SAPS II (Simplified Acute Physiology Score II)

Overview

SAPS II (Simplified Acute Physiology Score II) was published by Le Gall et al. in 1993 following a European/North American multicenter study of 13,152 ICU patients across 137 units. It succeeded the original SAPS (1984) with improved discriminatory power and broader validation. The score uses 17 variables — 12 physiology items, age, admission type, and one chronic disease category — all taken from the worst values in the first 24 hours of ICU admission.

Unlike organ-dysfunction-centric scores such as SOFA, SAPS II provides a direct estimate of in-hospital mortality probability via a logistic regression formula. Its range is 0–163 points, and the probability of death is calculated as: logit(p) = −7.7631 + 0.0737 × SAPS II + 0.9971 × ln(SAPS II + 1).

SAPS II remains in common use as a benchmark tool for ICU quality assessment and comparison across centres, though its age means calibration may vary in modern patient populations.

Variables & Points

Variable	Range / Category	Points
Age	< 40 years	0
	40 – 59 years	7
	60 – 69 years	12
	70 – 74 years	15
	75 – 79 years	16
	≥ 80 years	18
Type of Admission	Elective surgical	0
	Medical	6
	Emergency surgical	8
Chronic Disease	None	0
	Metastatic carcinoma	9
	Hematologic malignancy	10
	AIDS	17
Heart Rate (/min)	< 40	11
	40 – 69	2
	70 – 119	0
	120 – 159	4
	≥ 160	7
Systolic BP (mmHg)	< 70	13
	70 – 99	5
	100 – 199	0
	≥ 200	2
Temperature	< 39 °C	0
Temperature	≥ 39 °C	3
Glasgow Coma Scale	14 – 15	0
	11 – 13	5
	9 – 10	7
	6 – 8	13
	< 6	26
PaO₂/FiO₂ (mmHg) if ventilated	≥ 200	6
	100 – 199	9
	< 100	11
Urine Output (mL/24 h)	≥ 1000	0
	500 – 999	4
	< 500	11
BUN (mg/dL)	< 28	0
	28 – 83	6
	≥ 84	10
WBC (×10³/µL)	1 – 19.9	0
	≥ 20	3
	< 1	12
Potassium (mmol/L)	3.0 – 4.9	0
	< 3.0 or ≥ 5.0	3

Sodium (mmol/L)	125 – 144	0
	≥ 145	1
	< 125	5
Bicarbonate (mmol/L)	≥ 20	0
	15 – 19	3
	< 15	6
Bilirubin (mg/dL)	< 4.0	0
	4.0 – 5.9	4
	≥ 6.0	9

Use the worst (most abnormal) value recorded in the first 24 hours. PaO₂/FiO₂ is only scored if the patient was on mechanical ventilation or CPAP. If sedated, use the estimated pre-sedation GCS.

Interpretation

SAPS II Score	Estimated Hospital Mortality
< 29	~10 %
29 – 40	~25 %
41 – 52	~40 – 50 %
53 – 64	~60 – 75 %
≥ 65	> 80 %

Probability of hospital death: logit(p) = −7.7631 + 0.0737 × SAPS II + 0.9971 × ln(SAPS II + 1), then p = e^logit / (1 + e^logit). The Scores2Go app displays the calculated probability directly.

Literature

Le Gall JR, Lemeshow S, Saulnier F. A new simplified acute physiology score (SAPS II) based on a European/North American multicenter study. JAMA. 1993;270(24):2957–2963.

Zimmerman JE, Kramer AA, McNair DS, Malila FM. Acute Physiology and Chronic Health Evaluation (APACHE) IV: hospital mortality assessment for today's critically ill patients. Crit Care Med. 2006;34(5):1297–1310.

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