Introduction

The electronic health record ( EHR) is evolving from its fragmented paper based origins into a federated life-time medical record. As an enabler for improved patient care, the EHR promises the right information to the right people at the right time. This promise has been hard to realise. Clinical information is complex, diverse and volumous. The EHR system of the future is likely to be a federated collection of information from a variety of electronic medical records that together paint a longitudinal and holistic picture of a patient. Care delivery service oriented electronic medical records have and continue to be difficult to implement. A shared electronic health record (SEHR) will be even more demanding. Key to the shared EHR of the future will be architecture and standards to make the exchange of EHR extracts between EHR systems possible while preserving the medico-legal integrity of the patients record.

Current EHR standards efforts

Internationally, a number of groups are working to overcome the challenges of the shared EHR. Such groups include:

* HL7 - an international standards development organisation responsible for the HL7 V3 standard including a foundation reference information model (HL7 V3 RIM) as well as the clinical document architecture and templates.

* openEHR OpenEHR - a not for profit company responsible for the openEHR specifications. These specifications include the openEHR reference model and openEHR archetypes.

* CEN - the european committee for standardisation. The European health informatics committee (otherwise known as CEN/TC 251).

CEN 13606 EHR communication standard

CEN/TC 251 is defining and revising a five part EHR communication standard.

* Part 1 - Reference model (a scalable model for representing health information)

* Part 2 - Archetype interchange specification (an archetype model is used to represent archetypes when communicated between archetype repositories within EHRs). Archetypes define (constrain) legal combinations of the reference model (described in part 1)

* Part 3 - Reference archetypes and term lists

* Part 4 - Security (a methodology for specifying the privileges necessary to access the EHR data)

* Part 5 - Exchange models (still under development but will describe the messaging model to enable the exchange of EHR data)

The efforts of CEN, HL7, openEHR and others represent parallel efforts to define shared EHR standards. Harmonisation of these different approaches is gradually occurring and will help reduce the complexity of shared EHR implementations.

CEN 13606-1 Reference model

This article will overview the CEN 13606 reference model that underpins the exchange of EHR information. The CEN 13606 reference model is an information model that contains a set of classes and attributes. The CEN 13606 reference model is represented as a set of unified Modeling Language (UML) diagrams. The CEN 13606 reference model is a hierarchical model reflecting the hierarchical nature of real heath records. The CEN 13606 reference model is composed of a number of classes which build on each other to provide the representation of an EHR extract. These classes include:

* EHR Extract class:- identifies who the extract is about and what system the extract has been extracted from. EHR data is (optionally) comprised of directory of folders. The EHR data is made up of compositions (records authored together and committed to the EHR), demographics and access control policies

* Recorded component:- this is a super class of other classes. These record component classes build from a simple element to more an more complex structures These classes include:

* Element - a single value

* Item - a single element, a list of elements, a cluster or a list of clusters. Item therefore allows the representation of a wide range of data structures.

* Entry - items recorded for a single recording in the EHR (e.g. a single observation)

* Section - entries grouped together

* Composition - set of record components authored during a users clinical sessions and stored in the EHR (e.g. a progress note)

* Folders - allows grouping of the record. Folders can include other folders, compositions or used to organise (selected subset) of the EHR extract.

* Other classes such as audit, record linkages, access policy and message

Using such a hierarchy an EHR extract can be built starting with elements and then successively grouping into items, entries, sections, compositions and folders.

Summary

In summary the CEN 13606-1 reference model defines the information model for representing an EHR extract. It is composed of a set of hierarchical classes required to support communications between systems that request or provide EHR data.

About the Author

Peter Gillogley is the Director of Gillogley Services. For more information on EHR standards and EHR services please visit the Gillogley Services web site at http://www.gillogley.com

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