Red Blood Cell Distribution Width (RDW) as Predictor of the Clinical Course and Mortality in Patients With Acute Respiratory Distress Syndrome (ARDS): A Retrospective Study.

Background and Aims: Evidence on the prognostic value of red blood cell distribution width (RDW) in critically ill patients with acute respiratory distress syndrome (ARDS) is limited. This study evaluated RDW as a predictor of mortality in patients with ARDS. Methods: A retrospective study conducted at an ARDS referral center included 1037 adult ICU patients (2007-2019). RDW values at ICU admission and during ICU stay were evaluated for their ability to predict mortality using statistical analyses, including logistic regression, Cox regression, and receiver operating curve analysis, and further specified according to Youden's method. Results: In total, 1037 ICU patients with ARDS were included in the analysis. Non-survivors had significantly higher RDW on ICU admission than survivors (survivors' median RDW 15.4% [14.2; 17.0%] vs. non-survivors' median RDW 16.55% [15.2; 18.0%]; p < 0.0001). A cut-off RDW ≥ 16.4% at ICU admission effectively stratified risk and was associated with higher SAPS II and APACHE II scores, prolonged mechanical ventilation, longer ICU stay, and higher ICU mortality. Patients with RDW ≥ 16.4% had almost double the risk of ICU death compared to those with lower values (hazard ratio: 1.96; 95% CI: 1.61-2.40; p < 0.001). Median survival was significantly lower in patients with RDW ≥ 16.4% (27 vs. 72 days; log rank, p < 0.0001). RDW values corresponded to ARDS severity and reflected worse clinical outcomes. Conclusion: RDW at ICU admission predicts mortality and clinical course in ARDS patients. RDW may serve as a reliable marker of ARDS severity and mortality risk in the ICU.