MedPAC will test how new ASCs change outpatient surgical volume

MedPAC staff Alex Harris and Dan Zabinski presented a two-study workplan on ambulatory surgical centers to the Commission on September 3 — no findings yet, just what the Commission plans to measure and how.

The first study asks why ASC supply varies so much by geography: many markets have no ASCs at all, and MedPAC’s slides note beneficiaries there “lack access to the benefits of ASCs.” The design combines semi-structured interviews at ASC site visits across specialties, states, and market density with a cross-sectional regression on ASCs per capita at the health-service-area level, run against population characteristics (urbanicity, dual-eligibility share, social risk), surgical need and capacity (procedures and operating rooms per capita), the ASC/hospital-outpatient volume split, certificate-of-need status, and state medical-liability exposure. MedPAC also includes how outpatient surgical procedures are concentrated between ASCs and hospital outpatient departments.

The second study is the one with payment-policy teeth. MedPAC’s context slide gives two possible effects of ASC growth: it “could cause surgical procedures to shift from ASCs to HOPDs” — meaning hospital outpatient departments — or “could increase overall outpatient surgical volume.” Read literally, the first is backwards: a new ASC opening in a market would be expected to pull procedures the other way, out of hospital outpatient departments. The wording is not a slide typo alone — MedPAC staff read the same direction aloud at the meeting, adding “particularly for routine and high-volume procedures,” per the September 2026 meeting transcript. Either way the study measures the same thing — where outpatient surgery ends up after entry — and MedPAC proposes to settle it empirically with a staggered-adoption difference-in-differences design, comparing outpatient surgical volume in a market before and after a new ASC opens there. Primary outcomes, tracked in both ASCs and hospital outpatient departments, are total hip and knee arthroplasty, cataract removal, and diagnostic colonoscopy; secondary outcomes, which also cover physician offices, are cystoscopy, trigger-finger and carpal-tunnel release, and epidural steroid injections.

MedPAC’s own slides describe the existing research on both questions as “somewhat limited and dated.” The Commission’s discussion slide says only that it will take feedback on the workplan and present analytic results at a future meeting — no timeline is given. Nothing here is a finding: it is a methodology, and the volume study’s answer, whenever it lands, is the one worth watching. A result showing ASC entry mostly adds volume rather than moving it between settings would cut against the sector’s cost-savings case.

Correction, Sept. 11, 2026: An earlier version’s headline, summary and closing described MedPAC’s second study as testing whether new ASCs pull surgery out of hospital outpatient departments. MedPAC’s slide and its staff presentation both describe the possible shift as running the other way, from ASCs to HOPDs. This version reports MedPAC’s wording and notes the discrepancy.