Direct Antiglobulin Test

The direct antiglobulin test (DAT) is used to detect the cause of hemolytic anemia. It is also used to find the cause of transfusion reactions, and to diagnose hemolytic disease of the newborn. This test may be done if there are symptoms suggesting hemolytic anemia, such as unusual tiredness, unexpected difficulty breathing when exercising, and unusually dark urine, or if your hemoglobin or hematocrit are unexpectedly low, or if you have had a blood transfusion recently and are experiencing any of the above problems. The DAT is ordered when hemolytic anemia, hemolytic disease of the newborn, or a transfusion reaction is suspected.

This test looks for antibodies attached to your red blood cells. An example would be getting a transfusion and your body recognizes that the blood is not your own. Your body then produces antibodies against those foreign blood cells. Another example would be a newborn with blood more like the fathers. The mother would then produce antibodies attacking the newborn's blood. This is the basis of Rh disease when the mother is Rh negative and the baby is positive.

When a baby inherits antigens from its father that are not on its mother's red blood cells (RBCs), the mother can produce antibodies against the foreign antigens on her baby's RBCs inside the womb. This can cause hemolytic disease of the newborn. This usually does not affect the first baby but does affect subsequent children. In addition, some people make antibodies to their own RBCs. These antibodies are produced in autoimmune diseases and are called autoantibodies. In all of these situations, antibodies attach to the RBCs and can result in their destruction.

PREPARATION FOR TEST

No preparation or fasting is necessary for the test. A blood sample will be taken from a vein in your arm by inserting a needle.

NORMAL FINDINGS

Negative: no agglutination

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.

MEANING OF TEST

Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.

OBTAINING THE TEST RESULTS

It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.