BACKGROUND: Severity of illness is an important consideration in making the 
decision to transfuse as it is the sicker patient that often needs a red cell 
transfusion. Red blood cell (RBC) transfusions could potentially have direct 
effects and interact with presenting illness by contributing to pathologies such 
as multi-organ dysfunction and acute lung injury thus exerting a considerable 
impact on overall morbidity and mortality. In this study, we examine if 
transfusion is an independent predictor of mortality, or if outcomes are merely 
a result of the initial severity as predicted by Pediatric Risk of Mortality 
(PRISM) III, Pediatric Index of Mortality (PIM2), and day 1 Pediatric Logistic 
Organ Dysfunction (PELOD) scores.
METHODS: A single center retrospective study was conducted using data from a 
prospectively maintained transfusion database and center-specific data at our 
pediatric ICU between January 2009 and December 2012. Multivariate regression 
was used to control for the effects of clinical findings, therapy, and severity 
scores, with mortality as the dependent variable. Likelihood ratios and area 
under the curve were used to test the fidelity of severity scores by comparing 
transfused vs. non-transfused patients.
RESULTS: There were 4975 admissions that met entry criteria. In multivariate 
analysis, PRISM III scores and serum hemoglobin were significant predictors of 
transfusion (p < 0.05). Transfused and non-transfused subjects were distinctly 
disparate, so multivariate regression was used to control for differences. 
Severity scores, age, volume transfused, and vasoactive agents were 
significantly associated with mortality whereas hemoglobin was not. A 
substantial number of transfusions (45 %) occurred in the first 24 h, and 
patients transfused later (24-48 h) were more likely to die compared to this 
earlier time point. Likelihood ratio testing revealed statistically significant 
differences in severity scoring systems to predict mortality in transfused vs. 
non-transfused patients.
CONCLUSIONS: This study suggests that RBC transfusion is an important risk 
factor that is statistically independent of severity. The timing of transfusions 
that related strongest to mortality remained outside the purview of severity 
scoring, as these happened beyond the timing of data collection for most scoring 
systems.