APACHE II Calculator
Estimate ICU mortality risk using the APACHE II scoring system.
Physiological Variables
Age & Chronic Health
APACHE II Score
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About
This APACHE II calculator estimates adult ICU severity and in-hospital mortality risk using the Acute Physiology and Chronic Health Evaluation II score. APACHE II is calculated from the worst values of 12 physiological variables in the first 24 hours of ICU admission plus age and chronic health points. It is one of the most extensively validated ICU severity scores and remains widely used for case-mix adjustment, severity stratification on admission, and research benchmarking despite the existence of APACHE III and IV. Use APACHE II as a one-time admission-day score; use the SOFA score instead when serial daily organ-dysfunction tracking is the goal (SOFA underlies the Sepsis-3 definition: a ≥2-point rise with suspected infection diagnoses sepsis), and consider SAPS II for mixed-population mortality prediction (more common in European cohorts). APACHE II is not validated outside the ICU, in dedicated coronary care unit cohorts, in burns patients (use Burns BSA / Parkland), or in paediatric populations.
Formula
Interpretation
| APACHE II Score | Approximate Mortality |
|---|---|
| 0 – 4 | ~4% |
| 5 – 9 | ~8% |
| 10 – 14 | ~15% |
| 15 – 19 | ~25% |
| 20 – 24 | ~40% |
| 25 – 29 | ~55% |
| 30 – 34 | ~73% |
| ≥ 35 | ~85% |
Mortality bands are from the Knaus 1985 derivation cohort (medical and surgical ICU patients, early 1980s). Discrimination remains good in contemporary populations (rank order is preserved), but absolute mortality is systematically over-predicted owing to advances in ICU care since publication; APACHE III/IV recalibrated coefficients address this.
References
- Knaus WA, et al. APACHE II: a severity of disease classification system. Crit Care Med. 1985;13(10):818-829.
- Capuzzo M, et al. Validation of severity scoring systems SAPS II and APACHE II in a single-center population. Intensive Care Med. 2000;26(12):1779-1785.
- Vincent JL, et al. The SOFA (Sepsis-related Organ Failure Assessment) score to describe organ dysfunction/failure. Intensive Care Med. 1996;22(7):707-710.
- Le Gall JR, et al. A new Simplified Acute Physiology Score (SAPS II) based on a European/North American multicenter study. JAMA. 1993;270(24):2957-2963.
FAQ
Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.