Health Information Exchange (HIE) focuses on the mobilization of healthcare information electronically across organizations within a region or community. HIE provides the capability to electronically move clinical information between disparate health... Series. Part 4 of 6.
In the first three posts in this series on Health Information Exchange I discussed thedifferent  motivators  that are driving health organizations to connect to HIEs, the three different architecture types  of HIEs, and the fact that future financial sustainability is a real concern  for public exchanges. In this post, I’ll describe some common HIE terms that you’re likely to encounter when researching or discussing HIEs.
One thing to keep in mind when reading about HIEs and how they operate, at least from my experience, is that the terminology is not consistently used by health IT professionals, which only complicates the learning process. For example, you’ll notice below that the definitions for Document Registry and Record Locator Service have very similar definitions, and you’ll often find they are used interchangeably in discussions and in publication. Hopefully these terms provide a foundation to help you better understand the complicated, and always changing, world of health information exchange.
Clinical Data Repository (Clinical Document Repository (CDR) enables hospitals to build a life-long health record environment using stored health records for the purpose of better treatment, clinical research and health statistics for policy making. Synonyms: Clinical Documen...): The database in which patient data is stored. Regardless on the HIE architecture type, each member organization maintains their own CDR. Centralized HIEs have a CDR that houses a redacted version of the complete patient medical record, which is easily accessible by all member organizations.
Communication Backbone: The method by which data is transmitted within an HIE. Communication methods include secured email, secured FTP, secured Web services, and Transmission Control Protocol/Internet Protocol (TCP/IP) is a low-level communications protocol used to connect hosts on the Internet or a network. TCP/IP connections are established between clients and servers via sockets. TCP/IP is stream-oriented ... via VPN connection. HIE components that need to be regularly updated may include: Master Person Index, Record Locator Service, CDR, and Portals. Part 5 of this series will provide more information on communication methods.
Document Registry: A document registry is best described as the “patient index” of each patient who has health information that is accessible by the HIE, and contains information where that information is stored. The health standards organization Integrating the Healthcare Enterprise (IHE) has worked at defining document registries, which are available in evolving Web-services technology. You can read the current Document Registry specifications on the IHE wiki page under the heading “Interpreting Web Services Specifications for XDS.b and XCA .”
Master Person Index (MPI): Stores, and cross references, the unique ID is a coded value data type. The value of such a field follows the formatting rules for a ST field except that it is drawn from a table of legal values. Examples of ID fields include religion and sex. for every patient in the HIE.
Portal: Provides independent, personal access to the HIE for the treating physician or for the patient to view and access information, which can include hospital paperwork, appointment information and personal health information.
HIE Participant Identity Management: HIE member providers and networks are verified by node level identity management, as defined by IHE Audit Trail and Node Authentication standards . Node level identity management establishes security measures that, together with the HIE’s security policy and procedures, provide patient information confidentiality, data integrity and user accountability.
Record Locator Service (RLS): Keeps track of all records for a single patient. The location of the RLS varies depending on the HIE architecture type. Centralized HIEs have a common CDR housing basic patient demographic information. Typically, a centralized HIE member issues a patient query to the RLS, which locates the correct patient’s data and sends the location back to the requesting organization – all within the centralized HIE.
In Federated and Hybrid HIEs, all patient data is maintained by and “lives” in the member’s CDR (not in a centralized location). When the RLS receives a patient query, it must relay all participant organizations, rank the responses, and then return the information to the original requester – a much more complicated process than in a centralized model.
Check back next week for the fifth part of the series. I’ll try to further explain the different communications methods that can be used to send and receive data in HIEs.
Topics in this HIE series include:
Part 1: Health Information Exchange: What’s the Motivation? 
Part 2: Architecture Types 
Part 3: Despite Momentum, HIE Sustainability a Concern 
Part 4: The Building Blocks of HIEs: A Glossary of Terms 
Part 5: HIE Communication Methods 
Part 6: HIE Physician and Patient Portals 
Round Table on HIE Connectivity: Real Experiences with Health Information Exchanges 
EHR/HIE Interoperability Workgroup Releases Technical Specifications 
Meaningful Use, EHR Certification, & Healthcare Integration