What does the indirect Coombs test detect before a transfusion?

Before a blood transfusion, the indirect Coombs test is used as part of the compatibility screening process to detect antibodies in the recipient's serum that could react with antigens on the donor's red blood cells.12

By identifying these antibodies, the test helps prevent life-threatening immune destruction—known as a hemolytic transfusion reaction—that could occur if incompatible blood were transfused. Along with testing the recipient's serum against the donor's cells, the indirect Coombs test serves as an essential screening measure to ensure the safety and compatibility of the blood before it is administered.12