Health care professional academically, clinically prepared, and licensed to practice medicine with supervision and guidance of a licensed doctor of medicine or osteopathy. Depending on state laws, PAs perform the following: take medical histories, diagnose and treat conditions, order and interpret laboratory tests, perform physical examinations, assist in surgery, counsel patients, and prescribe, administer, and dispense medications. Training programs average 25 to 27 months. National certification is available to graduates of approved training programs, a master’s-degree level in most states. Also referred to as a physician extender (PE).