1. Method developed by the Centers for Medicare and Medicaid Services (CMS) for outpatient hospital reimbursement based on procedures that have similar clinical characteristics and similar costs rather than on diagnoses. 2. Medicare’s outpatient prospective payment system (OPPS) for hospital outpatient services that became effective August 1, 2000. Depending on the services given, hospital facilities may be paid for more than one APC for an encounter. APC information is updated and released twice a year in the Federal Register. Also called ambulatory payment classes, ambulatory patient classifications (APCs), and ambulatory patient care groups.

Operative procedure performed on a patient as an outpatient in which he or she is admitted, treated, and released on the same day from the facility. Also referred to as outpatient surgery.

ASCs were adopted to replace ambulatory patient groups (APGs) for outpatient or 1-day surgery cases that were derived from the surgery section of the CPT. Later, this was replaced by the ambulatory payment classification (APC) system.

Licensed freestanding facility, other than a physician’s office, at which outpatient medical services are provided on an ambulatory basis (e.g., diagnosis, treatment, same-day surgery, rehabilitation). ASCs are hospital based (or sponsored) or independently owned (or sponsored). Surgery of an uncomplicated nature that traditionally was done on an inpatient basis but can be performed with equal efficiency without hospital admission is now being done in an ASC. To receive payment for Medicare patients, the facility must have an agreement with the Centers for Medicare and Medicaid Services (CMS) and meet specific requirements. ASCs are paid according to nine different payment groups based only on their cost similarities. Also called surgicenter or ambulatory surgical center.

Facility’s schedule for the performance of elective surgical procedures on patients admitted and discharged on the same day the procedure is performed.

Evaluation and analysis of the medical necessity, appropriateness, and efficiency of medical services given in an ambulatory facility. Utilization review is typically performed by a utilization review committee.