An antibody titer is a test that determines the level and presence of antibodies in the blood. Antibodies are produced by a person's immune system in order to remove and attack foreign substances. An antibody titer generally is conducted like any standard blood test.
An antibody titer is performed for several reasons. The test can determine whether an individual has or recently has had an infection such as mononucleosis or viral hepatitis. It also might indicate whether an immunization, such as a booster shot, should be performed. It also can show whether a recent vaccine will be strong enough to protect against disease.
One common antibody titer is the Coombs test. It is administered in direct and indirect forms. The direct Coombs test is carried out to determine whether there are antibodies attached to an individual's red blood cells. These antibodies usually develop when a person uses drugs excessively or has a disease. Anemia or jaundice normally will be the result of these antibodies.
The indirect Coombs test is used very rarely. This antibody titer detects boundless circulating antibodies in the serum of the blood. The test mainly is done to determine whether an individual could have a reaction to a blood transfusion.
The Coombs test in either form also might be conducted on a newborn child to see whether his or her mother has passed on antibodies during the pregnancy. This is an issue when the mother has Rh-negative blood and the baby has Rh-positive blood. While in utero, antibodies might have traveled through the placenta to the fetus.
The results of an antibody titer usually are accurate. There are times, however, when this is not the case. Some reasons for an erroneous test include a past blood transfusion, a recent X-ray or use of certain medications.
There are no preparations that a person needs to take before an antibody titer is administered. The procedure involves drawing blood from a vein, normally on the back of the hand or the inside of the elbow. In infants or younger children, a lancet might be used. There are virtually no health risks when a person has a blood sample drawn from a vein.
As with anytime blood is drawn, a person might feel pain, but it usually is on a minor level. There might be some throbbing after an antibody titer is finished, as well as bruising or swelling at the spot where the needle was injected. These problems usually can be alleviated by an individual maintaining pressure on the site for several minutes.