Antibody screening in 37 degrees C saline. Is it safe to omit it using the indirect antiglobulin (gel) test?

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 degrees 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 degrees 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 degrees C saline and by IAT using the DiaMed gel system. The screening tests were performed using 50 microL of 0.8% low-ionic-strength saline suspended RBCs and 50 microL of plasma. The tests were examined for agglutination and hemolysis. Two hundred and thirty three samples (9.81%) were reactive by IAT and 88 (3.70%) by 37 degrees C saline. All 88 samples reactive by 37 degrees C saline also reacted by IAT. These data indicate that 37 degrees C saline is not an essential pretransfusion procedure when the DiaMed gel test is used.