Several scoring systems have been developed to grade the severity of illness in critically ill patients. These systems are moderately accurate in predicting individual survival. However, these systems are more valuable for monitoring quality of care and for conducting research studies because they allow comparison of outcomes among groups of critically ill patients with similar illness severity.
One of the most common systems is the 2nd version of the Acute Physiologic Assessment and Chronic Health Evaluation II (APACHE II) score introduced in 1985. It generates a point score ranging from 0 to 71 based on 12 physiologic variables, age, and underlying health (see table APACHE II Scoring System Acute Physiologic Assessment and Chronic Health Evaluation (APACHE) II Scoring System* 
). The APACHE III system was developed in 1991, and the APACHE IV system was developed in 2006. These systems are more complex with a greater number of physiologic variables but are more cumbersome and are somewhat less used. There are many other systems, including the 2nd Simplified Acute Physiology Score (SAPS II), the Mortality Prediction Model (MPM), and the Sequential Organ Failure Assessment (SOFA) score Sequential Organ Failure Assessment (SOFA) Score .
