or
(iii) Be a registered professional nurse who is authorized by the State in which the services are furnished to practice as a nurse practitioner in accordance with State law and have been granted a Medicare billing number as a nurse practitioner by December 31, 2000; or (iv) Be a nurse practitioner who on or after January 1, 2001, applies for a Medicare billing number for the first time and meets the standards for nurse practitioners in paragraphs (c)(8)(i) and (c)(8)(ii) of this section; or (v) Be a nurse practitioner who on or after January 1, 2003, applies for a Medicare billing number for the first time and possesses a master's degree in nursing and meets the standards for nurse practitioners in paragraphs (b)(1)(i) and (b)(1)(ii) of this section. (9) A clinical nurse specialist is a person who must: (i) Be a registered nurse who is currently licensed to practice in the State where he or she practices and be authorized to perform the services of a clinical nurse specialist in accordance with State law; (ii) Have a master's degree in a defined clinical area of nursing from an accredited educational institution; and, (iii) Be certified as a clinical nurse specialist by the American Nurses Credentialing Center. (10) A physician assistant is a person who: (i) Has graduated from a physician assistant educational program that is accredited by the Commission on Accreditation of Allied Health Education Programs; or (ii) Has passed the national certification examination that is administered by the National Commission on Certification of Physician Assistants; and (iii) Is licensed by the State to practice as a physician assistant.