To the Editor.
—I agree with Dr Pollack and his colleagues'1 major finding that variations in mortality rates in pediatric intensive care units (ICUs) may be partially explained by variables such as presence of a pediatric intensivist and teaching hospital status. However, I do not agree with the authors' post hoc analysis, which suggests that care by pediatric residents is associated with increased mortality. The authors fail to point out alternative explanations for their analysis, and their data are not entirely consistent with their conclusions.The authors found that teaching hospital status was significantly associated with increased mortality rates, even after adjusting for case mix severity. It is not surprising that the presence of pediatric residents was also a predictor of mortality since they are highly correlated variables (teaching hospitals are the primary sites for training pediatric residents). The authors' statistical model found that the presence of pediatric residents