Trends of red cell alloimmunization in β thalassemia major patients: A single center retrospective study in Karachi

This open-access article is distributed under the terms of the Creative Commons Attribution Non-Commercial License (CC BY-NC) (http:// creativecommons.org/licenses/by-nc/4.0/), which permits reuse, distribution and reproduction of the article, provided that the original work is properly cited and the reuse is restricted to noncommercial purposes. For commercial reuse, contact [email protected] T thalassemia syndrome is a heterogeneous group of inherited disorders caused by genetic lesions leading to decrease synthesis of one or more of the globin subunit (1). Thalassemia occurs with high frequency in a broad belt extending from the Mediterranean basin through the Middle East (Iran), India and Southeast Asia (2,3). Major complications related to frequent blood transfusions in β thalassemia major includes iron overload, multi organ damage and alloimmunization to erythrocyte antigens (1,4-8). Alloimmunization is a transfusion complication which may occur in immunocompetent transfusion dependent recipients. Blood is matched routinely only with respect to ABO antigens as well as D antigen which is the most important member of the Rh blood group system. Therefore, there is a probability that a donor may have that red cell antigen not present in the recipient, this disparity of blood group system can lead to alloimmunization (4,5,9-12). The etiology of alloimmunization has multiple origins and comprises primarily of three contributing factors including antigenic variations of red blood cells and differences between donor’s and the recipient’s blood, immune status of the recipient and the immunomodulatory effect of the allogenic blood transfusions on the recipient’s immune system (1,4,5,7,11). Alloimmunization is a serious and unfortunate complication that causes difficulty in obtaining compatible blood, delayed transfusion reactions and even occasional life-threatening events (5-8,12). The frequency of alloimmunization to red cell antigens in thalassemia major patients has varied from 5-30% (4,9). Previous research shows that the late start of blood transfusion and irregular frequency increases the incidence of alloimmunization in β Thalassemia patients (8,11,13). Early and regular blood transfusion therapy in thalassemia patients decreases the complication of severe anemia and enhances duration of survival (8,11,13). Alloimmunization is often a less significant problem among patients where transfusion was initiated before the age of 3; however, it has also been reported that alloimmunization is reduced if transfusion is commenced before the age of 5 (5,11,13). There is a high frequency of alloimmunization in splenectomised beta thalassemia patients reported in literature. The nonfunctional spleen or absence of spleen in patients with beta thalassemia causes augmentation of immune response against transfused foreign antigens (5). In transfusion dependent thalassemia patient, frequency of red cell autoantibodies is less than the rate of alloimmunization (6-8). Consequences of auto antibodies include difficulties in finding compatible blood, cross matching and because of more transfusion reactions possibility of life threatening reactions (6-8). Thalassemia is most common amongst inherited haemoglobin disorders in Pakistan becoming one of the major public health problems (14-16). The issue is compounded through limited availability of data on the incidence of RBC alloimmunization in transfusion-dependent thalassemia patients in Pakistan. In the present retrospective study we analyze the frequency of alloimmunization in thalassemia patients and evaluation of factors responsible in the occurrence of such complications.