Whether or not an assistant surgeon is allowed is determined by the Medicare Physician Fee Schedule Data Base. All surgical procedures have an indicator in the Medicare Fee Schedule that tells whether or not an assistant surgeon is allowed. There are four indicators.  

Zero = Payment restriction for assistant at surgery applies to this procedure unless  supporting documentation is submitted to establish medical necessity.

One = Statutory payment restriction for assistants at surgery applies to this procedure. Assistant at surgery may not be paid.

Two = Payment restriction for assistants at surgery does not apply to this procedure. Assistant at surgery may be paid.

Nine = Concept does not apply.

When looking in the Medicare Fee Schedule, services with a two indicator are allowed to be paid an assistant surgeon.

There are four modifiers to use for an assistant surgeon.

Modifier 80 is for an assistant surgeon.

Modifier 81 a minimum assistant surgeon.

Modifier 82 an assistant surgeon when qualified resident surgeon is not available. This modifier is used in teaching facilities to indicate that a resident who normally would be providing the assistant surgeon services was not available.

AS is an HCPCS modifier to indicate that a physician assistant, nurse practitioner, or clinical nurse specialist services were used for an assistant surgeon when the patient has Medicare.

It is not permissible for a practice to bill the patient for assistant surgeon services when that service is not allowed by Medicare.  Practices should check the Medicare Physician Fee Schedule Database to see if an assistant at surgeon is allowed. When a Non-Physician Practitioner (NPP) provides this service on a Medicare patient, use modifier AS.