Final answer:
An Indirect Coombs' Test is necessary for detecting non-ABO antibodies in the serum of pregnant women or before blood transfusions. It helps identify antibodies that may cause hemolytic reactions in newborns or transfusion reactions in patients. The test is performed in vitro, and a positive result indicates the presence of these antibodies.
Step-by-step explanation:
Understanding the Need for an Indirect Coombs' Test
An Indirect Coombs' Test (also known as the indirect antiglobulin test or IAT) is needed when there is a possibility that a person may have antibodies against red blood cell antigens beyond the A and B antigens. This test is particularly relevant for pregnant women and individuals before receiving blood transfusions. The IAT is performed in vitro and is important for detecting these non-ABO antibodies, which, if present in the patient's serum, could lead to hemolytic disease of the newborn or transfusion reactions. The test involves mixing the patient's serum with pooled type O red blood cells and observing whether agglutination occurs, indicating the presence of antibodies.
Women who have had multiple pregnancies, or patients who have received multiple blood transfusions, might need an Indirect Coombs' Test due to possible exposure to different antigens and subsequent antibody formation. Furthermore, conditions like hemolytic anemia, certain infections, and drug reactions can also necessitate this test, as referenced by the direct Coombs' test, which detects if antibodies are actively binding to the person's own red blood cells.
The IAT operates by adding a few drops of Coombs' reagent, which contains antihuman antibodies, into the patient's blood sample. If the patient has antibodies against the donor red blood cells, hemagglutination will be observed. If negative, Coombs' reagent may be added to confirm results and visualize the antibody-red blood cell interaction.