What does PHDPA C mean when used behind a persons name in the medical field?

PHDPA-C stands for Doctor of Public Health, Physician Assistant-Certified. It is a credential used in the United States to denote a physician assistant who has met the requirements of the Physician Assistant Education Association and has been certified by the National Commission on Certification of Physician Assistants. PA-Cs practice medicine under the supervision of a physician and often work in primary care settings.