The guidelines don't specifically mention which parts of the visit must be performed by the billing provider (physician or NPP). Instead, CMS has indicated that the work described in the guidelines should be understood as physician (or NPP) work except when specific allowance is made otherwise.
Specific allowance is made for individuals other than the billing provider to obtain and document the ROS and PFSH subcomponents of History. In the '97 guidelines, allowance is made for ancillary staff to obtain and document the vitals (with virtually all Medicare carriers allowing this when '95 guidelines are used as well).
This is mentioned in the 10/24/05 Part B News, where it says:
"The entire set of guidelines were written to identify the physician work [emphasis added] necessary to perform and document" the medical record for an E/M service, an E/M guru from CMS tells Part B News. The official says those are - as Buechner points out - ROS, PFSH and vitals.
Medicare says that medical students are allowed to obtain ROS/PFSH only, but doesn't specifically mention allied health students. The usual understanding is that they, like medical students, are also limited to the ROS and/or PFSH portions of the encounter.