Risk prediction of hospital mortality for adult patients admitted to Australian and New Zealand intensive care units: development and validation of the Australian and New Zealand Risk of Death model.
OBJECTIVE
The purpose of this study is to develop and validate a new mortality prediction model (Australian and New Zealand Risk of Death [ANZROD]) for Australian and New Zealand intensive care units (ICUs) and compare its performance with the existing Acute Physiology and Chronic Health Evaluation (APACHE) III-j.


METHODS
All ICU admissions from 2004 to 2009 were extracted from the Australian and New Zealand Intensive Care Society Adult Patient Database. Hospital mortality was modeled using logistic regression with training (two third) and validation (one third) data sets. Predictor variables included APACHE III score components, source of admission to ICU and hospital, lead time, elective surgery, treatment limitation, ventilation status, and APACHE III diagnoses. Model performance was assessed by standardized mortality ratio, Hosmer-Lemeshow C and H statistics, Brier score, Cox calibration regression, area under the receiver operating characteristic curve, and calibration curves.


RESULTS
There were 456605 patients available for model development and validation. Observed mortality was 11.3%. Performance measures (standardized mortality ratio, Hosmer-Lemeshow C and H statistics, and receiver operating characteristic curve) for the ANZROD and APACHE III-j model in the validation data set were 1.01, 104.9 and 111.4, and 0.902; 0.84, 1596.6 and 2087.3, and 0.885, respectively.


CONCLUSIONS
The ANZROD has better calibration; discrimination compared with the APACHE III-j. Further research is required to validate performance over time and in specific subgroups of ICU population.
Australian and New Zealand Intensive Care Research Centre, Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia. Electronic address: eldho.paul@monash.edu.
Eldho
E
Paul
Michael
M
Bailey
David
D
Pilcher
D018806:APACHE; D000328:Adult; D001315:Australia / Q000453:epidemiology; D016638:Critical Illness / Q000401:mortality*; D016208:Databases, Factual; D005260:Female; D006305:Health Status Indicators; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D011237:Predictive Value of Tests; D018570:Risk Assessment / Q000379:methods*
ANZROD; Intensive care; Mortality prediction; SMR