Determination of need for elution studies for positive direct antiglobulin tests in pretransfusion testing.

Retrospective evaluation of elution studies for specimens with positive direct antiglobulin test (DAT) results during a three-month interval revealed 29 warm autoantibodies and 28 nonreactive eluates. Clearly, routine elution studies were nonproductive. However, there was no evaluation method for exclusion from elution studies. Therefore, an algorithm correlating laboratory, transfusion, and clinical data was developed. It identified delayed hemolytic transfusion reactions and possible autoimmune hemolytic anemia. By following the algorithm, technologists would perform elution studies, forego them, or consult the Medical Director. To test the algorithm, 568 positive DATs identified from 12,416 specimens were analyzed. Technologist evaluation without medical consultation for 194 specimens yielded 106 elution studies; 374 specimens required medical consultation, and 166 had eluates. Seven delayed hemolytic transfusion reactions were found. This suggests certain elution studies can be eliminated routinely. However, DATs with positive results associated with possible delayed hemolytic transfusion reactions require investigation. The search for autoimmune hemolytic anemia was not productive.