title: Reliability of hospital readmission rates in vascular surgery.
abstract: OBJECTIVE
  The Center for Medicare and Medicaid Services recently began assessing financial penalties to hospitals with high readmission rates for a narrow set of medical conditions. Because these penalties will be extended to surgical conditions in the near future, we sought to determine whether readmissions are a reliable predictor of hospital performance with vascular surgery.
  
  
  METHODS
  We examined 4 years of national Medicare claims data from 1576 hospitals on beneficiaries undergoing three common vascular procedures: open or endovascular abdominal aortic aneurysm repair (n = 81,520) or lower extremity arterial bypass (n = 57,190). First, we divided our population into two groups on the basis of operative date (2005-2006 and 2007-2008) and generated hospital risk- and reliability-adjusted readmission rates for each time period. We evaluated reliability through the use of the "test-retest" method; highly reliable measures will show little variation in rates over time. Specifically, we evaluated the year-to-year reliability of readmissions by calculating Spearman rank correlation and weighted κ tests for readmission rates between the two time periods.
  
  
  RESULTS
  The Spearman coefficient between 2005-2006 readmissions rankings and 2007-2008 readmissions rankings was 0.57 (P < .001) and weighted κ was 0.42 (P < .001), indicating a moderate correlation. However, only 32% of the variation in hospital readmission rates in 2007-2008 was explained by readmissions during the 2 prior years. There were major reclassifications of hospital rankings between years, with 63% of hospitals migrating among performance quintiles between 2005-2006 and 2007-2008.
  
  
  CONCLUSIONS
  Risk-adjusted readmission rates for vascular surgery vary substantially year to year; this implies that much of the observed variation in readmission rates is either random or caused by unmeasured factors and not caused by changes in hospital quality that may be captured by administrative data.
authors.affiliation: Department of Surgery, Center for Healthcare Outcomes and Policy (CHOP), University of Michigan, Ann Arbor, Mich; Department of Surgery, University of Illinois Hospital and Health Sciences System, Chicago, Ill. Electronic address: aagonzal@umich.edu.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Gonzalez
authors.affiliation: Department of Surgery, Center for Healthcare Outcomes and Policy (CHOP), University of Michigan, Ann Arbor, Mich.
authors.forename: Micah E
authors.initials: ME
authors.lastname: Girotti
authors.affiliation: Department of Surgery, Center for Healthcare Outcomes and Policy (CHOP), University of Michigan, Ann Arbor, Mich.
authors.forename: Terry
authors.initials: T
authors.lastname: Shih
authors.affiliation: Section of Vascular Surgery, University of Michigan, Ann Arbor, Mich.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Wakefield
authors.affiliation: Department of Surgery, Center for Healthcare Outcomes and Policy (CHOP), University of Michigan, Ann Arbor, Mich.
authors.forename: Justin B
authors.initials: JB
authors.lastname: Dimick
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D017722:Hospital Charges; D006801:Humans; D015994:Incidence; D008297:Male; D006278:Medicare / Q000706:statistics & numerical data; D010359:Patient Readmission / Q000191:economics / Q000706:statistics & numerical data*; D011183:Postoperative Complications / Q000191:economics / Q000453:epidemiology* / Q000601:surgery; D015203:Reproducibility of Results; D014481:United States / Q000453:epidemiology; D014652:Vascular Diseases / Q000191:economics / Q000601:surgery*; D014656:Vascular Surgical Procedures