Depends on the insurance...
Regardless of insurance it would be one code, but if it's Medicare (or a payer that follows Medicare) who it was billed under depends on whether or not "incident to" requirements are met:
(from CMS)
http://www.cms.gov/manuals/downloads/clm104c12.pdf
Office/Clinic Setting
In the office/clinic setting when the physician performs the E/M service the service must be reported using the physician‟s UPIN/PIN. When an E/M service is a shared/split encounter between a physician and a non-physician practitioner (NP, PA, CNS or CNM), the service is considered to have been performed “incident to” if the requirements for “incident to” are met and the patient is an established patient. If “incident to” requirements are not met for the shared/split E/M service, the service must be billed under the NPP‟s UPIN/PIN, and payment will be made at the appropriate physician fee schedule payment.
(from AAD)
http://www.aad.org/pm/billing/medicare/_doc/FAQonIncidentToBilling.pdf
Incident to requirements:
To bill Medicare "incident to" for services provided by an NPP the following criteria must be met:
• The service performed must be one that is typically performed in a physician's office.
• The service performed should be within the scope of practice of the NPP and in accordance with state
law.
• The physician must personally treat the patient on the patient's first visit to the practice or treat any
established patient who comes to the office with a new medical condition. NPPs may provide follow-up
care.
• The physician must be in the suite of offices (on-site) when the NPP is rendering the service.