Many states have recently changed regulations to allow physician assistants to work more collaboratively with physicians in team-based care. New Mexico and Tennessee have changed regulations to refer to "collaboration" rather than physician "supervision" of physician assistants. Thirty-eight states and the District of Columbia now allow scope of practice to be determined at the doctor's practice site. Many of the changes are in response to a shift to a team-based approach to healthcare delivery. More than 40 states have also implemented full prescriptive authority to physician assistants.