Red blood cell processing methods and in-hospital mortality: a transfusion registry cohort study

BACKGROUND: Quality of red blood cells (RBCs) varies depending on the method of processing the whole blood donation, and the method of processing might affect outcomes in patients transfused RBCs. We aimed to establish whether an association exists between in-hospital mortality and RBC processing method and duration of storage. METHODS: We did a retrospective registry cohort study using data from three acute care hospitals in Hamilton, ON, Canada, and Canadian Blood Services over a 6-year period (2008-14). Adult patients (≥18 years) who were admitted to hospital and who received RBC transfusions were included in the study. All transfused RBCs were characterised by the method of processing (red cell filtered or whole blood filtered) and storage age (fresh 1-7 days, mid 8-35 days, and old 36-42 days). The primary outcome was in-hospital mortality. We used Cox proportional hazards regression with time-dependent stratification variables and fixed stratification variables, and controlled for patient covariates. FINDINGS: Between April 1, 2008, and March 31, 2014, 91 065 RBC transfusions were given to 23 634 adults who were included in the analyses. When storage duration was included in the model, in-hospital mortality was significantly increased with fresh whole blood filtered units compared with the reference group of mid-age red cell filtered units (hazard ratio 2·19, 95% CI 1·09-4·42; p=0·033). Differences between other age and processing categories were not significant. INTERPRETATION: The potential effect of whole blood processing methods on patient outcomes is worthy of further investigation, since adverse outcomes could be reduced by minor changes to blood processing methods and inventory management policies. FUNDING: Canadian Blood Services, Health Canada, and the Canadian Institutes of Health Research.