Tehran University of Medical Sciences International Journal of Hematology-Oncology and Stem Cell Research 2008-2207 17 1 2023 01 16 4 8 Farzad Mollahoseini Foomani Blood Transfusion Organization Research Center, Iranian Blood Transfusion Organization, Mashhad, Iran Mahammad Hadi Sadeghain Cancer Molecular Pathology Research Center, Mashhad University of Medical Sciences, Mashhad, Iran Saeede Bagheri Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran Zahra Badiee Pediatrics Department, Doctor Sheikh Hospital, Mashhad University of Medical Sciences, Mashhad, Iran Reihane Bazargani Blood Transfusion Organization Research Center, Iranian Blood Transfusion Organization, Mashhad, Iran Zahra Aryanpour Blood Transfusion Organization Research Center, Iranian Blood Transfusion Organization, Mashhad, Iran Saeid Hallajian Blood Transfusion Organization Research Center, Iranian Blood Transfusion Organization, Mashhad, Iran Seyyede Fatemeh Shams Blood Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran 2020 10 31 2021 05 01 Background:  Thalassemia is an inherited disease with anemia and hemolysis. Blood transfusion is a routine treatment for thalassemia patients; alloimmunization is one of the complications of blood transfusion, which is very serious for these patients, especially girls and young women.    Materials and Methods:  Four hundred forty-six thalassemia patients were examined in this cross-sectional study. Demographic information of patients was extracted and recorded. The phenotype of ABO, Rh, and Kell antigens (tube method) with antisera from IMMUNDIANOSTICA Company (Germany) and the frequency of alloantibodies were determined. Results: 55.8% of the studied individuals were male and 44.2% were female. The mean age of the studied patients was 19.94±10.63.  The alloantibodies were detected in 7.5% of pack cell receivers. The most prevalent phenotype of the ABO system was the O blood group (37.4%), and the most abundant antigen of the Rh group was ‘e’, which was found in 99.8% of the studied population. The most frequently detected alloantibody was Anti K (38.2%); concerning kell phenotype, (K_k+) and (K+k+) were found in 99.3% and 0.7% of patients, respectively. The frequency of Anti-D, Anti-C, Anti-c, and Anti-E was 23.5%, 14.7%, 2.9%, and 14.7%, respectively. Conclusion: According to the results of this paper, finding the compatible pack cells in terms of Kell and Rh systems antigens in addition to the ABO blood group is recommended to decrease the rate of alloantibodies in thalassemia patients. https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/view/1453 https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/download/1453/957