Guide on Use of SNOMED Clinical Terms (SNOMED CT) Concepts in the HL7 Version 3 Communication

Guide on use of SNOMED Clinical Terms concepts in HL7 Version 3 communication standards

Draft outline structure proposed by David Markwell 2005-03-01

1. Introduction 1

2. General considerations 2

Representation of SNOMED CT in coded attributes 3

3. Semantic Objectives 4

4. Vocabulary Domain constraints expressed in SNOMED CT 4

5. Class-by-Class consideration of applicability of SNOMED CT as a possible or appropriate code system for specific attributes 4

6. HL& Act mood,status and SNOMED CT context 5

7. ActRelationships and SNOMED CT post-coordination 6

8. Participation and SNOMED CT Subject Relationship Context 6

9. Context Conduction in relations to context expressed through Participation, ActRelationships or elements of the SNOMED CT Context Model. 7

1. Introduction

Purpose of the guide

The purpose of this guide is to ensure that HL7 Version 3 standards achieve their stated goal of semantic interoperability when used to communicate clinical information that is represented using concepts from SNOMED Clinical Terms (SNOMED CT).

Background

The guide has been developed by the HL7 TermInfo Project (a project of the Vocabulary Technical Committee). The guide is the result of a consensus process involving a wide range of interested parties.

· The HL7 Project of Clinical Statement Project and the various Technical Committees contributing to that project.

· The SNOMED International Concept Model Working Group.

· Vendors and providers actively implementing HL7 Version 3 with SNOMED CT.

· The UK NHS National Programme for Information Technology

The guide takes account of:

· The SNOMED CT Concept Model including those elements concerned with the representation of context.

· The structure and semantics of the HL7 Reference Information Model (RIM).

Overview

The guide identifies gaps between these models and areas in which they overlap. It provides coherent guidance on how these gaps can be bridged and the overlaps managed to meet the common goal of semantic interoperability.

The guide identifies options for use of SNOMED CT concepts, in both pre and post-coordinated forms in various attributes of HL7 RIM classes. The primary focus is on the RIM class clones used in the HL7 Clinical Statement pattern. However, the general principles of the advice are also applicable to many RIM class clones used in other constrained information models as that form part of HL7 specifications and standards.

In some situations, the features of HL7 Version 3 and SNOMED CT dictate a single way to utilize these two models together. Where this is true the guide contains a single recommended approach and in some cases this may be regarded as normative, based on referenced pre-existing standards.

In other situations, there are several possible ways to combine HL7 and SNOMED CT to resolve a gap or overlap. In these cases, the advantages and disadvantages of each option are evaluated. The guide explicity recomments against approaches only where there is a consensus that it has a disproportionate balance of disadvantages and is unlikely to deliver semantic interoperability. As a result the guide contains advice on several alternative resolutions for some of the issues raised. Where more than one approach appears to be viable, advice is included on transformation between alternative representations of similar information.

2. General considerations

These sections should be brief. Mostly referencing source material from HL7 and SNOMED rather than repeating this material.

2.1. Information Model - HL7 Reference Information Model

2.1.1. Structural attributes

2.1.2. Coded data types

2.1.3. Vocabulary domain constraints

2.1.4. Clinical statement constraints

2.1.5. Templates

2.2. Terminology Model - SNOMED CT Concept Model

2.2.1. Concepts, description and relationships

2.2.2. Description logic, subsumption and equivalence

2.2.3. Pre-coordination and post-coordinated refinement

2.2.4. SNOMED CT Context Model

Representation of SNOMED CT in coded attributes

Illustrations of the use of SNOMED CT in the Concet Descriptor data type.

Rationale for adoption of extended CD data type including <group> element.

3. Semantic Objectives

3.1. Communication of information in ways that supports consistent and efficient retrieval

3.2. Transformability between alternative forms without semantic loss where multiple approaches exist

4. Vocabulary Domain constraints expressed in SNOMED CT

4.1. SNOMED CT Subsumption constraints

4.2. SNOMED CT subset/refset constraints

4.3. Impact of SNOMED CT post-coordination on value set constraints

4.4. Managing alternative views of Vocabulary Domain boundaries

5. Class-by-Class consideration of applicability of SNOMED CT as a possible or appropriate code system for specific attributes

5.1. Act

5.1.1. General

1.1.1.1 code

1.1.1.2 reasonCode

5.1.2. Observation

1.1.1.3 code

1.1.1.4 value

1.1.1.5 interpretationCode

1.1.1.6 methodCode

1.1.1.7 targetSiteCode

5.1.3. Procedure

1.1.1.8 code

1.1.1.9 methodCode

1.1.1.10 approachSiteCode

1.1.1.11 targetSiteCode

5.1.4. Substance Administration

1.1.1.12 code

1.1.1.13 routeCode

1.1.1.14 approachSiteCode

1.1.1.15 administrationUnitCode

5.1.5. Supply

1.1.1.16 code

5.1.6. PatientEncounter

1.1.1.17 code

1.1.1.18 admissionReferralSourceCode

1.1.1.19 dischargeDispositionCode

5.2. Role

5.2.1. General

1.1.1.20 code

5.3. Entity

5.3.1. code

6. HL& Act mood,status and SNOMED CT context

6.1. Observations and SCT Finding Context

6.1.1. SCT findings

6.1.2. SCT observables + value

6.1.3. SCT procedure + value

6.2. HL7 Procedures and SCT Procedure Context

6.2.1. SCT procedures (no value)

6.2.2. SCT observables (no value)

7. ActRelationships and SNOMED CT post-coordination

7.1. Use of related Acts as qualifiers

7.2. Use of ActRelationships for containment. Related rules on naming containers (e.g. using SNOMED CT or other terminologies and impact on semantics and context of contained Acts.

7.3. Use of related Acts to represent causal and other specific relationships as compared to post-coordination using SNOMED CT attributes

7.4. Cases where information model prevails

7.4.1. ActRelationships for business process driven relationships (fulfilment etc)

7.4.2. Update semantic uses of ActRelationships such are revision and replacement

7.5. Judgement based assertions of relationships

7.5.1. Use and limitations of simple ActRelationships

7.5.2. Condition nodes, threads and problem orientation. Naming of threads and problems.

7.5.3. "Statement Relationships" and coding of the nature and context of the relationship

8. Participation and SNOMED CT Subject Relationship Context

8.1. Family history

8.2. Donors

8.3. Contacts

8.4. Others

9. Context Conduction in relations to context expressed through Participation, ActRelationships or elements of the SNOMED CT Context Model.