The prognostic role of red blood cell distribution width in transfused and non-transfused critically ill patients.

Background: Red blood cell distribution width (RDW) value is gaining popularity as a prognostic factor in critically ill patients. However, its role in transfused patients is unclear. The aim of this study was to evaluate the predictive value of Red blood cell distribution width (RDW) on Intensive Care Unit (ICU) admission for 90-day mortality among either transfused or non-transfused critically ill patients.

Methods: This observational cohort study includes 286 patients with at least 48 hours of ICU length of stay. Patients were analyzed separately in two groups, depending on whether or not they were transfused in the last 72 hours before ICU admission.

Results: One hundred seventeen (117) patients (41%) were transfused. Patients with high RDW on admission (N.=181, 63%) had higher 90-day mortality both in non-transfused (26/87, 30% vs. 12/82, 14% P=0.03) or transfused (39/94, 41% vs. 2/23, 8% P=0.003) patients. The area under the curve of admission RDW values to predict 90-day mortality was 0.660 and 0.610 for non-transfused and transfused patients, respectively. The Youden Index analysis showed that an RDW value of 14.3% was the best cut-off to predict mortality in the non-transfused group, while 15.3% was the best cut-off in the transfused group.

Conclusions: High RDW values on ICU admission are independently associated with 90-day mortality in critically ill patients regardless of previous red blood cells transfusion. However, we identified two different cut-offs of "high RDW" to be used in ICU in transfused and non-transfused patients.