Saps Ii Score Calculator
Calculate ICU mortality probability using the Simplified Acute Physiology Score II. Enter values for instant results with step-by-step formulas.
Reviewed by Rahul Singh, Health & Wellness Specialist
Formula
logit = -7.7631 + 0.0737 * Score + 0.9971 * ln(Score + 1); Mortality = e^logit / (1 + e^logit)
The SAPS II score is the sum of points from 17 variables (age, heart rate, systolic BP, temperature, GCS, PaO2/FiO2, urine output, BUN, WBC, potassium, sodium, bicarbonate, bilirubin, chronic disease, admission type). The logistic regression equation converts the score to a predicted hospital mortality probability.
Worked Examples
Example 1: Moderate Severity Sepsis Patient
Problem:A 68-year-old medical admission with HR 110, SBP 85, Temp 39.2, GCS 13, BUN 45 mg/dL, WBC 18, K+ 4.2, Na+ 138, HCO3 19, Bili 1.5, urine output 800 mL/day, no chronic disease, not ventilated.
Solution:Age 68: 12 points\nHR 110: 0 points\nSBP 85: 5 points\nTemp 39.2: 3 points\nGCS 13: 5 points\nBUN 45: 6 points\nWBC 18: 0 points\nK+ 4.2: 0 points\nNa+ 138: 0 points\nHCO3 19: 3 points\nBili 1.5: 0 points\nUrine 800 mL: 4 points\nMedical admission: 6 points\nTotal = 44 points
Result:SAPS II Score: 44 | Predicted Mortality: ~35%
Example 2: High Severity Post-Cardiac Arrest
Problem:A 55-year-old unscheduled surgical admission with HR 130, SBP 65, Temp 35.5, GCS 4, BUN 60 mg/dL, WBC 22, K+ 5.8, Na+ 148, HCO3 14, Bili 2.0, urine output 300 mL/day, on mechanical ventilation with PaO2/FiO2 150.
Solution:Age 55: 7 points\nHR 130: 4 points\nSBP 65: 13 points\nTemp 35.5: 0 points\nGCS 4: 26 points\nPaO2/FiO2 150 (ventilated): 9 points\nBUN 60: 6 points\nWBC 22: 3 points\nK+ 5.8: 3 points\nNa+ 148: 1 point\nHCO3 14: 6 points\nBili 2.0: 0 points\nUrine 300 mL: 11 points\nUnscheduled surgery: 8 points\nTotal = 97 points
Result:SAPS II Score: 97 | Predicted Mortality: ~95%
Frequently Asked Questions
What is the SAPS II scoring system?
The Simplified Acute Physiology Score II (SAPS II) is an ICU severity-of-illness scoring system developed by Le Gall and colleagues in 1993 to predict hospital mortality for ICU patients. It uses 17 variables including 12 physiological measurements, age, type of admission, and three underlying disease variables collected within the first 24 hours of ICU admission. The score produces a predicted hospital mortality rate through a logistic regression equation. SAPS II has been validated across multiple international populations and remains one of the most widely used ICU prognostic tools. It was designed to be simpler than the original APACHE systems while maintaining strong predictive accuracy for population-level mortality estimation.
When should the SAPS II score be calculated?
The SAPS II score should be calculated using the worst values from the first 24 hours of ICU admission. This means clinicians should record the most abnormal value for each physiological variable during that initial 24-hour window. For heart rate and blood pressure, the worst value means the one that generates the highest point score, which could be either the highest or lowest recorded value depending on the variable. The score is typically calculated once at admission and is not meant to be recalculated daily, unlike some other scoring systems. If a patient is transferred from another ICU, the 24-hour window begins at the time of admission to the first ICU. The Glasgow Coma Scale should be assessed before sedation when possible.
How accurate is the SAPS II mortality prediction?
The SAPS II system demonstrates good discrimination with an area under the receiver operating characteristic curve (AUROC) typically between 0.80 and 0.87 in validation studies, meaning it correctly ranks patients by mortality risk approximately 80 to 87 percent of the time. However, calibration can vary significantly across different hospital populations, time periods, and geographic regions. The original model was developed using data from 1991-1992, and ICU care has improved substantially since then, meaning SAPS II may overestimate mortality in modern ICU settings. For individual patient prognostication, the score should never be used in isolation to make treatment decisions. It is most appropriately used for benchmarking ICU performance, comparing severity across populations, and risk-adjusting outcomes research.
What is the difference between SAPS II and APACHE scores?
SAPS II and APACHE are both ICU severity scoring systems but differ in complexity and design. SAPS II uses 17 variables and was specifically designed to be simpler and faster to calculate than APACHE, which uses up to 142 variables in the APACHE IV version. SAPS II does not require a specific primary diagnosis, while APACHE IV incorporates the primary ICU admission diagnosis into its prediction model, potentially improving accuracy for certain conditions. APACHE systems generally have slightly better discrimination in some studies but require more data collection effort. SAPS II is more commonly used in European ICUs, while APACHE is more prevalent in North American units. Both systems share the fundamental approach of using physiological derangement in the first 24 hours to predict outcomes.
References
Reviewed by Rahul Singh, Health & Wellness Specialist · Editorial policy