antibodies on Fingerprints

• British scientists are working to use antibody tests on fingerprints for mass screening for disease. Because the test sample is a fingerprint, there would be no danger of a sample mix-up.
  Antibody testing of fingerprints could also play a part in identifying a suspect whose fingerprint records are not in a database by narrowing the pool of suspects. Drug detection, medications, disease, and even food consumed could help profile the lifestyle of an unidentified criminal through this breakthrough application of antibody testing.
  According to a research team from the University of East Anglia and King's College, they have already been able to tell the difference between the fingerprints of smokers and non-smokers.