Prevalence and risk factors of red blood cell alloimmunization among sickle cell disease patients in resource-limited countries: A systematic review and meta-analysis.
BACKGROUND: Sickle cell disease (SCD) is an inherited hemoglobinopathy characterized by hemoglobin S production, in which homozygous individuals (HbSS) develop a broad range of acute and chronic complications. While disease-modifying and curative therapies are increasingly available in high-income settings, red blood cell (RBC) transfusion remains the mainstay of treatment in resource-limited countries and is associated with high rates of alloimmunization. This systematic review and meta-analysis aimed to estimate the prevalence of alloimmunization and identify associated risk factors among patients with SCD living in resource-limited settings. METHODS: Africa Journals Online (AJOL), Embase, PubMed, Scopus, and Web of Science were searched for original studies published from inception to December 15, 2025. Only studies conducted in low- and lower-middle-income countries (LMICs) were included. Eligible studies evaluated the prevalence of alloimmunization in patients with SCD receiving RBC transfusions. A random-effects meta-analysis of proportions was performed to pool quantitative data, while qualitative findings were systematically summarized in tabular form. Statistical heterogeneity was assessed using the I² statistic and further explored using Baujat plots, leave-one-out analyses, and meta-regression. RESULTS: Our analysis included 27 studies conducted in Africa (n = 23) and Asia (n = 4), predominantly from lower-middle-income countries (n = 19) and mainly employing a cross-sectional design (n = 20), comprising 3128 previously transfused patients with SCD. The pooled prevalence of RBC alloimmunization was 8.76% (95% CI: 6.71-11.37%; I² = 75%). Higher alloimmunization rates were observed in West and North Africa, particularly in Côte d'Ivoire, Egypt, and Nigeria, whereas lower rates were reported in Asia and East Africa. The most frequently identified antibodies belonged to the Rh blood group system (n = 153), followed by the Kell system (n = 65). CONCLUSION: In resource-limited settings, RBC alloimmunization is a frequent and clinically significant complication in patients with SCD, contributing to increased morbidity and potential mortality. Targeted and economically viable antigen matching may reduce alloimmunization rates and improve transfusion safety in LMICs.