SAPS II score = sum of 17 weighted variables. For physiology variables, use the most abnormal value during the first 24 hours in ICU.

Variable	Categories and points
Age, years	<40: 0 40–59: 7 60–69: 12 70–74: 15 75–79: 16 ≥80: 18
Heart rate, /min	<40: 11 40–69: 2 70–119: 0 120–159: 4 ≥160: 7
Systolic blood pressure, mm Hg	<70: 13 70–99: 5 100–199: 0 ≥200: 2
Temperature, °C	<39: 0 ≥39: 3
Glasgow Coma Scale	14–15: 0 11–13: 5 9–10: 7 6–8: 13 <6: 26
PaO₂/FiO₂, mm Hg	Not receiving mechanical ventilation or CPAP: 0 ≥200 while receiving mechanical ventilation or CPAP: 6 100–199 while receiving mechanical ventilation or CPAP: 9 <100 while receiving mechanical ventilation or CPAP: 11
Urine output, L/24 h	≥1.0: 0 0.5–0.99: 4 <0.5: 11
Serum urea or BUN	Urea <10 mmol/L or BUN <28 mg/dL: 0 Urea 10–29.9 mmol/L or BUN 28–83 mg/dL: 6 Urea ≥30 mmol/L or BUN ≥84 mg/dL: 10
Serum sodium, mmol/L	<125: 5 125–144: 0 ≥145: 1
Serum potassium, mmol/L	<3.0: 3 3.0–4.9: 0 ≥5.0: 3
Serum bicarbonate, mmol/L	<15: 6 15–19: 3 ≥20: 0
Serum bilirubin	<68.4 µmol/L or <4.0 mg/dL: 0 68.4–102.5 µmol/L or 4.0–5.9 mg/dL: 4 ≥102.6 µmol/L or ≥6.0 mg/dL: 9
White cell count, ×10⁹/L	<1.0: 12 1.0–19.9: 0 ≥20: 3
Admission type	Scheduled surgical: 0 Medical: 6 Unscheduled surgical: 8
Metastatic cancer	No: 0 Yes: 9
Haematological malignancy	No: 0 Yes: 10
AIDS	No: 0 Yes: 17

Logit = −7.7631 + (0.0737 × SAPS II score) + [0.9971 × ln(SAPS II score + 1)].

Predicted hospital mortality (%) = 100 × e^logit ÷ (1 + e^logit).

This implementation requires every input before displaying a result rather than assigning reference categories to missing data.

Simplified Acute Physiology Score (SAPS II)