Chest
Volume 100, Issue 6, December 1991, Pages 1619-1636
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Clinical Investigations in Critical Care
The APACHE III Prognostic System: Risk Prediction of Hospital Mortality for Critically III Hospitalized Adults

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The objective of this study was to refine the APACHE (Acute Physiology, Age, Chronic Health Evaluation) methodology in order to more accurately predict hospital mortality risk for critically ill hospitalized adults. We prospectively collected data on 17,440 unselected adult medical/surgical intensive care unit (ICU) admissions at 40 US hospitals (14 volunteer tertiary-care institutions and 26 hospitals randomly chosen to represent intensive care services nationwide). We analyzed the relationship between the patient's likelihood of surviving to hospital discharge and the following predictive variables: major medical and surgical disease categories, acute physiologic abnormalities, age, preexisting functional limitations, major comorbidities, and treatment location immediately prior to ICU admission. The APACHE III prognostic system consists of two options: (1) an APACHE III score, which can provide initial risk stratification for severely ill hospitalized patients within independently defined patient groups; and (2) an APACHE III predictive equation, which uses APACHE III score and reference data on major disease categories and treatment location immediately prior to ICU admission to provide risk estimates for hospital mortality for individual ICU patients. A five-point increase in APACHE III score (range, 0 to 299) is independently associated with a statistically significant increase in the relative risk of hospital death (odds ratio, 1.10 to 1.78) within each of 78 major medical and surgical disease categories. The overall predictive accuracy of the first-day APACHE III equation was such that, within 24 h of ICU admission, 95 percent of ICU admissions could be given a risk estimate for hospital death that was within 3 percent of that actually observed (r2 = 0.41; receiver operating characteristic = 0.90). Recording changes in the APACHE III score on each subsequent day of ICU therapy provided daily updates in these risk estimates. When applied across the individual ICUs, the first-day APACHE III equation accounted for the majority of variation in observed death rates (r2 = 0.90, p<0.0001).

Section snippets

PATIENTS AND METHODS

The two major analytic steps in developing APACHE III were (1) the collection of an appropriate data base and (2) analysis to establish a final system design. First, we assembled a list of candidate variables and questions for each of the five major predictive constructs (major disease categories, acute physiology, age, comorbidities, and origin and timing of patient selection).

RESULTS

The majority (89 percent) of the 40 hospitals were nonprofit, and 54 percent were affiliated with a medical school. The average number of hospital beds was 359, the average number of ICU beds was 21, and the average number of ICU beds was 13. These characteristics reflect national statistics on the 1,691 US hospitals with 200 or more beds. Of the 42 ICUs studied, 71 percent were mixed medical-surgical, 16 percent were surgical, 10 percent were medical, and 3 percent represented other

CONCLUSION

Every day, clinicians and physicians engaged in clinical research make complex decisions regarding the scope and intensity of treatment or the potential value of new therapies that might be supported or enhanced by an accurate and objective measurement of patient risk. Indeed, many of the most important questions concerning the quality and appropriateness of advanced medical care cannot be fully addressed until patient risk is accurately assessed and reliably recorded. The completion of the

FINANCIAL DISCLOSURE

All the authors certify that affiliations with or involvement in any organization or entity with a direct financial interest in the subject matter or materials discussed in this article are disclosed as follows: Drs Knaus, Wagner, and Zimmerman and Ms Draper are each founders and minority equity shareholders of APACHE Medical Systems, Inc (AMS), a for-profit Delaware-based corporation that funded, in part, the research for the APACHE III study. AMS markets a software-based clinical information

ACKNOWLEDGMENTS

We would like to acknowledge the institutions that participated in the APACHE III data collection: St Mary's Hospital, East St Louis; White Memorial Hospital, Los Angeles; United Hospital, Clarkcsboro, WV; St Lukes-Roosevelt, New York; Cooper Medical Center, Camden, NJ; Monongahela Valley Hospital, Monongahela, Pa; Easton Hospital, Easton, Md; Burlington Medical Center, Burlington, Ia; Union Hospital, Union, NJ; St Lukes Hospital, Newburgh, NY; Wyandotte Hospital/Medical Center, Wyandotte,

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    Supported by the Agency for Health Care Policy and Research (grant No. HS05787); The John A. Hartford Foundation (grant No. 87267); the Department of Anesthesiology, George Washington University Medical Center; and APACHE Medical Systems, Inc. Dr Bastos was supported by a grant from the National Council of Scientific and Technology Development (CNPq), Brazil.

    Manuscript received May 15; revision accepted August 13.

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