Performance of the pediatric index of mortality 2 (PIM-2) in cardiac and mixed intensive care units in a tertiary children’s referral hospital in Italy

Abstract

BackgroundMortality rate of patients admitted to Intensive Care Units is a widely adopted outcome indicator. Because of large case-mix variability, comparisons of mortality rates must be adjusted for the severity of patient illness at admission. The Pediatric Index of Mortality 2 (PIM-2) has been widely adopted as a tool for adjusting mortality rate by patients’ case mix. The objective of this study was to assess the performance of PIM-2 in children admitted to intensive care units after cardiac surgery, other surgery, or for other reasons.MethodsThis was a prospective cohort study, conducted in a 607 inpatient-bed tertiary-care pediatric hospital in Italy, with three pediatric intensive care Units (PICUs) and one cardiac Unit (CICU). In 2009–11, all consecutive admissions to PICUs/CICU of children aged 0–16 years were included in the study. Discrimination and calibration measures were computed to assess PIM-2 performance. Multivariable logistic regression analysis was used to assess the association of patients’ main reason for intensive care admission (cardiac-surgical, other-surgical, medical), age, Unit and year with observed mortality, adjusting for PIM-2 score.ResultsPIM-2 data collection was completed for 91.2% of total PICUs/CICU patient admissions (2912), and for 94.8% of patients who died in PICUs/CICU (129). Overall observed mortality was 4.4% (95% CI, 3.7-5.2), compared to 6.4% (95% CI, 5.5-7.3) expected mortality. Standardised mortality ratio was 0.7 (95% CI: 0.6-0.8). PIM-2 discrimination was fair (area under the curve, 0.79; 95% CI: 0.75-0.83). Calibration was less satisfactory, mainly because of the over two-fold overprediction of deaths in the highest risk group (114.7 vs 53; p < 0.001), and particularly in cardiac-surgical patients. Multivariable logistic analysis showed that risk of death was significantly reduced in cardiac-surgical patients and in those aged 1 month to 12 years, independently from PIM-2.ConclusionsThe children age distribution and the proportion of cardiac-surgical patients should be taken into account when interpreting SMRs estimated using the PIM-2 prediction model in different Units. A new calibration study of PIM-2 score might be needed, and more appropriate cardiac-focused risk-adjustment models should be developed. The role of age on risk of death needs to be further explored.

Pediatric Index of Mortality 2 as a predictor of death risk in children admitted to pediatric intensive care units in Latin America: A prospective, multicenter study

“…It is likely that in this group of patients, given the low prevalence of CCC (1.2%), the advances in the treatment of critically ill patients have become evident; having improved the prognosis from the time PIM2 was developed. In some populations, these changes have resulted in an observed mortality lower than predicted by PIM2 [31]. This finding has not been evidenced in our sample in the postsurgical patients nor in the miscellaneous diagnoses group, in which the number of observed deaths was higher than the number of deaths predicted by the score, coinciding with what is observed in the general population.…”

“…Ciofi degli Atti also reported an inadequate calibration of the score in adolescents. These differences could be explained considering that age is not a variable included in the calculation of the score, despite the fact that adolescents are different in many aspects from adults or preadolescents [31,32].…”

Assessment of the performance of the Pediatric Index of Mortality 2 (PIM2) among Egyptian pediatric patients admitted to the intensive care

“…15 A prospective study of PIM2 performance in 3 Italian PICUs and one cardiac intensive care unit reported an observed mortality of 4.4% and a predicted mortality of 6.4%, SMR is 0.7 (95% CI 0.6-0.8). 1 In Argentina, a prospective cohort study documented an observed mortality of 2.6% in PICU compared to a PIM2 predicted mortality of 3.06%. 19 A cohort study among children admitted to three PICU settings in Hong Kong revealed a PIM2 predicted mortality (14.2 deaths) compared to 7 observed deaths, SMR is 0.49 (95% CI 0.13 to 0.86).…”

“…1 Several scoring models that predict the risk of mortality of pediatric patients admitted to the intensive care are available. 2,3 Mortality prediction models are useful in PICU settings as risk assessment tools and as a benchmark for the quality of care between facilities.…”

Validation of the Pediatric Index of Mortality 2 (PIM2) in Argentina: a prospective, multicenter, observational study

“…There might be an explanation for such difference because age is not a variable included in the score estimation even though adolescents are different in many aspects compared to adults or pre-adolescents. 21,22 In the analysis of the performance of the PIM2 score stratified by diagnosis group on admission, an adequate discrimination for all categories was observed, except for patients with a diagnosis of a respiratory disease on admission. The calibration also evidenced significant differences between observed and predicted deaths in this group (105 versus 81, p = 0.03).…”