Because of the close working relationship the PAs have with physicians, PAs are educated in the medical model designed to complement physician training. Upon graduation, physician assistants take a national certification examination developed by the National Commission on Certification of PAs in conjunction with the National Board of Medical Examiners. To maintain their national certification, PAs must log 100 hours of continuing medical education every two years and sit for a recertification every six years. Graduation from an accredited physician assistant program and passage of the national certifying exam are required for state licensure.