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DAT & Blood Transfusion Reactions

In a blood transfusion, you receive blood through an intravenous tube. One risk of blood transfusion is delayed hemolytic reaction. The test for a delayed hemolytic reaction is a direct antiglobulin (DAT), or Coombs, test.

  1. Who Needs Testing

    • If you are at risk for delayed hemolytic reaction after receiving a blood transfusion, you may need a DAT test. People at highest risk are women who have had previous pregnancies and people who have had previous blood transfusions. You may have had a blood transfusion if you have had heart surgery, an illness that causes anemia or blood loss, or a bleeding disorder.

    Symptoms

    • Delayed hemolytic reaction can develop from four days to a month after transfusion. The patient may have no symptoms, or have a slight fever. Lab tests may show decreases in hematocrit, increases in bilirubin in the blood, and hemoglobin in the urine.

    How It Works

    • The laboratory technician mixes your blood sample with Coombs' reagent to screen your blood for certain blood antibodies. If this is positive, the next step is to look for immunoglobulin G (IgG) and complement factor C3d using a separate reagent and checking for a color change.

    Interpretation

    • The technician evaluates the results and comes to a conclusion about whether the patient has delayed hemolytic reaction. Considerations include the strength of the color change and patient history and risk factors like previous pregnancy.

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