Ambulatory Health Care Services

NAICS 621 covers outpatient health care providers — physician offices, dental practices, urgent-care clinics, ambulatory surgery centers (ASCs), home health agencies, diagnostic imaging labs, and physical therapy clinics. These establishments deliver care without overnight admission, and the subsector has grown as the US healthcare system shifts volume from hospitals (NAICS 622) to lower-cost outpatient settings. The Medicare Payment Advisory Commission (MedPAC) has tracked this migration for over a decade, noting that ASC procedure volume has risen while hospital outpatient department (HOPD) volumes for comparable procedures have plateaued.

The subsector's revenue model is dominated by third-party reimbursement. Medicare, Medicaid, and commercial insurers like UnitedHealthcare, Anthem (Elevance Health), and Aetna (CVS Health) set fee schedules that determine what providers earn per visit or procedure. CMS's Medicare Physician Fee Schedule (MPFS) and the Outpatient Prospective Payment System (OPPS) are the two most influential federal payment frameworks. The 2024 MPFS rule cut the conversion factor by 1.25%, continuing a multi-year trend of real-value declines that the AMA and specialty societies have lobbied Congress to address.

Private equity investment has reshaped ownership structures. PE-backed platforms like US Physical Therapy, Aspen Dental Management, and TeamHealth have acquired hundreds of physician practices and dental offices, particularly in dermatology, ophthalmology, gastroenterology, and emergency medicine. The FTC's 2023 scrutiny of PE roll-ups in healthcare — including investigations into price increases following acquisitions — represents a regulatory frontier specific to ambulatory-care consolidation. Geographic concentration varies by segment: urgent-care density is highest in suburban Sun Belt markets (Texas, Florida, Arizona), while home-health agencies cluster in states with older populations like Florida, Pennsylvania, and Ohio.