Frequency and Risk Factors of Red Cell Alloimmunization in Transfused Patients with Sickle Cell Disease and Sickle Cell–β Thalassemia: A Three-Year Retrospective Study from a Tertiary Care Centre.

Abstract

Background: Red cell alloimmunization is a clinically significant complication of repeated transfusions in sickle haemoglobinopathies. Comparative data from eastern India remain limited.

Objectives: To determine the frequency of alloimmunization in transfused patients with sickle cell disease (SCD) and SCD with β-thalassemia, and to identify associated demographic and transfusion-related risk factors.

Materials and Methods: A retrospective observational study was conducted at KIMS, Bhubaneswar, from October 2022 to October 2025. A total of 148 patients (131 SCD, 17 SCD+β-thalassemia) with a clearly recorded indirect Coombs test (ICT) result were analysed. Demographic and transfusion data were retrieved from blood bank registers. Statistical analysis included chi-square, Fisher's exact, Mann-Whitney U tests, and binary logistic regression.

Results: The overall alloimmunization frequency was 12.2% (18/148). Rates were 11.5% in SCD and 17.6% in SCD+β-thalassemia (p = 0.437). Alloimmunization increased significantly with transfusion burden, from 2.3% after one transfusion to 31.6% beyond ten transfusions (χ² = 10.23, p = 0.017). On multivariable regression, age was the only independent predictor (OR = 1.045/year, 95% CI 1.008–1.085, p = 0.018).

Conclusion: Alloimmunization affects approximately one in eight transfused patients with sickle haemoglobinopathies at this centre. Transfusion burden and age are the principal determinants. Extended antigen phenotyping and prophylactic Rh/Kell matching are strongly recommended, particularly for patients anticipated to receive more than five lifetime transfusions.