UK PICOS: Risk adjustment for paediatric intensive care


Using statistical techniques, it is possible to build models that predict how likely a patient is to experience a particular outcome or condition. These risk models (or prognostic models) can be used to ‘risk adjust’ outcomes by taking into account severity of illness in order to make fairer comparisons between health care providers.

At the time of this study, a number of risk adjustment methods for paediatric intensive care had been developed, but none had been validated for general use in the UK. The aim of this study was to identify the best risk adjustment method for outcomes in paediatric intensive care in the UK by:

  • assessing and comparing the current methods (PIM, PIM2, PRISM, PRISM III – 12 hours and PRISM III – 24 hours)
  • optimising the performance of the current methods (‘recalibrating’ the models) and comparing the methods following recalibration
  • comparing alternative health state valuation models for the HUI2 health related quality of life instrument
  • developing and assessing a model for risk adjustment of health status, as measured by HUI2, at six months following admission to a paediatric intensive care unit


All PICUs in the United Kingdom were invited to participate. Predicted probability of PICU mortality was calculated using the published algorithms for PIM, PIM2, and PRISM and compared with observed mortality. These scores, along with PRISM III-12 and PRISM III-24, whose algorithms are not published, were optimized for the United Kingdom.


22 UK paediatric intensive care units took part in the study and collected data on 10,197 children admitted to the unit between March 2001 and March 2002. 450 members of the general public took part in surveys to estimate health state valuation models for the HUI2. All published tools were found to have poor calibration but provided good discriminatory power. After estimation of UK-specific coefficients, only PIM2, PRISM III-12, and PRISM III-24 had satisfactory calibration. All models provided good discriminatory power. Funnel plots for all of the recalibrated models indicated that the risk-adjusted mortality for all units was consistent with random variation.


PIM2, PRISM III-12, and PRISM III-24 all were found to be suitable for use in a UK PICU setting. All tools provided similar conclusions in assessing the distribution of risk-adjusted mortality in UK PICUs. It now is important that these tools be used to monitor outcome and improve the quality of paediatric intensive care within the United Kingdom.

Who led the study? 

  • Dr Gareth Parry, Medical Care Research Unit, University of Sheffield 
  • Dr Christopher McCabe, Medical Care Research Unit, University of Sheffield 
  • Professor Kathy Rowan, ICNARC 

The study was funded by the Medical Research Council (Project: G9900013)


Jones S, Rantell K, Stevens K, Colwell B, Ratcliffe JR, Holland P, Rowan K, Parry GJ. Outcome at 6 months after admission for pediatric intensive care: a report of a national study of pediatric intensive care units in the United kingdom. Pediatrics 2006; 118(5):2101-8.

Brady AR, Harrison D, Black S, Jones S, Rowan K, Pearson G, Ratcliffe J, Parry GJ. Assessment and optimization of mortality prediction tools for admissions to pediatric intensive care in the United kingdom. Pediatrics 2006; 117(4):e733-42.