Orthopedic Coding Alert

Question: When should I append modifier AS to a CPT code?

Kansas subscriber

Answer: If a nonphysician practitioner (NPP) serves as an assistant surgeon, you must use modifier AS (Physician assistant, nurse practitioner or clinical nurse specialist services for assistant at surgery) on your claims for Medicare payers.

Specifically, Medicare payers will typically reimburse for the services of a clinical nurse specialist (CNS), physician assistant (PA) and nurse practitioner (NP) as assistants at surgery, who "actively assist when a physician performs a Medicare-covered surgical procedure. This necessarily entails that the assistant be involved in the actual performance of the procedure, not simply in other, ancillary services" (Internet Only Manual, chapter 20, section 20.4.3).

Medicare will not reimburse for surgical assistants such as registered nurse first assists, licensed practical nurses, and certified surgical technologists. Medicare also will not reimburse for "orthopedic physician assistants" -- a physician extender credential that differs from the "physician assistant" credential in training and scope of practice.

Example: A PA assists the surgeon during shoulder arthroscopy that merits 29824 (Arthroscopy, shoulder, surgical; distal claviculectomy including distal articular surface [Mumford procedure]). The physician fee schedule (http://www.cms.hhs.gov/pfslookup/) assigns a "2" to the ASST SURG column for 29824, which means you may report an assistant at surgery for this procedure.

In this case, the surgeon would report 29824, and the PA will report 29824-AS.

Important: For Medicare, the PA assisting at surgery must have a Medicare (or Medicaid) provider number to bill for assistant-at-surgery services.