Ambulatory surgery centers (ASCs) potentially deliver care more efficiently than hospitals. However, ASC proliferation may increase discretionary surgery use because of financial incentives for the physicians who staff them. To explore this possibility, we measured the impact of the opening of an ASC in a health care market, as defined by the hospital service area (HSA), on rates of procedure use.
With a 100% sample of outpatient surgery encounters, we measured annual rates of use for discretionary (cataract surgery, colonoscopy, and upper gastrointestinal [GI] tract endoscopy) and imperative (cancer-directed breast surgery) procedures among Medicare-eligible persons. Using a multiple time series research design, we compared the change in procedure use for HSAs where ASCs opened with that of HSAs where an ASC was never present.
All patients 65 years or older undergoing outpatient surgery from January 1, 1998, through December 31, 2006.
Main Outcome Measure
Adjusted HSA-level rates of procedure use.
In HSAs where an ASC opened, colonoscopy use increased by 1610 procedures per 100 000 per year (95% confidence interval, 736-2485; P < .001) and upper GI tract endoscopy use increased by 775 procedures per 100 000 per year (159-1391; P = .01). However, rates of cancer-directed breast surgery remained flat. Among HSAs where an ASC opened, the relative increases in colonoscopy and upper GI tract endoscopy use were approximately 117% and 93% higher, respectively, 4 years after the opening compared with HSAs without ASCs.
The opening of an ASC within an HSA is associated with significant increases in discretionary surgery use.