Pediatric Index Mortality 3 (PIM3) Score as a predictor of mortality in pediatric care unit located at high altitude

The Pediatric Index of Mortality 3 (PIM3) is a scale that estimates the risk of mortality in children admitted to the Pediatric Intensive Care Unit (PICU) within the first hour of admission. Objective: to validate the PIM3 scale in pediatric population admitted to PICU at altitudes over 2,500 meters above sea level (m.a.s.l.), and to evaluate whether lactate and the oxygen saturation/fraction of inspired oxygen (SpO2/FiO2) index improve its ability to predict mortality. Patients and Method: A prospective multicenter study was carried out in 10 PICUs in Colombia between November 2016 and June 2017. Variables were collected for the calculation of PIM3, serum lactate, and SpO2/FiO2 index. Their discrimination capacity was validated with the area under the ROC curve and calibration using the Hosmer Lemeshow goodness-of-fit test. Results: 2,803 admissions were included, with an overall mortality of 4.8% and a standardized mortality ratio of 1.1 (95%CI 1.00-1.3). PIM3 showed low calibration (p < 0.001) and adequate discrimination for the studied population (ROC 0.84; 95%CI 0.83-0.86). The addition of serum lactate and SpO2/FiO2 allowed a good calibration (p = 0.75) and maintained a high discrimination of mortality (ROC 0.86; 95%CI 0.84-0.87). Conclusions: The performance of the PIM3 scale has adequate discrimination, but low calibration in children admitted to PICU at above 2500 m. a. s. l. Lactate and SpO2/FiO2 variables improved its predictive ability.