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RBC Distribution Width: Biomarker for Red Cell Dysfunction and Critical Illness Outcome?
Ahmed S Said1, Philip C Spinella, Mary E Hartman
11Department of Pediatrics, Washington University in St. Louis, St. Louis, MO. 2Department of Pathology and Immunology, Washington University in St. Louis, St. Louis, MO. 3Department of Biostatistics, Washington University in St. Louis, St. Louis, MO. 4Department of Biochemistry & Molecular Biophysics, Washington University in St. Louis, St. Louis, MO. 5Department of Pediatrics, University of Utah, Salt Lake City, UT.
Insights
Red blood cell distribution width (RDW) predicts outcomes in critically ill children. Higher RDW and its change are linked to increased ICU mortality or ECMO use, suggesting it may indicate red blood cell injury.
Area of Science:
- Pediatric critical care medicine
- Hematology
- Clinical pathology
Background:
- Red blood cell distribution width (RDW) is an established predictor of outcomes in various adult conditions.
- Its association with morbidity and mortality in critically ill children remains less understood.
Purpose of the Study:
- To investigate the association between RDW and outcomes in critically ill children.
- To determine if RDW is an independent predictor of mortality or morbidity in this population.
Main Methods:
- Retrospective observational study of 3,913 children admitted to a tertiary PICU.
- Collected data included demographics, laboratory values, hospitalization characteristics, and outcomes.
- Calculated admission RDW and the relative change in RDW within the first 7 days of hospitalization.
Main Results:
- Both admission RDW and its relative change were independently associated with ICU mortality or extracorporeal membrane oxygenation (ECMO) use.
- Odds ratios for mortality/ECMO were 1.13 for admission RDW and 1.04 for RDW change, after adjusting for illness severity.
- Both RDW measures weakly correlated with fewer ICU- and ventilator-free days.
Conclusions:
- Admission RDW is independently associated with ICU mortality and morbidity in critically ill children.
- RDW may serve as a biomarker for red blood cell injury impacting critical illness outcomes, potentially through impaired oxygen delivery.
- These findings highlight RDW's potential clinical utility in pediatric critical care.
Objectives:
RBC distribution width is reported to be an independent predictor of outcome in adults with a variety of conditions. We sought to determine if RBC distribution width is associated with morbidity or mortality in critically ill children.
Design:
Retrospective observational study.
Setting:
Tertiary PICU.
Patients:
All admissions to St. Louis Children's Hospital PICU between January 1, 2005, and December 31, 2012.
Interventions:
We collected demographics, laboratory values, hospitalization characteristics, and outcomes. We calculated the relative change in RBC distribution width from admission RBC distribution width to the highest RBC distribution width during the first 7 days of hospitalization. Our primary outcome was ICU mortality or use of extracorporeal membrane oxygenation as a composite. Secondary outcomes were ICU- and ventilator-free days.
Measurements And Main Results:
We identified 3,913 eligible subjects with an estimated mortality (by Pediatric Index of Mortality 2) of 2.94% ± 9.25% and an actual ICU mortality of 2.91%. For the study cohort, admission RBC distribution width was 14.12% ± 1.89% and relative change in RBC distribution width was 2.63% ± 6.23%. On univariate analysis, both admission RBC distribution width and relative change in RBC distribution width correlated with mortality or the use of extracorporeal membrane oxygenation (odds ratio, 1.19 [95% CI, 1.12-1.27] and odds ratio, 1.06 [95% CI, 1.04-1.08], respectively; p < 0.001). After adjusting for confounding variables, including severity of illness, both admission RBC distribution width (odds ratio, 1.13; 95% CI, 1.03-1.24) and relative change in RBC distribution width (odds ratio, 1.04; 95% CI, 1.01-1.07) remained independently associated with ICU mortality or the use of extracorporeal membrane oxygenation. Admission RBC distribution width and relative change in RBC distribution width both weakly correlated with fewer ICU- (r = 0.038) and ventilator-free days (r = 0.05) (p < 0.001).
Conclusions:
Independent of illness severity in critically ill children, admission RBC distribution width is associated with ICU mortality and morbidity. These data suggest that RBC distribution width may be a biomarker for RBC injury that is of sufficient magnitude to influence critical illness outcome, possibly via oxygen delivery impairment.
