The Direct Coombs Test (also known as the Direct Antiglobulin Test, DAT) is a laboratory test used to detect antibodies or complement proteins attached to the surface of red blood cells. This test is commonly used to diagnose conditions such as autoimmune hemolytic anemia, where the immune system mistakenly attacks its own red blood cells, or hemolytic disease of the newborn, where antibodies from the mother attack the baby’s red blood cells. The test involves mixing a patient’s red blood cells with Coombs reagent, which causes agglutination (clumping) if antibodies are present, indicating a positive result.