Prevalence and risk factors for red blood cell alloimmunization in 175 children with sickle cell disease in a French university hospital reference centre

Patients with sickle cell disease (SCD) show a high prevalence of red blood cell (RBC) alloimmunization, but few studies have focused on children. We aimed to study the prevalence and risk factors of RBC alloimmunization in SCD children. We retrospectively analysed the medical and transfusion files for 245 SCD children hospitalized in our centre in 2014 and included 175 patients who had received at least one RBC unit in their lifetime. The main clinical and immuno-haematological characteristics of alloimmunized and non-alloimmunized patients were compared. The prevalence of alloimmunization was 13.7% [95% confidence interval (CI) (8.6-18.6)], and 7.4% [95% CI (3.5-11.3)] after excluding the probable irregular natural antibodies (anti-M, anti-Le(a), anti-Le(b), anti-Le(x)). Main risk factors for alloimmunization were increased number of RBC units received (median of 65 vs. 10 units per patient; P - 0.01) and the presence of one or more red cell autoantibodies (46.2% vs. 4.7%; P < 0.0001). The alloimmunization rate was higher for episodically transfused than chronically transfused patients (1.43 vs. 0.24/100 units received; P < 0.001). The presence of red cell autoantibodies appears to be a major risk factor for alloimmunization in SCD children and could justify specific transfusion guidelines.