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PIM2: a revised version of the Paediatric Index of Mortality
Anthony Slater1, Frank Shann, Gale Pearson
1Women's and Children's Hospital, 72 King William Road, SA 5006, North Adelaide, Australia. slatera@wch.sa.gov.au
Insights
The Paediatric Index of Mortality 2 (PIM2) was revised to account for improved paediatric intensive care outcomes. This updated PIM2 model accurately estimates mortality risk for continuous quality monitoring.
Area of Science:
- Pediatric Intensive Care Medicine
- Health Services Research
- Clinical Epidemiology
Background:
- Paediatric intensive care has seen significant improvements in outcomes.
- Existing mortality prediction models may not accurately reflect these advancements.
- A revised index is needed for effective quality assessment.
Purpose of the Study:
- To revise the Paediatric Index of Mortality (PIM) to adjust for improved outcomes in paediatric intensive care.
- To develop an updated tool for assessing paediatric intensive care unit (PICU) performance.
Main Methods:
- International, multi-centre, prospective, observational study involving 12 specialist and 2 combined adult/paediatric ICUs.
- Logistic regression was used for variable selection to develop a revised model.
- Data from 20,787 patient admissions were analyzed, with a learning model tested against separate data.
Main Results:
- A revised model, PIM2, was developed incorporating three new variables related to ICU admission reason.
- The model demonstrated good fit (chi(2) 8.14, p=0.42) and discrimination (ROC 0.90) on test data.
- The final PIM2 model, using all data, also showed excellent fit and discrimination (chi(2) 11.56, p=0.17; ROC 0.90).
Conclusions:
- PIM2 is a re-calibrated tool reflecting improvements in paediatric intensive care.
- It accurately estimates mortality risk using data available at ICU admission.
- PIM2 is suitable for continuous monitoring of paediatric intensive care quality.
Objective:
To revise the Paediatric Index of Mortality (PIM) to adjust for improvement in the outcome of paediatric intensive care.
Design:
International, multi-centre, prospective, observational study.
Setting:
Twelve specialist paediatric intensive care units and two combined adult and paediatric units in Australia, New Zealand and the United Kingdom.
Patients:
All children admitted during the study period. In the analysis, 20787 patient admissions of children less than 16 years were included after 220 patients transferred to other ICUs and one patient still in ICU had been excluded.
Interventions:
None.
Measurements And Results:
A revised model was developed by forward and backward logistic regression. Variable selection was based on the effect of including or dropping variables on discrimination and fit. The addition of three variables, all derived from the main reason for ICU admission, improved the fit across diagnostic groups. Data from seven units were used to derive a learning model that was tested using data from seven other units. The model fitted the test data well (deciles of risk goodness-of-fit chi(2 )8.14, p=0.42) and discriminated between death and survival well [area under the receiver operating characteristic (ROC) plot 0.90 (0.89-0.92)]. The final PIM2 model, derived from the entire sample of 19638 survivors and 1104 children who died, also fitted and discriminated well [chi(2 )11.56, p=0.17; area 0.90 (0.89-0.91)].
Conclusions:
PIM2 has been re-calibrated to reflect the improvement that has occurred in intensive care outcome. PIM2 estimates mortality risk from data readily available at the time of ICU admission and is therefore suitable for continuous monitoring of the quality of paediatric intensive care.
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