Teaching Hospital Status and Operative Mortality in the United States Tipping Point in the Volume-Outcome Relationship Following Colon Resections?

Objective: To compare risk- and volume-adjusted outcomes of colon resections performed at teaching hospitals (THs) vs non-THs to assess whether benign disease may influence the volume-outcome effect. Design: Retrospective data analysis examining colon resections determined by International Classification of Diseases, Ninth Revision, Clinical Modification classification performed in the United States from 2001 through 2005 using the Nationwide Inpatient Sample (NIS) and the Area Resource File (2004). Patient covariates used in adjustment included age, sex, race, Charlson Index comorbidity score, and insurance status. Hospital covariates included TH status, presence of a colorectal surgery fellowship approved by the Accreditation Council for Graduate Medical Education, geographical region, institutional volume, and urban vs rural location. Countyspecific surgeon characteristics used in adjustment included average age of surgeons and proportion of colorectal board-certified surgeons within each county. Environmental or county covariates included median income and percentage of county residents living below the federal poverty level. Setting: A total of 1045 hospitals located in 38 states in the United States that were included in the NIS. Patients: All patients older than 18 years who had colon resection and were discharged from a hospital included in the NIS. Main Outcome Measures: Operative mortality, length of stay (LOS), and total charges. Results: A total of 115 250 patients were identified, of whom 4371 died (3.8%). The mean LOS was 10 days. Fewer patients underwent surgical resection in THs than in non- THs (46 656 vs 68 589). Teaching hospitals were associated with increased odds of death (odds ratio, 1.14) (P=.03), increased LOS (P=.003), and a nonsignificant trend toward an increase in total charges (P=.36). Conclusions: With the inclusion of benign disease, colon surgery displays a volume-outcome relationship in favor of non-THs. Inclusion of benign disease may represent a tipping point.