What does a positive indirect Coombs test indicate?

A positive indirect Coombs test indicates the presence of antibodies in serum that may react with antigens on red blood cells. This test is primarily used to identify individuals who may have antibodies against specific red blood cell (RBC) antigens, which can be pertinent in various clinical situations, including blood transfusions and hemolytic disease of the newborn.

In the indirect Coombs test, patient serum is incubated with red blood cells that have known antigens on their surface. If the serum contains antibodies against those antigens, those antibodies will bind to the red blood cells. The Coombs reagent, which contains anti-human globulin, is then added to facilitate agglutination if these antibody-antigen complexes are present. The presence of agglutination indicates a positive reaction, thereby confirming the presence of anti-RBC antibodies in the serum.

This is crucial in transfusion medicine because a positive test could signify potential complications from transfusing red blood cells that contain those corresponding antigens. It is important for ensuring compatibility between donor and recipient blood to prevent transfusion reactions.

The other options relate to different clinical scenarios that do not apply specifically to the indirect Coombs test, such as antigens on red blood cells, white blood cell