Red Blood Cell Distribution Width and Mortality in Patients With ARDS

Red blood cell distribution width (RDW) is predictive of mortality in critically ill patients with acute respiratory distress syndrome (ARDS) with high prognostic power. This was among the results of a study presented at the American Thoracic Society (ATS) 2022 International Conference, held in San Francisco, California, May 13 to 18.

Recognizing that data on the predictive value of RDW among critically ill patients with ARDS remain scarce, the researchers sought to establish the prognostic value of RDW in these individuals. The current observational study included all adult patients with ARDS referred to a single referral center at Charité University Medicine in Berlin, Germany, between 2007 and 2019. Daily RDW values were obtained, and the predictive validity of RDW on mortality was evaluated statistically.

A total of 1037 critically ill patients who were admitted for ARDS were evaluated. Study results showed that elevated RDW values (ie, great than 14.5%) were reported among 96.3% of the participants. Maximum RDW values during intensive care unit (ICU) stay were significantly higher among individuals who did not survive (19.5% [range, 18.2% to 21.5%]) vs those who did survive (18.3% [range, 16.7% to 20.5%]; P <.001).

Maximum RDW values corresponded significantly with clinical ARDS severity, based on the Berlin definition, and were highest in those individuals with severe forms of ARDS. Per the Youden method, an RDW cutoff level of 19.1% was shown to best stratify risk and was significantly associated with the following: (1) longer duration of mechanical ventilation (281 hours [range, 108 to 569 hours] vs 520 hours [range, 262 to 942 hours]; P <.0001), (2) longer ICU stay (13 days [range, 5.5 to 22 days] vs 24 days; [range, 13 to 42 days]; P <.0001); and (3) higher ICU mortality (28.3% vs 50.9%; odds ratio [OR], 2.6; 95% CI, 2.01-3.35; P <.0001).

Extracorporeal gas exchange with extracorporeal membrane oxygenation (ECMO) was implemented significantly more often in patients with RDW values above this threshold (26.3% vs 57.8%; OR, 3.8; 95% CI, 2.95-4.99; P <.001). Per logistic regression analyses with multivariate adjustment, RDW was shown to be an independent risk factor for ICU mortality in patients with ARDS (OR, 1.15; 95% CI, 1.1-1.2; P <.001). Use of a 2-dimensional approach showed that time spent above or below an elevated RDW value was important, with longer time periods spent above an elevated RDW level stratifying risk groups better than did single RDW cutoff levels alone.

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