Pretransfusion tests must detect antibodies that can shorten the life of red blood cells (RBCs). Some studies have demonstrated the existence of clinically significant antibodies detected at 37°C in saline that are not detected by the indirect antiglobulin test (IAT) when the conventional tube test is used. Our aim was to determine whether these antibodies, detected with a 37°C saline tube test, are also detected when a sensitive column gel agglutination method is used. The 2373 pretransfusion samples were tested as they were received (from May 1998 to December 1999), in 37°C saline and by IAT using the DiaMed gel system. The screening tests were performed using 50