title: ICU severity of illness scores: APACHE, SAPS and MPM.
abstract: OBJECTIVE
  This review aims to evaluate the latest versions of the Acute Physiology and Chronic Health Evaluation, Simplified Acute Physiology Score and Mortality Probability Model scores, make comparisons and describe their strengths and limitations. Additionally, we provide critical analysis and recommendations for the use of these scoring systems in different scenarios.
  
  
  RESULTS
  The last generation of ICU scoring systems (Acute Physiology and Chronic Health Evaluation IV, Mortality Probability Model 0-III (MPM0-III) and Simplified Acute Physiology Score 3) was widely validated in different regions of the world and in distinct settings comprising general ICU patients as well as specific subgroups such as critically ill cancer patients, cardiovascular, surgical, acute kidney injury requiring renal replacement therapy and those in need of extra-corporeal membrane oxygen. Conflicting results are reported, and in general the scores presented a good discrimination despite a worse calibration as compared with the ones described in the original studies that generated them. Nonetheless, such calibration is often improved when customizations are performed both at ICU and region or country level.
  
  
  CONCLUSIONS
  ICU scoring systems provide a valuable framework to characterize patients' severity of illness for the evaluation of ICU performance, for quality improvement initiatives and for benchmarking purposes. However, to ensure the best accuracy, constant updates as well as regional customizations are required.
authors.affiliation: aD'Or Institute for Research and Education bPrograma de Pós-Graduação em Oncologia, Instituto Nacional de Câncer, Rio de Janeiro, Brazil.
authors.forename: Jorge I F
authors.initials: JI
authors.lastname: Salluh
authors.forename: Márcio
authors.initials: M
authors.lastname: Soares
mesh_terms: D018806:APACHE; D019985:Benchmarking; D016638:Critical Illness / Q000401:mortality; D017052:Hospital Mortality / Q000639:trends; D006801:Humans; D007362:Intensive Care Units / Q000592:standards*; D015233:Models, Statistical; D012720:Severity of Illness Index; D018434:Sickness Impact Profile; D016019:Survival Analysis