(a) The privilege of confidentiality may be claimed by:
(1) the patient;
(2) a person listed in Section 611.004(a)(4) or (a)(5) who is acting on the patient's behalf; or
(3) the professional, but only on behalf of the patient.
(b) The authority of a professional to claim the privilege of confidentiality on behalf of the patient is presumed in the absence of evidence to the contrary.