(a) The head of each agency must determine categories of physician positions for which there is a significant recruitment and retention problem, and physicians' comparability allowances may be paid only to physicians serving in positions in such categories.

(b) In determining categories of physician positions, the head of each agency must, as a minimum, establish as separate categories the following types of positions:

(1) Positions primarily involving the practice of medicine or direct service to patients, involving the performance of diagnostic, preventive, or therapeutic services to patients in hospitals, clinics, public health programs, diagnostic centers, and similar settings, but not including positions described in paragraph (b)(3) of this section;

(2) Positions primarily involving the conduct of medical research and experimental work, including the conduct of medical work pertaining to food, drugs, cosmetics, and devices (or the review or evaluation of such medical research and experimental work), or the identification of causes or sources of disease or disease outbreaks;

(3) Positions primarily involving the evaluation of physical fitness, or the provision of initial treatment of on-the-job illness or injury, or the performance of preemployment examinations, preventive health screenings, or fitness-for-duty examinations; and

(4) Positions not described by paragraph (b) (1), (2), or (3) of this section, including positions involving disability evaluation and rating, the performance of medicolegal autopsies, training activities, or the administration of medical and health programs, including the administration of patient care or medical research and experimental programs.

(c) The agency head may establish as separate categories any additional subdivisions of these four categories of positions, based on any factors the agency head determines relevant. These may include such factors as the location, grade or level, and medical specialization of the positions, and the level of qualifications sought by the agency for physicians in the category.