Elevated red blood cell distribution width at ICU discharge is associated with readmission to the intensive care unit

Background: Red blood cell distribution width (RDW) is a predictor of mortality in critically ill patients. Our objective was to investigate the association between the RDW at ICU discharge and the risk of ICU readmission or unexpected death in the ward. Methods: A secondary analysis of prospectively collected data study was conducted including patients discharged alive from the ICU to the ward. The target variable was the RDW collected at ICU discharge. Elevated RDW was defined as an RDW > 16%. Outcomes of interest included readmission to the ICU, unexpected death in the ward and in-hospital death. Variables with a p-value < 0.1 in the univariate analysis or with biological plausibility for the occurrence of the outcome were included in the Cox proportional hazards model for adjustment. Results: We included 813 patients. A total of 138 readmissions to the ICU and 44 unexpected deaths in the ward occurred. Elevated RDW at ICU discharge was independently associated with readmission to the ICU or unexpected death in the ward after multivariable adjustment (HR: 1.901; 95% CI 1.357-2.662). Other variables associated with this outcome included age, tracheostomy and mean corpuscular volume (MCV) at ICU discharge. Similar results were obtained after the exclusion of unexpected deaths in the ward (HR 1.940; CI 1.312-2.871) and for in-hospital deaths (HR 1.716; 95% CI 1.141-2.580). Conclusions: Elevated RDW at ICU discharge is independently associated with ICU readmission and in-hospital death.