title: Anastomotic leakage as an outcome measure for quality of colorectal cancer surgery.
abstract: BACKGROUND
  When comparing mortality rates between hospitals to explore hospital performance, there is an important role for adjustment for differences in case-mix. Identifying outcome measures that are less influenced by differences in case-mix may be valuable. The main goal of this study was to explore whether hospital differences in anastomotic leakage (AL) and postoperative mortality are due to differences in case-mix or to differences in treatment factors.
  
  
  METHODS
  Data of the Dutch Surgical Colorectal Audit were used. Case-mix factors and treatment-related factors were identified from the literature and their association with AL and mortality were analysed with logistic regression. Hospital differences in observed AL and mortality rates, and adjusted rates based on the logistic regression models were shown. The reduction in hospital variance after adjustment was analysed with Levene's test for equality of variances.
  
  
  RESULTS
  17 of 22 case-mix factors and 4 of 11 treatment factors related to AL derived from the literature were available in the database. Variation in observed AL rates between hospitals was large with a maximum rate of 17%. This variation could not be attributed to differences in case-mix but more to differences in treatment factors. Hospital variation in observed mortality rates was significantly reduced after adjustment for differences in case-mix.
  
  
  CONCLUSIONS
  Hospital variation in AL is relatively independent of differences in case-mix. In contrast to 'postoperative mortality' the observed AL rates of hospitals evaluated in our study were only slightly affected after adjustment for case-mix factors. Therefore, AL rates may be suitable as an outcome indicator for measurement of surgical quality of care.
authors.affiliation: Department of Surgery, Leiden University Medical Centre, Leiden, The Netherlands. h.s.snijders@lumc.nl
authors.forename: H S
authors.initials: HS
authors.lastname: Snijders
authors.forename: D
authors.initials: D
authors.lastname: Henneman
authors.forename: N L
authors.initials: NL
authors.lastname: van Leersum
authors.forename: M
authors.initials: M
authors.lastname: ten Berge
authors.forename: M
authors.initials: M
authors.lastname: Fiocco
authors.forename: T M
authors.initials: TM
authors.lastname: Karsten
authors.forename: K
authors.initials: K
authors.lastname: Havenga
authors.forename: T
authors.initials: T
authors.lastname: Wiggers
authors.forename: J W
authors.initials: JW
authors.lastname: Dekker
authors.forename: R A E M
authors.initials: RA
authors.lastname: Tollenaar
authors.forename: M W J M
authors.initials: MW
authors.lastname: Wouters
mesh_terms: D000714:Anastomosis, Surgical / Q000592:standards*; D057868:Anastomotic Leak / Q000209:etiology / Q000401:mortality; D015179:Colorectal Neoplasms / Q000601:surgery*; D016001:Confidence Intervals; D003953:Diagnosis-Related Groups; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008485:Medical Audit; D016017:Odds Ratio; D017063:Outcome Assessment, Health Care; D011446:Prospective Studies; D019984:Quality Indicators, Health Care; D012307:Risk Factors
keywords: Audit and feedback; Mortality (standardized mortality ratios); Quality measurement; Surgery