title: To what extent should quality of care decisions be based on health outcomes data? Application to carotid endarterectomy.
abstract: OBJECTIVE
  Most quality improvement methods implicitly assume that facilities with high complication rates are likely to have substandard processes of care, a stable characteristic that, in the absence of intervention, will persist over time. We assessed the extent to which this holds true for carotid endarterectomy.
  
  
  METHODS
  Using data from the Department of Veterans Affairs National Surgical Quality Improvement Project, we classified facilities on the basis of 30-day complications of carotid endarterectomy (stroke, myocardial infarction, death) during 1994 to 1995 (period 1, n=3389) and then compared these groups of facilities for complication rates during 1996 to 1997 (period 2, n=4453).
  
  
  RESULTS
  Despite wide variation in facility-specific complication rates, the correlation between rates in periods 1 and 2 was low (Spearman correlation coefficient, 0.04; P=0.01) Facility-specific rates did not show greater correlation when we examined only facilities with higher volumes patients in different clinical categories (asymptomatic, transient ischemic attack, stroke). Comorbid illness profiles were similar between the 2 time periods.
  
  
  CONCLUSIONS
  Most of the facility-specific differences in complication rates in period 1 were not maintained into period 2. Many apparent quality improvement problems may not be as large as they first appear, especially when based on few complications per facility. The inability, in practice, to estimate complication rates at a high degree of precision is a fundamental difficulty for clinical policy making regarding procedures with complication rates such as carotid endarterectomy.
authors.affiliation: Department of Biostatistics, Center for Clinical Health Policy, Division of General Internal Medicine, Duke University Medical Center, Durham, NC, USA.
authors.forename: Gregory
authors.initials: G
authors.lastname: Samsa
authors.forename: Eugene Z
authors.initials: EZ
authors.lastname: Oddone
authors.forename: Ronnie
authors.initials: R
authors.lastname: Horner
authors.forename: Jennifer
authors.initials: J
authors.lastname: Daley
authors.forename: William
authors.initials: W
authors.lastname: Henderson
authors.forename: David B
authors.initials: DB
authors.lastname: Matchar
mesh_terms: D000368:Aged; D002340:Carotid Artery Diseases / Q000453:epidemiology / Q000601:surgery; D015331:Cohort Studies; D003661:Decision Support Techniques; D003710:Demography; D016894:Endarterectomy, Carotid / Q000009:adverse effects* / Q000706:statistics & numerical data*; D005260:Female; D006787:Hospitals, Veterans / Q000592:standards*; D006801:Humans; D008297:Male; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data*; D011183:Postoperative Complications / Q000453:epidemiology; D011446:Prospective Studies; D019984:Quality Indicators, Health Care; D017749:Total Quality Management; D014481:United States