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Building Blocks for Decision Support in HL7
Samson W. TuStanford Medical InformaticsStanford University School of
Medicine Stanford, CA
Outline
HL7 Clinical Decision Support TC Representation of DS knowledge
Arden Syntax Clinical practice guideline (CPG)
Building blocks of CDS based on CPG
Messages
HL7 Clinical Decision Support TC: History and Structure
Arden Syntax first met as part of HL7 in 1997
Version 2.0 formally transferred to and adopted by HL7 and ANSI in August, 1999
CDS TC synonymous with Arden Syntax up to 2000 St Louis meeting
Current Structure Arden Syntax SIG Clinical Guideline SIG Clinical Trial SIG
CDS TC Membership Vendors
Micromedex, Siemens, SMS, Eclipsys, Epic...
Healthcare Providers LDS Hospital, Intermountain Health
Care... Academic
Newcastle, Harvard, Columbia, Stanford, Yale, UT-Houston, ...
Shared Interests of CDS TC Single-patient-focused healthcare Common interest in decision-support
knowledge representation Arden Syntax Clinical practice guidelines as marked-up
documents and as computable knowledge base
Development of standards based on HL7 methodology and collaboration
Outline
HL7 Clinical Decision Support TC Representation of DS knowledge
Arden Syntax Clinical practice guidelines
Building Blocks of CPG Messages
Arden Syntax and Medical Logic Module
MLM designed to share medical knowledge required for making a single decision
Mature standard Decade-long evolution Supported by multiple vendors Continuously refined
Current projects Fuzzy-logic extensions of Arden Syntax XML format - multiple levels Object-oriented data model and expression
language
Challenges for Arden Syntax Simple data model
Variables with time-stamped values Curly braces problem
No structured way to access institution-specific
MLM-specific mappings Integration with HL7 version 3 RIM
and methodology
Representation of Clinical Practice Guidelines for CDS Current focus of decision-support
research Numerous formalisms for representing
guidelines PROforma, PRODIGY, PRESTIGE,
PacMan/Guide, EON, Asbru, GLIF, … CDS TC takes a component view
Has not endorsed a particular formalism Work on building blocks
Building Blocks of DS Using Clinical Practice Guidelines
GoalsGuidelineProcesses
achieve/maintain
Decisions
Actions
organize
ExpressionLanguage
PatientData Model
(VMR)
Medical Concept Model
Standard MedicalTerminology
uses
depends onuse
use/build on
EMR/Host Systems
Guideline Model
…
CPG Component: Goals Difficult to extract from existing guidelines
Often not explicitly stated Need to be operationalized
Research issues Representation Multiple uses
For comparison with clinicians’ goals As reason for making choice of intervention As constraints
Patient-specific goals
CPG Component: Decision Model Making choice among alternatives Many alternative models
Conditional rule Pros-and-cons argumentation
With or without weighting Decision-theoretic approach
Allows patient preference
CPG Component: Action Model Specification of acts to be performed Issues to resolve
System vs. medical actions e.g. send a message vs. order a test
Temporal specification e.g. return appointment in 3 months
High-level action and refinement e.g. prescribe an ACE inhibitor
Use of standard medical terminology e.g. order a specific laboratory test
Opportunity to leverage HL7 products (e.g. Act class in RIM and work of O/O TC)
CPG Component: Process Model Organizes decisions and actions
over time Sequencing, repetition and
concurrency of actions and decisions Hierarchical decomposition of
processes Different kinds of processes Represented as diagrammatical
flowchart
Example of Guideline Management Process
Concurrent actions
Alternative choices
Actionstep
If-then-elsedecision
Patientscenario
Subguideline
Toward a Common Process Model
Requirements Integration of decision making and activity
sequencing Expressiveness
Allows sequencing, repetition, and concurrency (branching and synchronization)
Visual Clarity Well-understood and formal semantics
Problems with current guideline models PRODIGY3: Augmented Transition Network PROFORMA: Constraint Network EON/GLIF: Operational semantics
Workflow as Basis for Common Process Model
Workflow management Controlling, monitoring, optimizing and
supporting business processes Explicit representation of the business logic
that allows computer support Workflow Process Definition Language
Version 1.1 (October 29, 1999) Defined Workflow Management Coalition
Good properties Formal semantics (mapping to Petri net) Concordance with the RIM
Integration of Decisions and Workflow Activities
Add clinical states and decision steps as nodes in flowcharts
Separate decision-making and workflow functionalities
CPG Component: Expression Language Core of decision-support knowledge
If systolic BP > 140 and presence of DM and ACE inhibitor is not contraindicated…
an episode of uncontrolled blood pressure that follows the initiation of lisinopril within two weeks…
Requirements A data model for patient information Reference to medical concepts and knowledge Expression of temporal relationships Use of abstraction
Old and New Expression Languages Arden Syntax as guideline expression
language Mapping of complex datatypes into Arden Loss of expressiveness
New object-oriented expression language being developed Use of HL7 datatypes Use VMR Built-in classes and methods and
declaration of new ones
CPG Component: Medical Concept Model Defines:
medical concepts used in guidelines relationships among concepts abstractions
Classifications (diabetes mellitus) Deriving categorical values from
numerical data (abnormally elevated serum cholesterol)
Defining concepts in terms of others
Why Not Use Standard Vocabulary Directly?
Need strict classification hierarchy
Allows definition of guideline-specific concepts and axis of classificationDM not taking ARB:
Presence of DM and absence of prescription for angiotensin II receptor blockers
Organizes mappings to host-system data dictionary
Diabetes
DM type 1 DM nottaking ARB
Relationship to Standard Vocabulary Possible relationships
Vocabulary service as source of medical concept model
Host system vocabulary as target of terminology mapping
Challenges Leverage work of done elsewhere Distinguish vocabulary service from
functions of knowledge base
CPG Component: Patient Data Model Must be standardized
support expression language support mapping to multiple EMRs
VMR talk at this meeting
Outline
HL7 Clinical Decision Support TC Representation of DS knowledge
Arden Syntax Clinical practice guidelines
Building Blocks of CPG Messages
Messages Between DSS and External Agents
Arden Syntax and MLM Input: triggering event and clinical data Output: alerts and reminders
CDSS for guideline-based care Rich collection of messages needed
Recommendations for interventions, decision to select a choice, requests for data, …
Much remain to be done
Summary Arden Syntax and MLM a mature standard
with industry support Current work centered around
standardization of format and infrastructure needed for guideline-based case
Standardization of clinical guidelines still in infancy Current work looking at components of
guidelines Requires collaboration with many other
committees