Performance of PRISM (Pediatric Risk of Mortality) score and PIM (Pediatric Index of Mortality) score in a tertiary care pediatric ICU.

OBJECTIVE: To validate Pediatric Risk of Mortality (PRISM) and Pediatric Index of Mortality (PIM) score.

METHODS: All consecutive patients over a six month period were included in the study except patients with a PICU stay of less than 2 hours, those transferred to other PICUs, pediatric surgical cases, trauma patients and those dying within 24 hours of admission. The PRISM and PIM scores of all patients included in the study were computed and the outcome was noted in terms of survival or non-survival. Mortality discrimination was quantified by calculating the area under the receiver operating characteristic (ROC) curve. Hosmer and Lemeshow goodness-of-fit test was used to calibrate the scores.

RESULTS: Two hundred and thirty patients were enrolled with mean age of 40.6 months and male to female ratio of 1.2:1. There were 56 deaths (mortality rate 24.3%). The mortality in infants was higher (37.8 %) as compared to non-infants (16.2 %) (p = 0.011). The predicted deaths with PRISM score was 24.3%. The area under the ROC curve was 0.851 (95% CI 0.790-0.912). The Hosmer and Lemeshow goodness-of-fit test showed good calibration (p = 0.627, chi square = 1.75, degree of freedom = 3). The predicted deaths with the PIM score was 7.38%. The area under the ROC curve for PIM score was 0.838 (95 % CI 0.776-0.899). The Hosmer and Lemeshow goodness-of-fit showed a poor calibration for PIM score (p = 0.0281, chi-square = 10.866, degree of freedom = 4).

CONCLUSION: Both PRISM and PIM scores have a good discriminatory performance. The calibration with PRISM score is good but the PIM score displays poor calibration.