Critical care outcome prediction equation model, version 7

Mortality prediction models are used for benchmarking, audit, research, and epidemiology. This report describes the development and validation methodology, for version 7 of the critical care outcome prediction equation for monitoring adult intensive care unit (ICU) mortality risk.

This was a multiphase study incorporating data extraction, curation, aggregation, modelling, and validation applied to jurisdictional administrative datasets to model 90-day survival.

The study was conducted across 28 public and 19 private hospitals in state of Victoria, Australia, with an adult population of 5.28 million.

A total of 215,148 consecutive adult hospital separations receiving intensive care over 5 years, July 2019-June 2024, were included in the study.

The main outcome measures included the case fatality rate (CFR) and standardised 90-day mortality ratio (SMR) at the provider level with model fit assessed for calibration (Brier score; Hosmer-Lemeshow statistic [H₁₀]), discrimination (area under the receiver-operator characteristic and precision-recall curves), classification (CFR and SMR results for ICU-years classified within ±3 standard deviation [SD]), and dispersion (dispersion value [ϕ]; SD random effect [τ]) characteristics.

The CFR was found to be 12.0 (95% confidence interval: 11.8-12.1) per 100 separations and 16.1 (95% confidence interval: 15.7-16.4) per 100 persons. A total of 7771 (53.7%) admission diagnoses were aggregated into 24 clinical diagnosis groups and eight demographic (final) model variables. The following results were obtained: mean Brier score = 0.08; H₁₀ = 15.95; area under the receiver-operator characteristic curve = 0.85; area under the precision-recall curve = 0.43. A total of 126 (54.1%) CFR results and 220 (94.4%) SMR values were within ±3 SD. A total of 105 (45.3%) CFR-outlier ICU-years were reclassified as SMR inliers, with no CFR inlier reclassified as an SMR outlier. Overdispersion metrics: ϕ = 2.80; τ = 0.15.

Critical care outcome prediction equation, version 7 is a parsimonious hospital mortality prediction model for adult intensive care admissions, derived from administrative data common to all jurisdictions.