The confidential communications between licensed or certified allied health practitioners and their clients or patients are placed on the same legal basis as those between physician and patient, and, except as otherwise provided by law, no allied health practitioner shall be required to disclose such privileged communications. Confidential communications between a patient or client and any person working under the supervision of such practitioner that are customary and necessary for diagnosis and treatment are privileged to the same extent as though those communications were with the supervising licensed or certified allied health practitioner. This section shall not apply to investigations and hearings conducted by the governing boards or by any other agency regulating health professions in the state.