Prevention of allergic transfusion reactions to platelets and red blood cells through plasma reduction

BACKGROUND: The incidence of allergic transfusion reactions (ATRs) ranges from 1% to 3% of all transfusions, and they are difficult to prevent. This study evaluated whether removing plasma from apheresis platelets (APs) or red blood cells (RBCs) by concentrating or washing transfusion products can decrease the incidence of ATRs. STUDY DESIGN AND METHODS: A retrospective cohort study of 179 individuals who received unmanipulated and subsequently concentrated and/or washed APs was conducted. Poisson regression with generalized estimating equations was used to estimate the incident rate ratios and 95% confidence intervals (CIs) of ATRs. RESULTS: The incidence of ATRs to unmanipulated APs was 5.5% (306 ATRs/5575 AP units). The incidence decreased to 1.7% (135 ATRs/4327 AP units) when individuals received concentrated APs (73% reduction; 95% CI, 65%-79%) and 0.5% (21 ATRs/4082 AP units) when individuals received washed APs (95% reduction; 95% CI, 91%-97%). Of the 39 individuals who received unmanipulated RBCs and subsequently washed RBCs, the incidence of ATRs decreased from 2.7% (33 ATRs/1236 RBC units) to 0.3% (2 ATRs/733 RBC units; 89.4% reduction; 95% CI, 55.5%-97.5%). The median number of AP transfusions to first ATR was six (interquartile range [IQR], 2-19) for unmanipulated APs and increased to 13 (IQR, 4-32) for concentrated APs and 40 (IQR, 29-73.5) for washed APs. CONCLUSIONS: Concentrating APs and washing APs and RBCs substantially reduces ATRs, suggesting that the plasma component of APs and RBCs has an essential role in the etiology of ATRs.