INTRODUCTION: The Pediatric Index of Mortality 2 (PIM2) is one of the most 
commonly used scoring systems to predict mortality in patients admitted to 
pediatric intensive care units (PICU) in Argentina. The objective of this study 
was to validate the PIM2 score in PICUs participating in the Quality of Care 
Program promoted by the Argentine Society of Intensive Care.
POPULATION AND METHODS: Multicenter, prospective, observational, cross-sectional 
study. All patients between 1 month and 16 years old admitted to participating 
PICUs between January 1st, 2009 and December 31st, 2009 were included. The 
discrimination and calibration of the PIM2 score were assessed in the entire 
population and in different subgroups (risk of mortality, age, diagnoses on 
admission).
RESULTS: Two thousand, eight hundred and thirty-two patients were included. PIM2 
predicted 246 deaths; however, 297 patients died (p < 0.01). The standardized 
mortality ratio was 1.20 (95% confidence interval [CI]: 1.01-1.43). The area 
under the ROC curve was 0.84 (95% CI: 0.82-0.86). Statistically significant 
differences were detected between the observed and the predicted mortality for 
the entire population and for the different risk intervals (χ2: 71.02, df: 8, p 
< 0.001). Statistically significant differences were also found between observed 
and predicted mortality in adolescent patients (37/22, p = 0.03) and in those 
hospitalized due to respiratory disease (105/81, p = 0.03).
CONCLUSIONS: The PIM2 score adequately discriminates survivors from 
non-survivors. However, it underscores the overall risk of death, especially in 
adolescent patients and those hospitalized due to respiratory disease. It is 
critical to take such differences into account when interpreting results.