A critical appraisal and systematic review of illness severity scoring systems in the intensive care unit

In this document we critically review the development and use of general intensive care unit admission severity of illness scoring systems. Data sources for this review included a computerized bibliographic search and published proceedings from relevant conferences in critical care medicine. Current severity of illness scoring systems have been developed through rigorous, iterative research evaluating their accuracy, content validity, and applicability. The relative value of Acute Physiology and Chronic Health Evaluation II and III, Mortality Probability Model II, and Simplified Acute Physiology Score II models depends on the intended purposes and settings. These severity scoring systems are better suited to estimate the probability of hospital mortality for intensive care unit populations than to predict death and determine care for individuals. In the former role, severity scoring systems have revolutionized critical care. However, limitations include the omission of long-term functional status and quality-of-life measures, as well as comparisons of current models. These are ideal areas for future research.