Evaluation of a positive autologous control in pretransfusion testing.

The clinical usefulness of autologous control (AC) in pretransfusion testing was evaluated. The records of 515 blood samples with positive direct antiglobulin tests detected by positive AC were reviewed. This represents 3.5% of 14,548 pretransfusion samples tested during a one-year period. One hundred ninety-four of 515 samples required further elution studies, and the results were 114 nonreactive, 18 autoantibodies, 52 ABO isoagglutinins, 5 transfusion-induced alloantibodies, and 5 unidentifiable antibodies. All alloantibodies also were detected in the serum. Therefore, AC and the elution results provided no further information in selecting blood for compatibility testing. By reviewing the patients' records, the authors determined that, only in five cases, the report of positive AC and elution results changed diagnosis or therapeutic course. The information of positive AC rarely was used in either assuring compatibility of blood or management of the patients clinically.