Physician Assistant A Physician Assistant (PA) is a health care professional licensed to conduct physical examinations, diagnose and treat illnesses, order and interpret diagnostic patient tests, assist in surgery, and write prescriptions for patient medications. The Physician Assistant is trained in the medical model designed to complement physician training. PAs are found in all areas of medicine including family medicine, internal medicine, pediatrics, obstetrics and gynecology, emergency medicine, and surgery. Brad Reiners, P.A.-C.