Table 4.

Comparison of risk prediction scoring systems

Risk prediction system	Description	Advantages	Disadvantages
American Society of Anesthetists	Numerical scale (1 to 5) based on severity of co-morbidities	Simple, easily applied, well known	Subjective, not individual or procedure specific, poor sensitivity and specificity
Charlson Comorbidity Score	Additive score based on weighting of preoperative diseases	Simple, better predictor than American Society of Anesthetists, good at estimating population risk	Subjective, does not look at procedure, mainly used as a research tool
Revised Cardiac Risk Index	Scoring system based on presence of one of six major co-morbidities and the severity of operation	Simple, well validated and good for predicting cardiac risk	Single-organ risk, broad categories, assessment of severity of operation is subjective
Acute Physiology and Chronic Health Evaluation	12 to 17 variables, measured over 24 hours	Individualised predictor of risk of mortality and morbidity, better predictor of outcome than American Society of Anesthetists, well known	Multiple variables over 24 hours of critical care, can be difficult to score before emergent surgery, not designed for use perioperatively
Simplified Acute Physiology Score	17 variables measured over 24 hours	Well validated for predictive mortality	Multiple variables over 24 hours of critical care, can be difficult to score before emergent surgery, not designed for use perioperatively
Physiological and Operative Severity Score for the Enumeration of Mortality and Morbidity	Scoring of 12 physiological and six operative variables, which are then entered into two mathematical equations to predict mortality and morbidity	Best validated and known/used scores for perioperative prediction various surgery-specific variations for specific areas	May overestimate or underestimate mortality and morbidity in specific populations due to use of logarithmic regression