PB2447 RED CELL ALLOIMMMUNIZATION A RETROSPECTIVE SINGLE CENTRE EXPERIENCE IN AN AREA WITH A LOW INCIDENCE OF HAEMOGLOBINOPATHY:

Background: Alloimmunization to Red Blood Cell (RBC) antigens could become a growing issue owing to increasing transfusion programs and an ageing population. The clinical impact of RBC alloimmunization is likely underestimated. It has been recognized that alloimmunization may compromise the therapeutic effect of RBC transfusion. Alloimmunized patients have an increased risk of serious haemolytic transfusion reactions (HTRs) and may not receive adequate RBC transfusion support due to lack of compatible RBC units. Since recently, alloimmunization is not routinely reported to SHOT and there is comparatively little data of its impact on clinical practice. Aims: Identifying transfusion‐related risk factors of alloimmunization against RBC antigens and correlate alloimmunization to the clinical data. Methods: A retrospective cohort study of all RBC‐alloimmunization in a district hospital (UKAS accredited laboratory) between January 2005 and January 2015. The demographics of the patients with alloantibodies, their medical history, and the transfusion‐related adverse events were examined to explore the concept of RBC alloimmunization itself may contribute to morbidity and mortality. Patients with haemoglobinopathies and palliative leukaemia's were excluded. Laboratory data included patients’ ABO/Rh type, antibody screening results, direct antiglobulin test, and alloantibody and autoantibody specificities. Data concerning transfusion reactions were obtained from the hospitals’ transfusion records. The retrospective study was done to find the incidence and type of RBC alloantibodies and to identify factors such as frequency of transfusion, and their association with the development of clinical complications. Results: The study encompasses all the patient whose immunohematological tests were conducted at the Department of Transfusion Medicine Nine patients were identified over the ten year period. Two cases were excluded due to incomplete data. Of the seven patients that had sufficient data the mean blood component requirements were 4.8 (media 3.4‐ 6.3) whereas platelets (PLT) was 1.2 platelet units (range 2.1 – 3.4) respectively. The number of alloimmunized transfused patients in our centre is < 1% ‐ likely bellow than the 1% to 3% commonly quoted, taking into consideration the frequent occurrence of RBC antibody evanescence ‐. The most frequent antibody specificity was anti‐E, followed by Jkb ‐ Jka −Lua, −D, −C and anti‐Wra. Unsurprisingly, we identify alloimmunization was associated with higher numbers of transfused RBC units (3 vs 6; p = 0.001), as well as with longer time under transfusion (4.3 vs. 8.1 months; p = 0.017) as well as increased mortality, in the scenario of previous malignancy. Summary/Conclusion: The clinical course for each of the reported patients provides insight into the direct and indirect consequences of RBC alloimmunization, where patients experienced delayed HTRs or did not receive needed RBC transfusions. Future work examining the clinical impact of RBC alloimmunization should not only consider HTRs but should also address the potential consequences associated with difficulties in obtaining compatible blood.