Archetypes in HL7 v2

Andrew McIntyreMedical-Objects

HL7 InternationalMay 2009

Overview

HL7 v2 in widespread use in Australia Many legacy applications Administrative models well covered Limited support for Clinical Models

Need for Structured Clinical data SNOMED-CT support Patient history/Family History transfer Decision Support Registries

Archetypes allow detailed Clinical Models No changes required to standard Backward compatible

Long-term goals

Support of Complex Clinical Models No limit on complexity

Allow reuse of models Represent model in V2/V3/CDA/CCD formats

Smooth migration of legacy applications Complexity hidden from legacy applications

Common clinical models in use Allows data transfer across systems Allows data transfer across encodings

Allow rich SNOMED-CT use Support post-coordination

The Present Australian Situation

Clinical Models basic Blob of text in single OBX Blob of RTF (un-escaped) in single OBX Little or No semantic interoperability Opaque documents eg. PDF No atomic data, minimal terminology

Pathology Models improving Atomic data Terminology (LOINC) in private labs Hamstrung by unreliable imports of HL7 Many packages lack CE (Coded Entry) support

Development up to present

2006: Archetypes in V2 implementation Part of Medical-Objects ITOL project “Lymphoma wizard” Archetypes for Registry notification Archetypes for GLIF/GELLO data structures Total HL7 solution

Experience used to inform standards work Proven round trip semantic interoperability CEN Archetypes used Used for AS4700.2 Lab system with GELLO

Messages are being delivered to existing PMS systems now

Archetypes

Built on a domain model CEN 13606 – European Standard OpenEHR

Domain model is mappable Existing HL7 V2 data models Medication/Allergies already exist

Archetype content is mapped to OBX segments or messages Existing HL7 semantics are preserved Existing applications are mostly unaware Minimal overhead

Archetypes

Describe semantic relationships Between atomic data items Between archetypes Between/within terminologies

Constrain data Occurrences Cardinality Terminology Datatypes/Constraints

Provide metadata that is lacking Potential overlap with SNOMED-CT/V3 models Minimal overlap with V2 Exception is Medications/Allergies

Archetypes

Allow organisations to define data structures Discharge summaries Registry notification Referral requirements/prerequisites Notifications EHR notes transfer

Ideally standard Archetypes used Allow easy interoperability Some metadata better than none however Decision support needs flexibility to define its

own custom data structures

Archetype Options

CEN Archetype Generic structure Standards based Developed in conjunction with OpenEHR

OpenEHR Similar to CEN Have diverged Extended semantics that are OpenEHR specific Not a formal standard

CEN Philosophy

The challenge for EHR interoperability is to devise a generalised approach to representing every

conceivable kind of health record data structure in a consistent way. This needs to cater for records

arising from any profession, speciality or service, whilst recognising that the clinical data sets, value

sets, templates etc. required by different health care domains will be diverse, complex and will

change frequently as clinical practice and medical knowledge advance. This requirement is part of the widely acknowledged health informatics challenge

of semantic interoperability.

Example Archetypes

Archetype Data Model

An Identifier for the Archetype A tree of Atomic data elements

Elements map to single OBX OBX - 4 Observation sub ID used

Organised by Non Terminal Nodes Nodes usually descriptive Data does not change Not required for semantics as can be inferred Useful for human readers “Headers” Represented by display OBX segment

Data model is not the same tree as metadata Occurences > 1 in archetype requires extra

nodes

The HL7 V2 Version

• Archetype Nodes have – Cardinality– Occurrences

• The data structure is similar to an xml representation– Dotted SubID used to build the tree

OBX Tree Structure

• Only nodes that are valued need inclusion• Missing nodes inferred by Archetype• Requires receiver to have access to

archetype for Semantic interoperability

Walking the path

OBX|6|NM|163031004^diastolic^SNOMED-CT^at0005^^openEHR-EHR-OBSERVATION.blood_pressure.v1|1.1.1.1.1.1.1.1.2|100|mm[Hg]^^ISO+|||||F

Overview of encoding

Three OBX types:

• Header RP Segment– OBX|1|RP|ENTRY^^EN 13606|1|openEHR-EHR-

OBSERVATION.blood_pressure.v1^Blood pressure measurement&99A-A892E160ECDB6613&L^TX^Octet-stream||||||F

• Non Terminal OBX– OBX|6|CE|15431-0^^LN^CLUSTER^^EN 13606|1.1.12|

103764000^Non reportable items^SNOMED-CT^at0047^Non reportable items^CEN-FULL-BLOOD-COUNT.v1||||||F

• Terminal OBX – “Data”– OBX|2|NM|14749-6^Glucose^LN^22569008^^SNOMED-CT|

1.1.6|7.8|mmol/L^^ISO+|<7.8|+|||F

Potential Alternatives

CDA Solves problem of inadequate HL7 parsers

This is small piece of puzzle however Does not solve all semantic issues Minimal existing CDA support in Australia Requires overnight upgrade of all pms systems

CCR/CCD ASTM standard +/- CDA format ?Useful for GP interoperability project Could be archetyped and carried in V2

Handbooks Provide detailed Human readable specs

Has not worked to date

Conclusions

Archetypes allow data models to be defined Usable in HL7 V2 and CDA Archetypes in V2 would allow migration

Requires solid HL7 parsers Prerequisite for any semantic interoperability Investment required in low level technology

Standards Compliance Would improve quality of existing messages Allows possibility of taking next step

Common archetypes ideal Useful without this however