title: Including post-discharge mortality in calculation of hospital standardised mortality ratios: retrospective analysis of hospital episode statistics.
abstract: OBJECTIVE
  To assess the consequences of applying different mortality timeframes on standardised mortality ratios of individual hospitals and, secondarily, to evaluate the association between in-hospital standardised mortality ratios and early post-discharge mortality rate, length of hospital stay, and transfer rate.
  
  
  METHODS
  Retrospective analysis of routinely collected hospital data to compare observed deaths in 50 diagnostic categories with deaths predicted by a case mix adjustment method.
  
  
  METHODS
  60 Dutch hospitals.
  
  
  METHODS
  1 228 815 patients discharged in the period 2008 to 2010.
  
  
  METHODS
  In-hospital standardised mortality ratio, 30 days post-admission standardised mortality ratio, and 30 days post-discharge standardised mortality ratio.
  
  
  RESULTS
  Compared with the in-hospital standardised mortality ratio, 33% of the hospitals were categorised differently with the 30 days post-admission standardised mortality ratio and 22% were categorised differently with the 30 days post-discharge standardised mortality ratio. A positive association was found between in-hospital standardised mortality ratio and length of hospital stay (Pearson correlation coefficient 0.33; P=0.01), and an inverse association was found between in-hospital standardised mortality ratio and early post-discharge mortality (Pearson correlation coefficient -0.37; P=0.004).
  
  
  CONCLUSIONS
  Applying different mortality timeframes resulted in differences in standardised mortality ratios and differences in judgment regarding the performance of individual hospitals. Furthermore, associations between in-hospital standardised mortality rates, length of stay, and early post-discharge mortality rates were found. Combining these findings suggests that standardised mortality ratios based on in-hospital mortality are subject to so-called "discharge bias." Hence, early post-discharge mortality should be included in the calculation of standardised mortality ratios.
authors.affiliation: Department of Anesthesiology, University Medical Center Utrecht, Heidelberglaan 100, PO Box 85500, 3508 GA Utrecht, Netherlands.
authors.forename: Maurice E
authors.initials: ME
authors.lastname: Pouw
authors.forename: L M
authors.initials: LM
authors.lastname: Peelen
authors.forename: K G M
authors.initials: KG
authors.lastname: Moons
authors.forename: C J
authors.initials: CJ
authors.lastname: Kalkman
authors.forename: H F
authors.initials: HF
authors.lastname: Lingsma
mesh_terms: D019985:Benchmarking / Q000379:methods*; D016208:Databases, Factual; D005260:Female; D017052:Hospital Mortality; D006761:Hospitals / Q000592:standards*; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D010351:Patient Discharge; D010360:Patient Transfer / Q000706:statistics & numerical data; D012042:Registries; D012189:Retrospective Studies; D020379:Risk Adjustment; D013997:Time Factors