You cannot bill for the nurse visit under the provider who ordered the blood work because the nurse is not supervised by that physician. That physician isn't even aware that the nurse is seeing the patient, and will most likely not even see the notes from that visit. The nurse visit should be billed under the physician who supervises the nurse, and who the nurse is employed by. You are correct, you cannot bill for a provider under the group NPI if that provider isn't part of the group.
Michele