Red blood cell alloimmunization in myelodysplastic syndromes: Associations with sex, DAT‐positivity, and increased transfusion needs

Abstract Background Many patients with myelodysplastic syndromes (MDS) need repeated red blood cell transfusions which entails a risk of immunization and antibody formation. Associations between alloantibodies, autoantibodies and increased transfusion requirements have been reported, but their relationship remains unclear. In this study, we analyzed factors potentially associated with red blood cell alloimmunization, as well as changes in transfusion intensity and post‐transfusion hemoglobin increments. Methods In a retrospective cohort study, we linked Swedish MDS patients diagnosed between 2003 and 2017 to transfusion and immunohematology data. Potentially associated factors were analyzed using Cox proportional hazards regression. The transfusion rate after detected alloimmunization was analyzed using a fixed effects Poisson regression. Post‐transfusion hemoglobin increments before and after alloimmunization were compared using a mixed effects regression. Results Alloantibodies following MDS diagnosis were detected in 50 out of 429 patients (11.7%). Female sex and a positive direct antiglobulin test (DAT) were independently associated with alloimmunization, with hazard ratios of 2.02 (95% confidence interval [CI] 1.08–3.78) and 9.72 (95% CI, 5.31–17.74), respectively. The transfusion rate following alloimmunization was increased with an incidence rate ratio of 1.33 (95% CI, 0.98–1.80) and the post‐transfusion hemoglobin increment after alloimmunization was 1.40 g/L (95% CI, 0.52–2.28) lower per red blood cell unit ( p = .002) compared to before alloimmunization, in multivariable analyses. Discussion Alloimmunization against blood group antigens was associated with sex, DAT‐positivity, increased transfusion needs, and lower post‐transfusion hemoglobin increments. These findings warrant further investigation to evaluate the clinical significance of up‐front typing and prophylactic antigen matching in patients with MDS.