HIE
Health Information Exchange (HIE)
The totality of a patients’ medical history often exists in disparate silos (offices, hospitals, clinics, etc.) making it difficult for clinicians to obtain complete data when caring for a patient. This is especially true when the patient receives care in separate locations from various providers. This has been recognized as a major source of inefficiency and a barrier to delivery of quality medical care[1]. To address this problem, health information exchanges (HIE) have been developing based on several standards and technologies. The process of health information exchange has been described as the data following the patient. It is a data-sharing model where the longitudinal health information for a particular patient can be accessed or referenced from an electronic source. This data can then be shared securely with an entity that has access to the data.
Driving this effort is an initiative by a collaboration of health care professionals and industry to improve the way computer systems in healthcare share information. This non profit collaboration is known as "Integrating the Healthcare Enterprise (IHE)[2] Through the development and publication of “integration profiles”, IHE has defined the standard processes and technologies needed to support an HIE framework[3]. Using common web technologies the data in an HIE is typically transmitted electronically in standard formats for the purpose of storage and retrieval.
Contents |
The Document
Extensible Markup Language (XML) is a standard markup language used in web technology and other computing platforms. XML is the language used to encode patient data that is transmitted within the framework of a health information exchange. The encoded information is referred as a “document”. The document includes text for human readability as well several vocabulary standards such as SNOMED and LOINC for machine readable, structured data. In this way the document can be consumed by an electronic health record or simply rendered by a web browser that is XML capable.
Two standards exist for the structural specification of the XML document. The first is a lean version of critical patient data called a continuity of care record (CCR). This is an American Society for Testing and Materials (ASTM) standard and its purpose was to encode a small set of common patient data such as demographics, medications, allergies and problems[4]. The second standard is a derivation of HL7’s common document architecture (CDA) format called the continuity of care document (CCD). This standard is based on CCR structure but adds more complexiy and has been designed to carry more data elements than the CCR. Although many have looked at these as competing standards, it is more accurate to say they are complementary[5]. The XML document is typically produced by an electronic health record (EMR) from a physician’s office, hospital or a personal health record. The CCD or CCR are the primary document structures in an HIE.
The Infrastructure
Once the document is generated it needs to be transmitted, stored, and then made available for an authorized user to "consume" the document. HIEs use web technologies such as TCP/IP for transport between destinations. There are many vendors in health care who provide HIE infrastructure. This infrastructure closely adheres to the standard profiles set by IHE. The infrastructure has multiple components but most notably includes:
- Cross enterprise document sharing (XDS) repository(s). These act as repositories to store the documents and can be centralized or federated.
- Cross enterprise document sharing registry(s) keep the metadata for each document. In this way a document can be located by querying the registry which links to the actual document in a repository.
- The cross community gateway (XCA) is the profile describing a connection between different HIE environments. Connecting HIEs though XCA technology allows a query to cross into other "connected" HIEs and retrieve patient information located in disparate repositories. In this way several HIEs can deliver federated information about a single patient.
- The patient identity cross-reference (PIX) or patient demographics query (PDQ) managers are program specifications that define the way a patient is identified in a registry. First and foremost in any HIE, proper patient identification is paramount to accuracy. The difficulty is that HIEs store documents belonging to one patient but generated from various entities such as hospitals or clinics. Each entity may not be working with a common patient identifier. Therefore a query needs to match the patient with the correct document using demographic information rather than a master patient index (MPI). The PIX or PDQ profiles, are 2 methods for cross-referencing the patient identity attributes.
Securing Information
No discussion of patient data exchange is complete without mentioning security. The audit trail and node authentication (ATNA) profile from IHE addresses many dimensions of privacy and security[6]. It requires data to by encrypted and also outlines a standard for authentication and authorization of data access. Data access and audit trails for reporting each transaction are also outlined in this profile.
References
- Institute of Medicine To Err Is Human: Building a Safer Health System. Washington, DC, National Academy Press. 2000.
- Integrating the Healthcare Enterprise. IHE.net Home. IHE International; 2010 [cited 2010 November 18]; Available from: IHE.org.
- RIngholm bv (2010) IHE: an implementation framework based on messaging standards, a whitepaper. Retrieved November 19, 2010, from http://www.ringholm.de/docs/00830_en.htm
- ASTM.org (2010) E2369 -05e1 Standard Specification for Continuity of Care Record (CCR. Retrieved November 19, 2010, from http://www.astm.org/Standards/E2369.htm
- David Kibbe. (2010) The Health Care Blog: Untangling the electronic health date exchange. Retrieved November 19, 2010, from http://www.thehealthcareblog.com/the_health_care_blog/2008/06/untangling-the.html
- Integrating the Healthcare Enterprise (2010) iti10_ihewkshp07_xca_witting.pdf. Retrieved November 19, 2010, from http://www.ihe.net/Participation/upload/iti10_ihewkshp07_xca_witting.pdf
Submitted by Neil Meehan
