Abstract
Severity scales are important adjuncts of treatment in the intensive care unit (ICU) in order to predict patient outcome, comparing quality-of-care and stratification for clinical trials. Even though disease severity scores are not the key elements of treatment, they are however, an essential part of improvement in clinical decisions and in identifying patients with unexpected outcomes. Prediction models do face many challenges, but, proper application of these models helps in decision making at the right time and in decreasing hospital cost. In fact, they have become a necessary tool to describe ICU populations and to explain differences in mortality. However, it is also important to note that the choice of the severity score scale, index, or model should accurately match the event, setting or application; as mis-application, of such systems can lead to wastage of time, increased cost, unwarranted extrapolations and poor science. This article provides a brief overview of ICU severity scales (along with their predicted death/survival rate calculations) developed over the last 3 decades including several of them which has been revised accordingly.