Outpatient Definitions and Methodology

Service Statistics

All information in this report is taken from the Medicare Outpatient Prospective Payment System (OPPS) Limited Data Set which is updated annually by CMS based on the calendar year.  The file includes billing data for 100% of all Medicare fee-for-service claims for hospital outpatient services during the twelve months ending December 31.  The report is based on the most recent period available and is consistent with CMS cell size suppression policy.

Services are defined based on the revenue code for a line item.  Averages are based on units of service (i.e. the number of units of items or services delivered).

  • Number Patient Claims - the total number of claims for the service.
  • Units of Service - the number of units of the items or services delivered.  (One claim may have multiple units of service for an item or service.)
  • Average Charge - the total charges (covered and non-covered) for all accommodations and services (related to the revenue code) for a billing period before reduction for the deductible and coinsurance amounts and before an adjustment for the cost of services provided.
  • Average Cost - Charges adjusted to cost using the hospital's specific cost center cost-to-charge ratio. This calculation is done by CMS and included with OPPS claims data. (Details of the calculation are not provided by CMS.)
  • Average Payment - The computed OPPS payment for a line item based on the payment APC. The "payment APC" refers to total payment, including deductible, coinsurance, and program payment.
  • Service Mix Index (SMI) - Each APC has a relative weight assigned by CMS. The Service Mix Index is the average relative weight of the procedures billed for a service (e.g. the average relative weight of all surgical procedures performed).