Assessing the use of archetypes in ED Information System Jon Patrick, Richard Ly Centre for Health informatics Research & Development Donna Truran, National Centre for Classification in Health

Outline Project Description openEHR Basic Principles Data Model Reference Model & Archetypes Model Archetypes Data Model Archetype Data Dictionary (ADD) Demographics Model (DM) Generic Data Structure (GDS) Composition Package Findings and Issues

Project Description Problem: Objective Emergency Department (ED) Information System lacks interoperability, intelligent querying, effective use of terminology. Medical environment is highly volatile. Objective Investigating openEHR Architecture by developing a data model Feasibility of using openEHR as a basis for an ED Information System

Introducing openEHR openEHR – open Electronic Health Record Goals: International organisation. Goals: Interoperable health systems Life Long health records

openEHR idea 2 level frame work: Why? Reference Model (RM): Information model Semantics of storing and processing in system Archetype Model (AM): Knowledge model Domain level structure and constraints placed on the RM Why? Separate knowledge (domain experts) and information (IT experts) models. Interoperability

Archetype Archetypes are fundamental to openEHR. Definition: “An archetype is a formal expression of a distinct, domain level concept, expressed in the form of constraints on data whose instances conform to some RM”

Methodology Archetype Data Dictionary Demographics Model Generic Data Model Reference Model Persistent Layer

Data Model

Archetype Data Dictionary (ADD) ADD is a repository of archetypes Contains the definition of archetypes. Enables software layer to correctly instantiate EHR data by ensuring these instances adhere to defined archetypes.

Archetype Data Dictionary

Archetype Data Dictionary 1. Archetype Name and Type 3. Constraints on attributes 2. Archetype elements

Demographics Model (DM) openEHR assumes distributed model Demographics model describes any party who has interaction with health care facility. In an ED Information System, demographics model will record patient administrative data. Similar to Patient Master Index (PMI) in EDIS

Demographics Model (DM)

Generic Data Model (GDM) A generic data structure flexible enough to model most, if not all logical structures in clinical records. Why? It is the basis for storing instances of archetyped information in a relational database. It must cater for: Instantaneous and interval measurements Historical and Time series events Structures: SINGLE, LIST, TREE, TABLE

Generic Data Model (GDM)

Generic Data Structure Logical Form Physical Form

Generic Data Structure 2. Generic Structure type 1. Data identifier 4. Attribute’s associated values 3. Data Attributes

Findings and Issues Performance – Retrieving, Storing, Querying Complexity Interoperability Advantages and Disadvantages of the architecture.

Performance Entity-Attribute-Value (E.A.V) modelling allows representation of generic data structures in a relational database. However, it has performance trade offs. Insertion, retrieval, validation and querying can be costly due to the amount of processing required to reconstruct information from generic tables.

Performance According to a performance study on E.A.V modelling by Yale University; “E.A.V modelling can be up to 3 to 5 times less efficient than its conventional counterpart (traditional modelling methods)” “… differences in query efficiency became greater as database size increased” Source: Ronald S. Chen et. al. (2000). ‘Exploring Performance Issues for a Clinical Database Organised Using an Entity Attribute Value Representation‘ Journal of the American Medical Information Association. Pp 475-478

E.g. SQL Querying What is a SQL statement to find: The NMDS information relating to an ED visit from patient with health record = 1?

1. Select all appropriate attributes ehr.EHR_ID, ehr.PATIENT_ID, ehr.EHR_DATE_TIME_STAMP, c.COMPOSITION_COMPOSER, ec.HEALTH_CARE_FACILITY, ec.EVENT_CONTEXT_START_TIME, ec.EVENT_CONTEXT_END_TIME, ds.DATA_STRUCTURE_TYPE, ds.DATA_STRUCTURE_NAME, its.ITEM_STRUCTURE_NAME, i.ITEM_NAME, ev.ELEMENT_VALUE, ev.ELEMENT_UNIT FROM EHR AS ehr, COMPOSITION AS c, EVENT_CONTEXT AS ec, DATA_STRUCTURE AS ds, ITEM_STRUCTURE AS its, ITEM AS i, ELEMENT_VALUE AS ev WHERE ehr.EHR_ID = c.EHR_ID And c.COMPOSITION_ID = ec.EVENT_CONTEXT_ID And ec.EVENT_CONTEXT_ID = ds.STRUCTURE_ID And ds.DATA_STRUCTURE_TYPE= 'EVENT_CONTEXT' And ds.DATA_STRUCTURE_ID = its.ITEM_STRUCTURE_ID And its.ITEM_STRUCTURE_ID = i.ITEM_STRUCTURE_ID And i.ITEM_ID = ev.ELEMENT_VALUE_ID And ehr.EHR_ID = 1; 2. Join generic tables 3. Filter joined tables for correct rows

Advantages of openEHR Interoperability Generic data structures Use of shared repository of archetypes allows information exchange between systems. Generic data structures Adaptable to other health systems. Information model does not have to be altered if domain knowledge changes. Life long electronic health records

Disadvantages of openEHR Performance issues Significant overhead in processing Recall E.A.V modelling 3 to 5 times less efficient than conventional modelling. Models are very generic Not intuitive conceptually. Complex attribute querying is less efficient and technically more difficult. Must get everyone to agree on a set of archetypes Archetype governance

Python Implementation (Brendan Cheng) Model Complexity 3 models Reference Model, 5 packages, 90 classes Archetype Model, 10 packages, 40 classes Service Model 30% of first 2 models implemented in 3,000 lines Content is strongly coupled and complex Prescription archetype requires 30 classes

Implementation contd. The interconnection means all classes must be implemented before testing can begin. Sometimes there is no clear or detailed explanation (600 pages of specs spread across 10 files) E.g. logical_paths (a_lang:String): Set<String> Def. Set of language-dependant paths extracted from archetype. Paths obey the same syntax as physical_paths, but with node_ids replaced by their meanings from the ontology

Implementation contd. More variables, arguments & functions in the Eiffel implementation than in the Specification Answers from the Open EHR team are not always informative and indicate the documentation is not always in sync with specification: “It has already been implemented in Java and C# actually, so we should be able to find out the approach used by those two groups”

Future Work Complete implementation of generic OpenEHR in python Develop a version for ED

Questions ?