When a non-physician practitioner (NPP) performs an incident to service, that NPP must follow the plan of care as prescribed. He or she may not independently change the course of treatment. This requirement appears in Chapter 15, Section 60 of the Medicare Benefit Policy Manual, as shown in bold text:

… to have …[a] service covered as incident to the services of a physician, it must be performed under the direct supervision of the physician as an integral part of the physician’s personal in-office service. As explained in §60.1, this does not mean that each occasion of an incidental service performed by a nonphysician practitioner must always be the occasion of a service actually rendered by the physician. It does mean that there must have been a direct, personal, professional service furnished by the physician to initiate the course of treatment of which the service being performed by the nonphysician practitioner is an incidental part, and there must be subsequent services by the physician of a frequency that reflects the physician’s continuing active participation in and management of the course of treatment. In addition, the physician must be physically present in the same office suite and be immediately available to render assistance if that becomes necessary.

There may be changes in the course of treatment, over time, but a physician (not the nonphysician practitioner billing incident to) is required to make those changes.