You can't bill Medicare directly for technical components of diagnostic procedures provided for SNF patients, even if done in the physician's office. You must bill Part A through the SNF under PPS. In order to be paid, your practice must bill the SNF and have a prearranged agreement that the SNF will pay the physician.
Once the patient exhausts his Part A benefits (having been at the SNF for more than 100 days following the hospital visit) or if he fails to meet CMS- Part A level-of-care requirements, the patient is in a Part B stay as a nursing facility patient and services aren't subject to consolidated billing. You should be able to bill Medicare directly for all components of diagnostic testing, as long as you have a physician order and medical necessity.