title: Hospital standardized mortality ratios: sensitivity analyses on the impact of coding.
abstract: BACKGROUND
  Hospital standardized mortality ratios (HSMRs) are derived from administrative databases and cover 80 percent of in-hospital deaths with adjustment for available case mix variables. They have been criticized for being sensitive to issues such as clinical coding but on the basis of limited quantitative evidence.
  
  
  METHODS
  In a set of sensitivity analyses, we compared regular HSMRs with HSMRs resulting from a variety of changes, such as a patient-based measure, not adjusting for comorbidity, not adjusting for palliative care, excluding unplanned zero-day stays ending in live discharge, and using more or fewer diagnoses.
  
  
  RESULTS
  Overall, regular and variant HSMRs were highly correlated (ρ>0.8), but differences of up to 10 points were common. Two hospitals were particularly affected when palliative care was excluded from the risk models. Excluding unplanned stays ending in same-day live discharge had the least impact despite their high frequency. The largest impacts were seen when capturing postdischarge deaths and using just five high-mortality diagnosis groups.
  
  
  CONCLUSIONS
  HSMRs in most hospitals changed by only small amounts from the various adjustment methods tried here, though small-to-medium changes were not uncommon. However, the position relative to funnel plot control limits could move in a significant minority even with modest changes in the HSMR.
authors.affiliation: Department of Primary Care and PublicHealth, Imperial College London, 12 Smithfield St., London EC1A 9LA, UK. robert.bottle@imperial.ac
authors.forename: Alex
authors.initials: A
authors.lastname: Bottle
authors.forename: Brian
authors.initials: B
authors.lastname: Jarman
authors.forename: Paul
authors.initials: P
authors.lastname: Aylin
mesh_terms: D000367:Age Factors; D059019:Clinical Coding / Q000706:statistics & numerical data*; D015897:Comorbidity; D006739:Hospital Administration / Q000706:statistics & numerical data*; D017052:Hospital Mortality; D006801:Humans; D009026:Mortality; D010166:Palliative Care / Q000706:statistics & numerical data; D019984:Quality Indicators, Health Care / Q000706:statistics & numerical data*; D020379:Risk Adjustment