20 CFR § 335.3 - Execution of statement of sickness and supplemental doctor's statement.
(a) Who may execute. A statement of sickness and any required supplemental doctor's statement shall be executed by any of the following individuals:
(1) A licensed medical doctor;
(2) A licensed dentist if the infirmity relates to the teeth or gums;
(3) A licensed podiatrist or chiropodist if the infirmity relates to the feet or toes;
(4) A licensed chiropractor;
(5) A clinical psychologist;
(6) A certified nurse mid-wife;
(7) The superintendent or other supervisory official of a hospital, clinic, or group health association, or similar organization, in which all examinations and treatment are conducted under the supervision of licensed medical doctors or under the supervision of licensed chiropractors, and in which medical records are maintained for each patient;
(8) A physician assistant-certified (PAC);
(9) An accredited Christian Science Practitioner;
(10) A substance-abuse professional as defined in 49 CFR part 40.3, if the infirmity involves alcohol or controlled substances-related disorders; or
(11) A nurse practitioner.
(b) Use of Board form or other form. The statement of sickness and supplemental doctor's statement referred to in paragraph (a) of this section shall be completed on the forms prescribed by the Board, except that other standardized medical forms may be substituted if they provide the same information as that called for by the Board's forms.