NHIA Reimbursement Training Center

Ambulatory Infusion Suites (AIS)

Many home infusion therapy providers also operate a health care facility called ambulatory infusion suite (AIS) of the home infusion therapy provider.  The AIS of the home infusion therapy provider is a setting where the clinical care provided pursuant to physician orders is managed and performed by RN’s and registered pharmacists that are highly skilled in provision of infusion/specialty drug administration.  National accrediting organizations (e.g., The Joint Commission) recognize these infusion suite settings as adjunct to the services of a home infusion therapy provider with supplemental accreditation standards.

This is one of three types of ambulatory infusion centers (AICs):


AIS Coding: The –SS modifier is also used with any of the HCPCS per diem “S” codes for home infusion therapy including infusion, injection and other administrations, Appending -SS therefore modifies the code descriptions to indicate the administration was provided in the AIS. 

For example, if infliximab is administered then in addition to coding for the nursing, the other services provided in the AIS would be coded with:

S9359-SS  Home infusion therapy, anti-tumor necrosis factor intravenous therapy; (e.g. infliximab); administrative services, professional pharmacy services, care coordination, and all necessary

You may also identify that the service took place in a AIS by using the place of service code 49 – Independent Clinic – “A location, not part of a hospital and not described by any other Place of Service code, that is organized and operated to provide preventive, diagnostic, therapeutic, rehabilitative, or palliative services to outpatients only.”

While Medicare does cover clinical services and infused drugs administered in the physician or hospital based infusion clinics they do NOT cover services provided in an AIS.


Physician-based infusion clinic: Since Medicare does not cover the clinical services or drugs infused in a AIS, some home infusion providers have added  medical services companies that are either physician based, or nurse practitioner based with medical director oversight.   In this model both Medicare and non-Medicare patients can be serviced once the physician and/or nurse practitioner has been credentialed by Medicare, Medicaid and commercial payers. 


Medicare patients must meet the criteria established by the A/B MAC Local Coverage Determinations (LCD).  The drugs and related services are billed to the A/B Medicare Administrative Contractors based on the Physician Fee Schedule, which is very different from per diem S-code billing. An example of drug administration HCPCS codes used in the physician-based clinic setting:


Hospital-based infusion clinic: As the name suggests hospital-based infusion clinics are hospital based outpatient clinics that provide infused drugs.  They use the same HCPCS codes set as the physician-based infusion clinics, but are paid at different rates.