The significance of a positive DAT in thalassemia patients.

The DAT is performed for the detection of antibody or complement on the surface of RBCs. Our institution previously performed DATs on all chronically transfused thalassemia patients before each transfusion episode to detect early alloimmunization. The medical records of all thalassemia patients treated at our institution from 2004 to 2007 were reviewed to determine the significance of the high rate of positive DATs (52.5% of 80 patients). The majority of IgG-reactive DATs were associated with a nonreactive eluate (65.4% of 286 eluates performed). A positive DAT was significantly associated with splenectomy (χ² = 15.4; p < 0.001), elevated IgG levels (χ² = 26.8; p < 0.001), HCV (χ² = 20.7; p < 0.001), and warm autoantibody (χ² = 5.87; p = 0.03). Multivariate analysis revealed that only HCV (OR, 5.0; p = 0.037) and elevated IgG levels (OR, 9.0; p = 0.001) were independently associated with a positive DAT. Alloimmunized thalassemic patients were more likely to have a positive DAT than nonalloimmunized patients, but this association was not significant (OR, 2.2; p = 0.11). A positive DAT did not correlate with decreased response to transfusion, RBC survival, hemolysis, or increased transfusion requirements. Only two cases of early alloimmunization were detected by DAT among 288 DAT-positive samples studied during 4 years. This study demonstrated that the routine performance of DATs on pretransfusion specimens in thalassemic patients has limited clinical utility, and the elimination of this test will improve turnaround time and decrease costs.