Scoring systems for use in intensive care unit (ICU) patients have been introduced and developed over the last 30 years. They allow an assessment of the severity of disease and provide an estimate of in-hospital mortality. This estimate is achieved by collating routinely measured data specific to a patient . A weighting is applied to each variable, and the sum of the weighted individual scores produces the severity score. Various factors have been shown to increase the risk of in-hospital mortality after admission to ICU, including increasing age and severity of acute illness, certain pre-existing medical conditions (e.g. malignancy, immunosuppression, and requirement for renal replacement therapy), and emergency admission to ICU. Before the 1980s, there were no scoring systems applicable to critical care populations which would allow outcomes from different critical care units to be compared. Since then, many scoring systems have been developed, though only a small minority are used. Several of these systems are known simply by their acronym (e.g. APACHE and MODS).
