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Comparative Study
. 2014 Oct;52(10):926-31.
doi: 10.1097/MLR.0000000000000213.

Ambulatory surgery centers and outpatient procedure use among Medicare beneficiaries

Brent K Hollenbeck  1 , Rodney L Dunn, Anne M Suskind, Yun Zhang, John M Hollingsworth, John D Birkmeyer
Affiliations
Comparative Study

Ambulatory surgery centers and outpatient procedure use among Medicare beneficiaries

Brent K Hollenbeck et al. Med Care. 2014 Oct.

Abstract

Background: There has been a strong push to move outpatient surgery from hospital settings to ambulatory surgery centers (ASCs). Despite the efficiency advantages of ASCs, many are concerned that these facilities could increase overall utilization.

Objective: To assess the impact of ASC opening on rates of outpatient surgery.

Design: This was a retrospective cohort study of Medicare beneficiaries undergoing outpatient surgery between 2001 and 2010. We compared population-based rates of outpatient surgery in Hospital Service Areas (HSAs) with freestanding ASCs to those without. After adjusting for differences using multiple propensity score methods, we assessed the impact of ASC opening in an HSA previously without one on rates of outpatient surgery.

Subjects: Patients included were Medicare beneficiaries with Part B eligibility.

Main outcome measure: Adjusted HSA-level rates of outpatient surgery.

Results: Adjusted outpatient surgery rates increased from 2806 to 3940 per 10,000 and the number of ASC operating rooms grew from 7036 to 11,223 (both P<0.001 for trend). By the fourth year after opening, rates of outpatient surgery increased by 10.9% (from 3338 to 3701 per 10,000) in HSAs adding an ASC for the first time. In contrast, outpatient surgery rates grew by only 2.4% and 0.6% in HSAs where an ASC was always or never present, respectively (P<0.001 for test between 3 slopes).

Conclusions: Rather than redistributing patients from one setting to another, the opening of ASCs increases outpatient surgery use. However, the 10.9% increase is more modest than previously suggested by state-level data.

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Figures

Figure 1
Figure 1. Trends in adjusted rates of outpatient surgery and number of ASC operating rooms in the U.S.
Adjusted rates of outpatient surgery and number of ASC operating rooms were assessed over time. (p < 0.001 for trend over time for both).
Figure 2
Figure 2. Annual adjusted rates of outpatient surgery in markets with and without ASCs
Adjusted rates of outpatient surgery in HSAs with and without ASCs were contrasted for each year (p < 0.001 for every year).
Figure 3
Figure 3. Adjusted rates of outpatient surgery in HSAs where ASCs were always present, never present, and in those where an ASC opened for the first time
In the period prior to baseline, the rate of change in outpatient surgery across the three HSA groups was similar (p = 0.79). However, for the 4-year period following baseline, rates of outpatient surgery grew more rapidly in HSAs where an ASC was added for the first time (p < 0.001 for change over time relative to HSAs always with and without ASCs).
Figure 4
Figure 4. Adjusted rates of ophthalmologic (a), gastrointestinal (b) and musculoskeletal (c) outpatient surgery according to HSA grouping
In the period after baseline, adjusted rates of outpatient surgery experienced faster growth in HSAs where an ASC opened for the first time compared to HSAs in which an ASC was never present (p < 0.001 for all three specialty groups).
Figure 4
Figure 4. Adjusted rates of ophthalmologic (a), gastrointestinal (b) and musculoskeletal (c) outpatient surgery according to HSA grouping
In the period after baseline, adjusted rates of outpatient surgery experienced faster growth in HSAs where an ASC opened for the first time compared to HSAs in which an ASC was never present (p < 0.001 for all three specialty groups).
Figure 4
Figure 4. Adjusted rates of ophthalmologic (a), gastrointestinal (b) and musculoskeletal (c) outpatient surgery according to HSA grouping
In the period after baseline, adjusted rates of outpatient surgery experienced faster growth in HSAs where an ASC opened for the first time compared to HSAs in which an ASC was never present (p < 0.001 for all three specialty groups).
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References

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    1. MedPAC. Medicare Payment Policy 2013. Report to the Congress. [Accessed November 7, 2013]; Available at: http://www.medpac.gov/documents/Mar13_EntireReport.pdf.
    1. Centers for Medicare and Medicaid Services. Calendar year 2008 revised ambulatory surgical center payment system. [Accessed October 13, 2013]; Available at: http://www.cms.gov/Medicare/Medicare-Fee-for-Service-Payment/ASCPayment/....
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