Section 4. No person shall maintain a clinical laboratory in the commonwealth apart from a hospital or clinic licensed under section fifty-one of chapter one hundred and eleven, unless he holds, and there is in effect, a license issued under section five except that the licensing requirement of this section shall not apply to: (a) a clinical laboratory maintained by not more than two licensed physicians exclusively in connection with the diagnosis and treatment of his own patients; (b) a clinical laboratory maintained by three or more licensed physicians exclusively in connection with the diagnosis and treatment of his own patients; provided, however, that (i) the physician or his assistant under the direct supervision of such physician performs all testing; and (ii) the clinical laboratory performs only laboratory tests which the commissioner, with the advice of the advisory committee on clinical laboratories, has determined to be exempt from licensure; or (c) in the case of a clinical laboratory maintained exclusively for research and teaching purposes and not providing reports for diagnosis and treatment of patients or for a public health purpose; or (d) any laboratory with respect to tests or other procedures made by it for any person engaged in the business of insurance if made for purposes of determining whether to write an insurance contract or determining eligibility or continued eligibility thereunder, or for the examination of its employees or officers; or (e) any laboratory maintained exclusively for a health promotion screening program, as defined in regulations of the department, which does not provide reports for diagnosis or treatment of patients and which meets standards for such program established by the department. No provision of this chapter other than section six shall apply to any agency of the commonwealth; nor shall any provision of this chapter relative to licensing apply to any hospital or clinic licensed under section fifty-one of chapter one hundred and eleven.