SAPS II
Simplified Acute Physiology Score II — ICU mortality prediction.
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Why use it
No primary diagnosis required. Widely used in Europe and internationally as an ICU benchmarking and mortality prediction tool.
About
SAPS II (Simplified Acute Physiology Score II) is a severity-of-illness scoring system used in ICUs to predict hospital mortality. It is based on 17 variables collected within the first 24 hours of ICU admission.
When to use
- ICU patients within first 24 hours of admission
- Benchmarking ICU performance
- Research and quality improvement
- Complementary to APACHE II/SOFA
Formula
17 variables: age, HR, SBP, temp, PaO2/FiO2 (if ventilated), urine output, BUN, WBC, K+, Na+, HCO3-, bilirubin, GCS, chronic disease type, admission type
Predicted mortality: logit = -7.7631 + 0.0737×SAPS + 0.9971×ln(SAPS+1)
Probability = e^logit / (1+e^logit)
Pearls & pitfalls
- Use worst values in first 24 hours of ICU stay.
- Score alone predicts group mortality; individual predictions require caution.
- More granular than APACHE II for some physiologic derangements.
- Does not require primary diagnosis for calculation (unlike APACHE II).
Next steps
Calculate logit = -7.7631 + 0.0737×score + 0.9971×ln(score+1). Predicted mortality = e^logit / (1+e^logit). Use for benchmarking, not individual prognostication.
Evidence
Le Gall et al. JAMA 1993. Derived in 13,152 ICU patients across 137 units (Europe/North America). AUC 0.86 for hospital mortality.
References
- 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. — link