Geographic variation in the provider of screening colonoscopy in Canada: a population-based cohort study

BACKGROUND: Screening colonoscopy for the detection of colorectal carcinoma is provided by several specialties. Few studies have assessed geographic variation in the delivery of this care. Our objective was to investigate how geographic and socioeconomic factors affect who provides screening colonoscopy in Canada. METHODS: This was a population-based cohort of all screening colonoscopy procedures performed at publicly funded Canadian health care facilities (excluding those in Quebec) between April 2008 and March 2015. The main outcome of interest was the proportion of colonoscopy procedures performed by surgeons versus gastroenterologists at the neighbourhood level. Predictors of interest included socioeconomic and geographic variables. We used spatial analysis to evaluate significant clustering of practitioner services and multinomial logistic regression to model predictors. RESULTS: We identified 658 113 screening colonoscopy procedures performed by 1886 providers (1169 surgeons and 717 gastroenterologists) over the study period, of which 353 165 (53.7%) were performed by surgeons. A total of 24.2% of neighbourhoods were located within clusters predominantly served by gastroenterologists, and 19.5% were within surgeon clusters; the remainder were in mixed clusters. Rural neighbourhoods had a significantly increased relative risk of being within a surgeon cluster (relative risk [RR] 5.38, 95% confidence interval [CI] 3.48-8.01) compared to mixed clusters and nearly 100 times higher relative risk of being in a surgeon cluster compared to gastroenterologist clusters (RR 98.95, 95% CI 15.3-427.2). Neighbourhoods with the highest socioeconomic status were 1.74 (95% CI 1.14-2.56) times likelier to be in gastroenterologist clusters than in mixed clusters. INTERPRETATION: Surgeons provide a large proportion of colonoscopy procedures in Canada and are essential for access to care, particularly in rural regions. Most Canadians are served relatively equally by surgeons and gastroenterologists. This emphasizes the importance of both specialties to the delivery of colonoscopy care across the country.