RESUMO
Mismatched red blood cell phenotypes between donors and recipients in multiple blood transfusions can result in the development of alloimmunization in recipients. We studied in this research the effect of alloantibodies on the increase of need of blood transfusion in major thalassemiacs. This is a descriptive study in which 2 groups of major thalassemiacs with more and less than 20 days of blood transfusion intervals [27 patients vs. 25] were evaluated for the presence and frequency of alloantibodies and related factors. We used t-test and t-student tables for evaluating the results. 55% of patients in the first group had developed alloantibodies and their annual transfused blood volume was more than those who were not immunized [p<0.005]. Male gender and initial blood transfusion in children under 3 years old were related to the absence of alloantibodies. 100% of patients in the second group were immunized, and those who received higher amounts of blood units annually [493 ml/kg and 508 ml/kg] were patients with more than two types of alloantibodies. Alloimmunization involved K [27.5%], N [12.5%], CW, s, Fy[b] [5%], C, S, E, e and M [2.5%] antigens. 100% of antibodies were of warm immunoglobulin type, and 16% both warm and cold. 17.3% of thalassemiacs were splenectomized and their need for transfused blood was less than unsplenectomized patients [p<0.005]. In most cases, annual blood transfusion in both groups was estimated to be much more than what was expected. We conclude that red blood cell matching, at least for Kell and Rh systems, is necessary to prevent alloimmunization in thalassemiacs. Hypersplenism and low quality of blood, that can increase the need for transfused blood, should be taken into consideration