Discussion

    Modern paediatric intensive care is characterized by increased sophistication, resulting in spiralling costs. Auditing the PICU is thus an integral component in health care planning and management. There is a need to accurately define prognosis, so that the physician can be guided in clinical decision-making, including the appropriateness of therapy. Moreover, the impact of new technologies and medical intervention can be assessed in a more objective fashion.

Wells et al., attributes the difficulties in achieving exactly the same progress for two patients with the same level of clinical instability, i.e. the same prognostic score results, to two basic causes. The first cause is the differences in individual clinical conditions that are not evaluated by the score, such as, for example, the nutritional status or physical reserves of each individual.     The second cause is the differences in working conditions and infrastructure at each PICU. Units with greater availability of machines and medication can offer their patients treatment more quickly and thus impact on their progress. mortality. All of them offer a good capacity of discrimination between survivors and non-survivors patients. With the exception of PIM2, all scores are tools with comparable performance at the prognostic evaluation of the pediatric patients admitted at a general Portuguese PICU.

    There is no consensus on which function is more important for a prognostic score: calibration or discrimination. Both are important for determining the adjustment capacity of a model. Which function is most important will depend on the objective for which the prognostic score is being used. If, for example to distinguish between those who are more likely to die from those who are more likely to survive, then the capacity to discriminate is most important, but, if, however, the reason for using a score is to compare observed and expected mortality at different intervals of severity, then calibration capacity is more important. However, in order to achieve a global evaluation of the score, both discrimination and calibration should be considered.

    It is clear that there are many variables unmeasured by the prognostic scores studied, which make it difficult to classify severity levels of different patients in different intensive care units and, therefore, to find a prognostic index model with an extraordinary calibration capacity. The great challenge is to identify which variables do not have a similar predictive power for the population being studied. The interpretation of the mortality index of a PICU is dependent of statistical factors such as sample size, mortality rate at each severity level and random variations in the study population. The most powerful variable will be that which, in addition to changing the score, is observed often, i.e. is to be found in many patients in the population. We should, therefore, seek the power of the variables that a most similar to the reality of our population.

    This study reinforces the need to use a representative and large number of units when assessing such risk adjustment methods in another country or health care system. A small or unrepresentative selection of units could lead to confusion between unit or overall system performance and the need to recalibrate the score. Even including all units may result in poor calibration, but this does not necessarily invalidate the scores as a simple recalibration of these scores can lead to their being useful and valid tools for that country or health care system.

    Any variation in risk-adjusted PICU mortality needs to be tempered by an assessment of variation in longer term outcome. A reduction in mortality is of dubious benefit if it is at the expense of increased severe morbidity. Standardized and reliable methods of measuring health status (or at least clinical status) are required for use in Portugal.