The Patient Demographics Query HL7 v3 (PDQV3) Integration Profile is part if the IHE IT Infrastructure technical framework.

This profile has the same functionality as the Patient Demographics Query (PDQ) profile. The differences in the new PDQV3 profile are in the format of the messages, and in the use of SOAP-based web services. These changes make this new profile well suited for use within an  existing IT infrastructure for cross-enterprise data access and exchange. This new profile provides ways for multiple organizations, or multiple distributed applications to query a central patient information server for a list of patients, based on user-defined search criteria, and retrieve a patient's demographic information directly into an application.

Source: IHE IT Infrastructure Technical Framework Supplement 2008-2009: PIXV3 and PDQV3