Abstract
Background and Objectives
Alloimmunization is the most serious problem in thalassemia patients and Anti-K is the most prevalent antibody in these patients. So accurate identification of this antigen can significantly decrease the rate of alloimmunization. Serological phenotyping is usually not reliable in multi-transfused patients. Molecular genotyping can overcome limitations of hemagglutination assays, resolve discrepant serologic typing and guide RBC selection for them. In this regard, we intended to determine the K and k among alloimmunized thalassemia patients using molecular methods and compare the results between different methods. 
 
Materials and Methods
In this descriptive study, a total of 200 blood samples were collected randomly from alloimmunized thalassemia patients of Tehran Adult Thalassemia Clinic. The phenotype of all samples was determined for K and k. PCR-SSP was performed for all samples. The discrepant results between the phenotype and genotype were re-evaluated by PCR-RFLP and were confirmed by DNA sequencing.
 
Results
Sixty-three (28%) out of 200 patients developed Anti-K. Molecular typing of samples for K and k antigens revealed 96% (192 patients) KEL*02/KEL*02 and 4% (8 patients) KEL*01/KEL*02 among our samples. Discrepancy between the serology and genotyping results were detected in 8 cases that in all cases correction of genotype results was confirmed by DNA sequencing.
 
Conclusions 
This study demonstrates that antibodies against K antigen continue to develop in thalassemia patients at high rate. Our findings suggest that RBC molecular genotyping is superior to serological phenotyping and is a good alternative and more reliable method especially in multi transfusion patients such as thalassemia patients.