title: Red Blood Cell Distribution Width as a Pragmatic Marker for Outcome in Pediatric Critical Illness.
abstract: BACKGROUND
  Red cell distribution width (RDW) is a routine laboratory measure associated with poor outcomes in adult critical illness.
  
  
  OBJECTIVE
  We determined the utility of RDW as an early pragmatic biomarker for outcome in pediatric critical illness.
  
  
  METHODS
  We used multivariable logistic regression to test the association of RDW on the first day of pediatric intensive care unit (PICU) admission with prolonged PICU length of stay (LOS) >48 hours and mortality. The area under the receiver operating characteristic curve (AUROC) for RDW was compared to the Pediatric Index of Mortality (PIM)-2 score.
  
  
  RESULTS
  Over a 13-month period, 596 unique patients had RDW measured on the first day of PICU admission. Sepsis was an effect modifier for LOS >48 hours but not mortality. In sepsis, RDW was not associated with LOS >48 hours. For patients without sepsis, each 1% increase in RDW was associated with 1.17 (95% CI 1.06, 1.30) increased odds of LOS >48 hours. In all patients, RDW was independently associated with PICU mortality (OR 1.25, 95% CI 1.09, 1.43). The AUROC for RDW to predict LOS >48 hours and mortality was 0.61 (95% CI 0.56, 0.66) and 0.65 (95% CI 0.55, 0.75), respectively. Although the AUROC for mortality was comparable to PIM-2 (0.75, 95% CI 0.66, 0.83; p = 0.18), RDW did not increase the discriminative utility when added to PIM-2. Despite the moderate AUROC, RDW <13.4% (upper limit of lower quartile) had 53% risk of LOS >48 hours and 3.3% risk of mortality compared to patients with an RDW >15.7% (lower limit of upper quartile) who had 78% risk of LOS >48 hours and 12.9% risk of mortality (p<0.001 for both outcomes).
  
  
  CONCLUSIONS
  Elevated RDW was associated with outcome in pediatric critical illness and provided similar prognostic information as the more complex PIM-2 severity of illness score. Distinct RDW thresholds best discriminate low- versus high-risk patients.
authors.affiliation: Division of Critical Care Medicine, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States of America.
authors.forename: Alexis L
authors.initials: AL
authors.lastname: Ramby
authors.affiliation: Division of Critical Care, Department of Pediatrics, Ann & Robert H. Lurie Children's Hospital of Chicago, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America.
authors.forename: Denise M
authors.initials: DM
authors.lastname: Goodman
authors.affiliation: Division of Critical Care, Department of Pediatrics, Ann & Robert H. Lurie Children's Hospital of Chicago, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America.
authors.forename: Eric L
authors.initials: EL
authors.lastname: Wald
authors.affiliation: Division of Critical Care, Department of Anesthesia and Critical Care Medicine, The Children's Hospital of Philadelphia, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States of America.
authors.forename: Scott L
authors.initials: SL
authors.lastname: Weiss
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D016638:Critical Illness / Q000401:mortality*; D004909:Erythrocyte Indices / Q000502:physiology*; D004912:Erythrocytes / Q000502:physiology*; D005260:Female; D017052:Hospital Mortality; D006760:Hospitalization; D006801:Humans; D007223:Infant; D015278:Intensive Care Units, Pediatric; D007902:Length of Stay; D016015:Logistic Models; D008297:Male; D011379:Prognosis; D012372:ROC Curve; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D012772:Shock, Septic / Q000401:mortality* / Q000473:pathology*
chemical_list: D015415:Biomarkers