title: In-hospital vs. 30-day mortality in the critically ill - a 2-year Swedish intensive care cohort analysis.
abstract: BACKGROUND
  Standardised mortality ratio (SMR) is a common quality indicator in critical care and is the ratio between observed mortality and expected mortality. Typically, in-hospital mortality is used to derive SMR, but the use of a time-fixed, more objective, end-point has been advocated. This study aimed to determine the relationship between in-hospital mortality and 30-day mortality on a comprehensive Swedish intensive care cohort.
  
  
  METHODS
  A retrospective study on patients >15 years old, from the Swedish Intensive Care Register (SIR), where intensive care unit (ICU) admissions in 2009-2010 were matched with the corresponding hospital admissions in the Swedish Hospital Discharge Register. Recalibrated SAPS (Simplified Acute Physiology Score) 3 models were developed to predict and compare in-hospital and 30-day mortality. SMR based on in-hospital mortality and on 30-day mortality were compared between ICUs and between groups with different case-mixes, discharge destinations and length of hospital stays.
  
  
  RESULTS
  Sixty-five ICUs with 48861 patients, of which 35610 were SAPS 3 scored, were included. Thirty-day mortality (17%) was higher than in-hospital mortality (14%). The SMR based on 30-day mortality and that based on in-hospital mortality differed significantly in 7/53 ICUs, for patients with sepsis, for elective surgery-admissions and in groups categorised according to discharge destination and hospital length of stay.
  
  
  CONCLUSIONS
  Choice of mortality end-point influences SMR. The extent of the influence depends on hospital-, ICU- and patient cohort characteristics as well as inter-hospital transfer rates, as all these factors influence the difference between SMR based on 30-day mortality and SMR based on in-hospital mortality.
authors.affiliation: Department of Anaesthesiology and Intensive Care, Akershus University Hospital, Lørenskog, Norway.
authors.forename: K
authors.initials: K
authors.lastname: Rydenfelt
authors.affiliation: Department of Anaesthesiology and Intensive Care, Vrinnevi Hospital, Norrköping, Sweden.|Department of Cardiothoracic Anaesthesia and Intensive Care, Linköping University Hospital, Linköping, Sweden.|Department of Medical and Health Sciences, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Engerström
authors.affiliation: Department of Cardiothoracic Anaesthesia and Intensive Care, Linköping University Hospital, Linköping, Sweden.|Department of Medical and Health Sciences, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Walther
authors.affiliation: Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden.|The Burn Centre, Department of Hand, Plastic Surgery and Intensive Care, Linköping County Council, Linköping, Sweden.
authors.forename: F
authors.initials: F
authors.lastname: Sjöberg
authors.affiliation: Department of Research, Development and Education, Halland Hospital, Halmstad, Sweden.
authors.forename: U
authors.initials: U
authors.lastname: Strömberg
authors.affiliation: Department of Intensive and Perioperative Care, Skåne University Hospital, Malmö/Lund, Sweden.|Department of Anesthesiology and Intensive Care, Halland Hospital, Halmstad, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Samuelsson
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003422:Critical Care; D016638:Critical Illness / Q000401:mortality*; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D012042:Registries / Q000706:statistics & numerical data; D012189:Retrospective Studies; D013548:Sweden / Q000453:epidemiology