Development of a Model for Comparing Risk-adjusted Mortality Rates of Acute Myocardial Infarction Patients

Park, Hyeung-Keun; Ahn, Hyeong-Sik

Journal of Korean Society Quality Assurance Health Care 2003;10(2): 216.
Published online December 30, 2003.

급성심근경색증 환자의 진료 질 평가를 위한 병원별 사망률 예측 모형 개발

박형근¹, 안형식²

¹한국보건산업진흥원
²고려대학교 의과대학 예방의학교실

Development of a Model for Comparing Risk-adjusted Mortality Rates of Acute Myocardial Infarction Patients

Hyeung-Keun Park¹, Hyeong-Sik Ahn²

¹Korea Health Industry Development Institute
²Department of Preventive Medicine, College of Medicine, Korea University

Abstract

Objectives
To develop a model that predicts a death probability of acute myocardial infarction(AMI) patient, and to evaluate a performance of hospital services using the developed model.
Methods
Medical records of 861 AMI patients in 7 general hospitals during 1996 and 1997 were reviewed by two trained nurses. Variables studied were risk factors which were measured in terms of severity measures. A risk model was developed by using the logistic regression, and its performance was evaluated using cross-validation and bootstrap techniques. The statistical prediction capability of the model was assessed by using c-statistic, $R^2$ as well as Hosmer-Lemeshow statistic. The model performance was also evaluated using severity-adjusted mortalities of hospitals.
Results
Variables included in the model building are age, sex, ejection fraction, systolic BP, congestive heart failure at admission, cardiac arrest, EKG ischemia, arrhythmia, left anterior descending artery occlusion, verbal response within 48 hours after admission, acute neurological change within 48 hours after admission, and 3 interaction terms. The c statistics and $R^2$ were 0.887 and 0.2676. The Hosmer-Lemeshow statistic was 6.3355 (p-value=0.6067). Among 7 hospitals evaluated by the model, two hospitals showed significantly higher mortality rates, while other two hospitals had significantly lower mortality rates, than the average mortality rate of all hospitals. The remaining hospitals did not show any significant difference.
Conclusion
The comparison of the qualities of hospital service using risk-adjusted mortality rates indicated significant difference among them. We therefore conclude that risk-adjusted mortality rate of AMI patients can be used as an indicator for evaluating hospital performance in Korea.

Key words Acute myocardial infarction;Risk adjustment;Hospital Mortality;