title: Performance of APACHE III over time in Australia and New Zealand: a retrospective cohort study.
abstract: The Acute Physiology and Chronic Health Evaluation (APACHE) III-j model has been used for benchmarking intensive care unit (ICU) outcomes in Australia and New Zealand for over a decade. This study assessed performance of the APACHE III-j model in adult patients admitted to Australasian ICUs during a ten-year period. Data were extracted from the Australian and New Zealand Intensive Care Society Adult Patient Database. Performance of APACHE III-j at different time points and within different age strata was evaluated by dividing the whole cohort into five 'two-year' groups. Calibration and discrimination were assessed by the Brier score, Hosmer-Lemeshow C and H statistics, Standardised Mortality Ratio (SMR), Cox calibration regression, calibration curves and area under the receiver operating characteristic curve (AUROC). Model performance within diagnostic categories was evaluated.   Between 1 January 2000 and 31 December 2009, 558,585 ICU admissions which met inclusion criteria were included in the analysis. The mean (standard deviation) age was 60.8 (18.4) years and 58.3% were male. Overall observed mortality was 12.6%. The mean (standard deviation) APACHE III-j predicted mortality was 14.5% (21.8). Although discrimination (as measured by AUROC) was preserved over time, all other markers of model performance showed deterioration. There was a significant decrease in SMR in eight of ten most common diagnoses examined.  This study demonstrates that performance of APACHE III-j model has deteriorated in Australasian hospitals and there is now a clear need for an updated modelling approach to improve mortality prediction, performance monitoring and quality of research undertaken in Australian and New Zealand ICUs.
authors.affiliation: Australian and New Zealand Intensive Care Research Centre, Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Victoria, Australia. eldho.paul@monash.edu
authors.forename: E
authors.initials: E
authors.lastname: Paul
authors.forename: M
authors.initials: M
authors.lastname: Bailey
authors.forename: A
authors.initials: A
authors.lastname: Van Lint
authors.forename: V
authors.initials: V
authors.lastname: Pilcher
mesh_terms: D018806:APACHE; D000328:Adult; D000368:Aged; D001315:Australia; D019985:Benchmarking / Q000379:methods*; D002138:Calibration; D015331:Cohort Studies; D016208:Databases, Factual; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D009520:New Zealand; D012372:ROC Curve; D012189:Retrospective Studies; D013997:Time Factors