title: High volume and outcome after liver resection: surgeon or center?
abstract: BACKGROUND
  In a case controlled analysis, we attempted to determine if the volume-survival benefit persists in liver resection (LR) after eliminating differences in background characteristics.
  
  
  METHODS
  Using the Nationwide Inpatient Sample (NIS), we identified all LR (n = 2,949) with available surgeon/hospital identifiers performed from 1998-2005. Propensity scoring adjusted for background characteristics. Volume cut-points were selected to create equal groups. A logistic regression for mortality was then performed with these matched groups.
  
  
  RESULTS
  At high volume (HV) hospitals, patients (n = 1423) were more often older, white, private insurance holders, elective admissions, carriers of a malignant diagnosis, and high income residents (p < 0.05). Propensity matching eliminated differences in background characteristics. Adjusted in-hospital mortality was significantly lower in the HV group (2.6% vs. 4.8%, p = 0.02). Logistic regression found that private insurance and elective admission type decreased mortality; preoperative comorbidity increased mortality. Only LR performed by HV surgeons at HV centers was independently associated with improved in-hospital mortality (HR, 0.43; 95% CI, 0.22-0.83).
  
  
  CONCLUSIONS
  A socioeconomic bias may exist at HV centers. When these factors are accounted for and adjusted, center volume does not appear to influence in-hospital mortality unless LR is performed by HV surgeons at HV centers.
authors.affiliation: Department of Surgery, Surgical Outcomes Analysis & Research, University of Massachusetts Medical School, Worcester, MA 01655, USA.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Eppsteiner
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: Csikesz
authors.forename: Jessica P
authors.initials: JP
authors.lastname: Simons
authors.forename: Jennifer F
authors.initials: JF
authors.lastname: Tseng
authors.forename: Shimul A
authors.initials: SA
authors.lastname: Shah
mesh_terms: D016022:Case-Control Studies; D005260:Female; D013502:General Surgery / Q000706:statistics & numerical data*; D006498:Hepatectomy / Q000401:mortality / Q000706:statistics & numerical data*; D006761:Hospitals / Q000706:statistics & numerical data*; D006801:Humans; D008107:Liver Diseases / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010820:Physicians / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D016896:Treatment Outcome