Modification of Acute Physiology and Chronic Health Evaluation II score through recalibration of risk prediction model in critical care patients of a respiratory disease referral center

BACKGROUND: Several models have been developed to measure the severity of illness in intensive care unit (ICU) patients, It is suggested that the models should be customized depending on the characteristics of different population of patients. This study is aimed to assess and modify the performance of Acute Physiology and Chronic Health Evaluation II (APACHE-II) model in a respiratory diseases referral center. MATERIALS AND METHODS: A total of 730 patients, admitted to an intensive care unit during one year, were divided into two sets (71% training and 29% test). Our modified APACHE-II model was developed and calibrated on training set. Then, the integrity of the customized model was checked and compared to the original APACHE-II, on the test set. Logistic regression was used to develop ROC analysis, F-measure and kappa coefficient and were employed to calibrate the model. RESULTS: Both Original and Our modified APACHE-II scores performed acceptable discriminative power (AUC = 0.908: 95%CI 0.861-0.854; and AUC = 0.856: 95%CI 0.789-0.923, respectively); the difference was not significant (P = 0.132). Our modified APACHE-II showed improved accuracy (87.9% vs. 84.1%) and sensitivity (56.4% vs. 16.3%) compared to the original model. F-measure and Kappa also gave the impression of improvement for our modified APACHE-II system. CONCLUSION: The results demonstrated that a modified APACHE-II system in a local ICU of respiratory disease could have similar discrimination and comparable calibration to the original model.