Archetypes in HL7 2.x

Snomed-CT“Computable Medical Records”

Andrew McIntyreMedical-Objects

http://www.medical-objects.com.au/

NEHTA Snomed-CT Workshop

Terminology is for Computers

• Humans understand text pretty well

• Computers are pretty hopeless at it– Much better with codes– Can manage much more in memory– Are obsessive and tireless– A path to decision support– Snomed-CT is for computers

Focus Concept

Attributes = Post Co-Ordination• Attributes are defined by model

– Vary depending on type of statement– Qualify concepts

Context of Statements• Past History

• Family History

• Planned

• Possible etc

• Every statement needs context– Default context

• Known present• About patient• Current or specified

Context added to statements• Removes much ambiguity

Context Example• Procedure Context

• These are “Values”

Snomed –CT• Abstract logical Model under development

– Conflicts/overlaps with some HL7 V3 structures

• HL7 V2 has administrative models– Limited clinical model (Medication mainly)

• It is possible to represent Snomed-CT Abstract Logical Model in HL7 V2

• Requires tree structures within groups of OBX segments – Archetyped HL7 V2

Snomed Model• Nested Name=Value pairs

In HL7 V2.3.1• OBX segments are designed to carry

NAME=VALUE pairs with date

• Dotted Sub-ID for structure

• Relatively simple display rules –linear display is possible

Archetypes in V2• Very Compact representation• OBX Sub-ID used for structure• Only value nodes need to be included• Works with existing display logic• Requires CE support!• Full semantic transfer• SNOMED-CT Abstract model transmitted• Requires knowledge of archetype

Multiple Inheritance Model• Eg Cholecystectomy

Multiple Inheritance

Gello Statement

Requires Patient Model

Expressing Snomed-CT Model• Snomed Grammar

• Fully supported by GELLO

Gello Can Exploit This

Gello can validate

Need to ensure statements are valid wrt Model

GELLO equivalence

Snomed Constraints

Archetype base Constraintsrestricts user to correct terms

Constraint Specification

MO Terminology Server• Uses HL7 V2 or SOAP interface• Lookup support with constraints• Canonical form support• Can run locally or remotely (transparent)• SOA architecture• GELLO integration• Caches frequently used queries locally• Available now via Communications clients

Summary• Snomed-CT allows high level computability

• Must follow Snomed-CT Model

• Needs more structure– Archetypes in HL7 V2 can do this– Archetypes can constraint choices

• Gello, vEMR and Terminology Server allow computable medical Records

• Standards urgently needed for interoperability of records

Resources• GELLO and GLIF demo available• www.medical-objects.com.au