Comparison of outcome from intensive care admission after adjustment for case mix by the APACHE III prognostic system.

STUDY OBJECTIVES

To evaluate the acute physiology, age, chronic health evaluation III (APACHE III) scoring system in the context of general adult ICUs in the United Kingdom.

DESIGN

Prospective, noninterventional, cohort study.

SETTING

Seventeen general adult ICUs in a discrete area of southwest England.

PATIENTS

12,793 patients admitted between April 1, 1993 and December 31, 1995.

MEASUREMENTS

Sociodemographic and severity-of-illness data were collected for all patients admitted to the study units. Formal goodness-of-fit tests were applied and observed mortality was compared with that predicted by using the APACHE III system.

RESULTS

For the group of ICUs as a whole, the risk-adjusted standardized mortality ratio (SMR) was 1.23 (95% confidence intervals, 1.12-1.25). For 11 out of 17 ICUs, the SMR was significantly greater than unity (p < 0.05). Calibration, as tested by Hosmer-Lemeshow statistics, was poor (H2 = 312.54; C2 = 332.85; df = 8; p < 0.01); however, model discrimination was good with a total correct classification rate of 82.9% and an area under the receiver operating characteristic curve of 0.89.

CONCLUSIONS

The excess mortality observed after case-mix adjustment using the APACHE III system in this study may be the result of either poor intensive care performance as compared with the United States or a failure of the APACHE III equation to fit the UK data.