US HITSP: T67: Document-based Referral Request - DRR. The Clinical Referral Request Transport Transaction will be used to transport the provider to provider (clinical) referral request interaction. It is based on the Integrating the Healthcare Enterprise (IHE) Document-based Referral Request (DRR) profile which is used to bundle a referral request document with other relevant clinical documents of interest and optionally to send a trigger message to the receiving provider system. View the most current version as HTML here.