Antibodies are protein compounds made and secreted by white blood cells that recognize and attack viruses, bacteria and other foreign substances in the body. They are also called immunoglobulins and are found in the blood, spinal fluid and other areas of the body. The antibody binds to the antigen, which is the harmful or foreign substance. In autoimmune disorders, the body may make antibodies against its own cells. Lab tests to measure the amounts and types of antibodies in the blood can show the level and type of infection or disease in the body. To test antibodies, blood is drawn from the arm or the back of the hand and sent to a laboratory. There are several types of testing for antibodies.
Antibody Titer
An antibody titer is a lab test that shows the presence and measures the levels of antibodies in the blood. This test can reveal some past infections such as chicken pox because the antibodies to this virus will remain in the body even after the infection. Health care providers often use an antibody titer test to determine which immunizations a patient needs. MedlinePlus, a publication of the National Institutes of Health, lists other uses for this test, including the presence and severity of autoimmune diseases such as systemic lupus erythrematosus, the need for booster vaccinations, and the presence of infections such as viral hepatitis and mononucleosis. Negative antibody titer tests can also help rule out certain infections.
Antinuclear Antibody Test
An antinuclear antibody, or ANA, test is used by doctors to screen patients for autoimmune diseases such as lupus and rheumatoid arthritis. In these diseases, the immune system overreacts and recognizes the body's own tissues as foreign, developing antibodies against them. An ANA test is used along with a patient's clinical history to determine if there is an autoimmune disease. Symptoms of these diseases include fatigue, fever, joint pain, skin rashes and swelling.
Thyroid Antibody Testing
LabTestsOnline.org explains that thyroid antibody tests are specifically used to help diagnose autoimmune thyroid diseases. These tests are often used along with other tests for thyroid hormones such as T3, T4 and TSH to determine the cause of thyroid dysfunction. Types of autoimmune thyroid diseases include Hashimoto's thyroiditis in pregnant women and Graves' disease. Patients with thyroid cancer may also have slightly elevated levels of thyroid antibodies.
