Scoring systems in pediatric intensive care: PRISM III versus PIM

Objective: To compare the performance of two different clinical scoring systems that were developed to assess mortality probability in pediatric intensive care, Design and methods: Prospective cohort study in a multidisciplinary tertiary pediatric intensive care unit. The Pediatric Risk of Mortality score (PRISM III) and the Pediatric Index of Mortality (PIM) were collected for each patient. Standardized mortality rate (SMR), discrimination and calibration of both scoring systems were compared by goodness-of-fit tests and receiver operating characteristic (ROC) curves. Results: Data from 303 patients were collected over a 9-month period. Twenty patients (6.6%) died in the PICU. Expected mortality based on PRISM III (12 h) was 6.96% (SMR 0.95; 95% CI 0.68-1.23), based on PRISM III (24 h) was 6.95% (SMR 0.95; 0.67-1.22) and based on PIM was 7.5% (SMR 0.88; 0.55-1.20). Calibration by Hosmer-Lemeshow goodness-of-fit test showed for PRISM III (12 h) chi(2) (8)=10.8, p=0.21; for PRISM III (24 h) chi(2) (8)=13.3, p=0.21 and for the PIM score chi(2) (8)=4.92, p=0.77. Discriminatory performance assessed by ROC Curves showed an area under the curve of 0.78 (95% CI 0.67-0.89) for the PRISM III score both after 12 and 24 h and 0.74 (0.63-0.85) for the PIM score. Conclusion: PRISM III and PIM scores are both adequate indicators of mortality probability for heterogeneous patient groups in pediatric intensive care. Possibly in larger studies (equivalence trial) a significant and relevant difference between these scores would be demonstrated.