The Impact of Extended Typing On Red Blood Cell Alloimmunization in Transfused Patients.

Background: Red blood cell (RBC) alloimmunization is still an actual problem in our transfusion practice. In 2011, in addition to the regular ABO/D blood group typing, phenotyping for Rh (C, c, E, e) and Kell antigens was introduced for blood donors and patients undergoing blood transfusion. Our aim was to evaluate the impact of the extended RBC typing and donor/recipient matching on the incidence of RBC alloimmunization.

Methods: A retrospective comparative study was conducted by reviewing RBC request records for about 36,000 patients transfused with RBC in the period from 2013 to 2015 in comparison to the similar study conducted on 47,000 transfused patients in the period from 2005 to 2008. Pre-transfusion serologic testing data were retrieved for analysis. Blood samples with positive antibody screening and positive cross-match were further subjected to antibody identification. All the tests were performed using column agglutination technique (CAT) with ID-cards and reagents from DiaMed in both studies.

Results: Irregular RBC alloantibodies were detected in 116 (0.32%) out of 36,000 transfused patients. Multiple transfusions (15.8 units/patient) were given to 450 patients from which 79 (17.5%) had RBC allontibodies. The incidence of RBC alloimmunisation in the rest of the 35,550 transfused patients from which 37 had RBC alloantibodies was 0.10%. A total of 117 alloantibodies were identified in 96 out of the 116 patients with irregular RBC antibodies. Their specificity was as fallows: anti-E (25.6%), -C (6.0%), -c (8.5%), -e (0.85%), -C (5.1%), -K (12.8%), -Fy (10.2%), -Fy (2.5%), -Jk (7.7%), -Jk (2.5%), -M (9.4%), -S (1.7%), -s (0.85%), -Lu (1.7%), -Le (3.4%) and anti-Le (0.85%). Multiple antibodies were identified in 22 of the transfused patients out of which 15 (68.2%) received multiple transfusions. Anti-E was the most common antibody found in more of the 50% of the multiple antibody cases.

Conclusions: The overall incidence of RBC alloimmunization in transfused patients decreased from 0.51% which was the estimated incidence for the period before the introduction of the extended RBC typing (2005-2008) to 0.32% (2013-2015). This is due to the decreased incidence of RBC alloimmunization in the multiply transfused patients from 33.9% to 17.5% respectively. The current frequency of anti-E (25.6%) and -K (12.8%) antibodies in transfused patients are significantly lower than their previous estimated frequencies of 30.4% and 24.0% respectively, as well as the overall frequency of RBC antibodies to Rh+Kell antigens which decreased from 72.4% to 53.8%. Extended donor-recipient matching for C, c, E, e and Kell antigens has proved a beneficial effect on the incidence of RBC alloimmunization in multiply transfused patients.