What is the primary purpose of the indirect Coombs test?

The primary purpose of the indirect Coombs test is to identify Rh antibodies against red blood cells (RBCs) in a patient's serum. This test is particularly important in the context of blood transfusions and pregnancy. When a patient has been sensitized to Rh-positive blood (for example, through a previous transfusion or an Rh-negative mother carrying an Rh-positive fetus), their immune system may produce antibodies against the Rh factor.

During the indirect Coombs test, the serum from the patient is mixed with Rh-positive red blood cells. If the patient's serum contains antibodies against Rh-positive RBCs, agglutination will occur, indicating the presence of these antibodies. This information is crucial for determining potential hemolytic reactions in transfusions or assessing the risk of hemolytic disease of the newborn in pregnant women.

Recognizing the primary function of the indirect Coombs test is essential for medical professionals, as it influences clinical decisions regarding transfusions and the management of pregnancies involving Rh incompatibility.