EVALUATION OF PRE-TRANSFUSION LEUKOCYTE COUNT AS A PREDICTOR OF ALLERGIC TRANSFUSION REACTIONS: A RETROSPECTIVE COHORT STUDY

Abstract

Background: Allergic transfusion reactions (ATRs) are common non-hemolytic adverse events following blood component transfusion. Although donor- and product-related mechanisms have been extensively investigated, recipient related inflammatory factors are less well characterised. This study evaluated pre-transfusion total leukocyte count (TLC) and absolute neutrophil count (ANC) among patients who developed ATRs. Methods: This retrospective cohort study included 34 patients who developed ATRs following blood component transfusion between January 2022 and March 2025. Pre-transfusion complete blood count parameters were reviewed, with emphasis on TLC and ANC. Patients were categorised into a leukocytosis group (n=23) and a non-leukocytosis group (n=11) using institutional haematological reference ranges (TLC >10,000/µL and ANC >7,000/µL as elevated values). TLC and ANC were compared between groups using the independent-samples t-test and Mann-Whitney U test. Underlying diagnoses were also stratified. Results: Of the 34 patients with ATRs, 23 (67.6%) were categorised in the leukocytosis group and 11 (32.4%) in the non leukocytosis group. Mean TLC was 18,277.8 ± 7,839.4/µL in the leukocytosis group compared with 6,607.5 ± 2,374.6/µL in the non-leukocytosis group. Mean ANC was 13,429.1 ± 6,353.1/µL and 4,025.5 ± 1,698.2/µL, respectively. Both TLC and ANC differed significantly between the groups (p<0.001). Diagnostic stratification showed that the leukocytosis group included a broader representation of malignancy, autoimmune, infectious, hepatic, surgical/trauma, and chronic medical conditions. Conclusion: Elevated pre-transfusion leukocyte and neutrophil counts were frequently observed among patients who experienced ATRs in this cohort. These findings generate a hypothesis that the recipient's pre-transfusion inflammatory state may be relevant to ATR susceptibility. However, because all included patients had already developed an ATR and grouping was based on leukocyte indices, the present study cannot establish leukocytosis as an independent predictor of ATR occurrence. Controlled studies including transfused patients without ATRs are required.