Direct antiglobulin test positivity in multi-transfused thalassemics

Red cell allo- and auto-immunization is a well recognized problem in multi-transfused thalassemic patients. We conducted this study on 301 multi-transfused thalassemic patients under the Thalassemia Transfusion Programme of Advanced Pediatric Centre of PGIMER.

The study was designed to determine the frequency of alloimmunization and autoimmunization in multi-transfused thalassemic patients and to establish the specificity of alloantibody to red cell antigens, if alloimmunization is detected.

The antibody screening was performed by the conventional tube technique using commercially available three cell screening panel (Diamed Switzerland) by saline, low ionic strength solution (LISS) and albumin indirect antiglobulin test (IAT). Samples with alloantibodies were then tested with red cell identification panel to determine the alloantibody specificity. Autoantibody screening was performed by direct antiglobulin test (DAT) during pre-transfusion testing.

Of the 301 patients, 52 (17.28%) were found to have antibodies (-allo and -autoantibodies). A total of 11 red cell alloantibodies were detected in 10 patients and the specificities were anti-Kell in 6(54.5%), anti-D in 2(18.2%), anti-c in 1(9.1%) and a combination of anti-E (9.1%) and anti-Jk(b) in 1 (9.1%) patients. DAT was positive in 48 (15.9%) patients. The frequency of autoantibody was significantly higher in alloimmunized group as compared to non-alloimmunized group (60% V/s 14.4%). Also, the pre-transfusion hemoglobin was significantly lower in the immunized group (8.5 gm/dl V/s 9.0 gm/dl; p=0.03) than the non-immunized group.

Based on these observations, we suggest antigen typing of all thalassemia major patients for ABO, Rh and Kell antigens before initiating transfusion therapy. Also, screening for allo- and auto-antibodies at regular intervals should be done prior to each transfusion.