• Vol. 44 No. 4
  • 15 April 2015

An External Independent Validation of APACHE IV in a Malaysian Intensive Care Unit



Introduction: Intensive care unit (ICU) prognostic models are predominantly used in more developed nations such as the United States, Europe and Australia. These are not that popular in Southeast Asian countries due to costs and technology considerations. The purpose of this study is to evaluate the suitability of the acute physiology and chronic health evaluation (APACHE) IV model in a single centre Malaysian ICU.

Materials and Methods: A prospective study was conducted at the single centre ICU in Hospital Sultanah Aminah (HSA) Malaysia. External validation of APACHE IV involved a cohort of 916 patients who were admitted in 2009. Model performance was assessed through its calibration and discrimination abilities. A first-level customisation using logistic regression approach was also applied to improve model calibration.

Results: : APACHE IV exhibited good discrimination, with an area under receiver operating characteristic (ROC) curve of 0.78. However, the model’s overall fi t was observed to be poor, as indicated by the Hosmer-Lemeshow goodness-of-fi t test (Ĉ = 113, P <0.001). Predicted in-ICU mortality rate (28.1%) was significantly higher than the actual in-ICU mortality rate (18.8%). Model calibration was improved after applying first-level customisation (Ĉ = 6.39, P = 0.78) although discrimination was not affected

Conclusion: APACHE IV is not suitable for application in HSA ICU, without further customisation. The model’s lack of fi t in the Malaysian study is attributed to differences in the baseline characteristics between HSA ICU and APACHE IV datasets. Other possible factors could be due to differences in clinical practice, quality and services of health care systems between Malaysia and the United States.

Over the past 30 years, different versions of severity of illness scoring systems and prognostic models have been developed for prediction of patient outcomes in critical care. These physiological-based systems and models allow patients to be stratified according to their severity of illness and provide prediction of in-hospital mortality. The concept of using intensive care unit (ICU) prognostic models is considered relatively new in Malaysia, despite these models being widely applied in most developed nations. At present, performance assessment of ICUs across the country is managed by the Malaysian Registry of Intensive Care (MRIC), through annual national audits. Assessment and rating of performance in ICUs is primarily based on computation of the simplified acute physiology score (SAPS) II severity of illness scores. A limitation of this assessment is that it considers only the severity of illness scoring component alone, without fully utilising the prediction component. In our opinion, the current assessment approach can be further improved through implementation of a suitable prognostic model that not only provides a severity of illness stratification system, but is also capable of predicting objective mortality risk estimates.

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