title: Association of severity of illness and intensive care unit readmission: A systematic review.
abstract: OBJECTIVE
  To determine whether ICU readmission is associated with higher severity of illness scores in adult patients.
  
  
  BACKGROUND
  Readmissions to the intensive care unit (ICU) are associated with increased costs, morbidity, and mortality.
  
  
  METHODS
  We performed searches of MEDLINE, EMBASE, and grey literature databases. We selected studies reporting data from adults who were hospitalized in an ICU, received severity of illness scores, and were discharged from the ICU. Characteristics of readmitted and non-readmitted patients were examined.
  
  
  RESULTS
  We screened 4766 publications and included 31 studies in our analysis. In most studies, severity of illness scores were higher in patients readmitted to the ICU. Readmission was also associated with higher mortality and longer ICU and hospital stays. Excessive heterogeneity precluded the reporting of results in the form of a meta-analysis.
  
  
  CONCLUSIONS
  ICU readmission is associated with higher severity of illness scores during the same hospitalization in adult patients.
authors.affiliation: Department of Surgery, McGill University, Montreal, Quebec, Canada; Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA. Electronic address: evan.wong@mail.mcgill.ca.
authors.forename: Evan G
authors.initials: EG
authors.lastname: Wong
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Ann M
authors.initials: AM
authors.lastname: Parker
authors.affiliation: The Hugo W. Moser Research Institute, Kennedy Krieger Institute, Baltimore, MD, USA; Department of Neurology, School of Medicine, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Doris G
authors.initials: DG
authors.lastname: Leung
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Emily P
authors.initials: EP
authors.lastname: Brigham
authors.affiliation: Division of Geriatric Medicine and Gerontology, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Alicia I
authors.initials: AI
authors.lastname: Arbaje
mesh_terms: D000328:Adult; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D007902:Length of Stay; D010351:Patient Discharge; D010359:Patient Readmission / Q000706:statistics & numerical data*
keywords: Intensive care unit; Outcomes; Readmission; Severity of illness; Systematic review