An advance directive may authorize an agent to approve participation by the declarant in any health care study approved by an institutional review board pursuant to applicable federal regulations, or by a research review committee pursuant to Chapter 5.1 (§ 32.1-162.16 et seq.) of Title 32.1 that offers the prospect of direct therapeutic benefit to the declarant. An advance directive may also authorize an agent to approve participation by the declarant in any health care study approved by an institutional review board pursuant to applicable federal regulations, or by a research review committee pursuant to Chapter 5.1 (§ 32.1-162.16 et seq.) of Title 32.1 that aims to increase scientific understanding of any condition that the declarant may have or otherwise to promote human well-being, even though it offers no prospect of direct benefit to the patient.