APACHE II Score in ICU: Purpose and Clinical Application
The APACHE II (Acute Physiology and Chronic Health Evaluation II) score is the most effective tool for predicting mortality in ICU patients, with superior discriminative power (pooled AUC of 0.81) compared to other scoring systems, and is used primarily to assess disease severity and predict mortality risk in critically ill patients. 1
Overview of APACHE II Score
- APACHE II was introduced in 1985 to reflect both premorbid factors (patient age and chronic medical conditions) and acute changes in 12 physiologic parameters 1
- The score provides a comprehensive assessment of patient severity by evaluating chronic health status and physiological measurements 2
- APACHE II has demonstrated the highest accuracy for predicting severe acute conditions compared to other scoring systems 1
Components and Calculation
- APACHE II incorporates 12 physiologic variables, age, type of hospital admission, and chronic health evaluation 2, 3
- The score is calculated within the first 24 hours of ICU admission, providing an early assessment of patient severity 4
- Unlike other scoring systems such as SOFA, APACHE II includes age and comorbidities, which are important factors in predicting outcomes 1, 5
Clinical Applications
- APACHE II serves as a valuable prognostic tool for research, particularly when evaluating mortality, morbidity, and quality of life outcomes in critically ill patients 2
- The score helps in risk stratification to account for case mix in clinical studies and comparison of quality of care among ICUs 6
- An APACHE II score of 15 provides the best diagnostic accuracy to predict mortality of critically ill patients with a sensitivity of 85.3% and specificity of 77.4% 4
- The score has demonstrated very good discriminatory performance with an accuracy rate of 75% and an AUC-ROC of 0.80 in predicting ICU mortality in patients with sepsis 7
Advantages Over Other Scoring Systems
- APACHE II outperforms SOFA in discriminative power for mortality prediction (AUC 0.81 vs. 0.75) 1
- Unlike SOFA, APACHE II is suitable for categorizing patients with varying severity levels, including those without sepsis or organ failure within 24 hours of hospital admission 1, 5
- APACHE II considers age and chronic health conditions, which SOFA does not include in its assessment 1, 3
Timing of Assessment
- While traditionally calculated within the first 24 hours of ICU admission, research suggests that Day 3 APACHE II score may be the optimal time point for predicting hospital mortality 8
- Day 3 APACHE II score with a cutoff of 17 has shown excellent sensitivity (92.8%) for identifying non-survivors 8
Common Pitfalls and Considerations
- The score may overpredict mortality in some settings, as observed mortality rates can differ from predicted rates after effective treatment 9
- APACHE II should be interpreted in the context of the specific patient population, as its predictive value may vary across different critical conditions 9
- Regular recalculation of the score can provide valuable information about patient progress and response to treatment 3