Prevalence and clinical significances of red cell alloimmunization and red cell bound immunoglobulin G in polytransfused patients with thalassemias.

The study was to determine the prevalence and clinical significances of red blood cell (RBC)-bound IgG as detected by flow cytometry in polytransfused patients with thalassemias. Relationship of the presence of RBC-bound IgG with RBC alloimmunization was also evaluated. This study included 59 polytransfused patients with β-thalassemia disease. We studied the frequency of RBC autoantibodies and alloimmunization. Direct Coombs test and flow cytometry were performed to detect the presence of RBC autoantibodies while RBC alloantibodies were detected by antibody screening and identification assays. Eight (13.6%) and 34 (57.6%) patients were found a positive direct Coombs test and flow cytometry, respectively. Twenty (33.9%) patients developed RBC alloantibodies. The four most frequent RBC alloantibodies were anti-E (55%), anti-Mia (40%), anti-Di(a) (25%) and anti-c (15%), respectively. There was no significant difference in the presence of RBC-bound IgG between polytransfused with thalassemia patients who developed RBC alloimmunization (13 of 20; 65%) and those without RBC alloantibodies (21 of 39; 53.8%), p = 0.412. Splenectomy and increased transfusion requirement were significantly associated with the presence of RBC-bound IgG but not with RBC alloantibody formation. The overall frequency of RBC alloantibody formation in polytransfused patients with thalassemias was 33.9%. The most common RBC alloantibody was anti-E. RBC autoantibody formation was more frequently detected by flow cytometry (57.6%) than by direct Coombs test (13.6%). Splenectomy was significantly associated with the development of autoreactive RBC-bound IgG antibodies in the polytransfused patients with thalassemias. The presence of the anti-RBC autoantibodies may cause an increase of transfusion requirement.