The Indirect Coombs Test (ICT), also known as the Indirect Antiglobulin Test (IAT), is a laboratory test used in blood banking and immunohematology to detect the presence of antibodies in a patient's serum that could potentially react with red blood cells (RBCs). This test is an important step in blood compatibility testing, especially in the context of blood transfusions and the prevention of hemolytic transfusion reactions.