Delayed hemolytic transfusion reactions. An often-missed entity.

Delayed hemolytic transfusion reactions in eight persons were manifested solely or primarily by an apparently unexplained posttransfusion decrease in the hematocrit value. Alloantibodies were eventually found in all eight patients, but were sometimes undetectable for as long as 72 hours after the reaction. This did not preclude the occurrence of a new, acute hemolytic reaction. There were three instances of reversible renal failure complicating the reaction. In two patients, some or all of the antibodies became undetectable after four and nine months. In a third, the indirect antiglobulin reactions became considerably weaker after 12 months. Patients previously sensitized to RBC antigens should have available records inspected and a warning device (wristband or wallet card) provided to help prevent reactions caused by an anamnestic antibody rise.