Transcript Document
Building Blocks for Decision
Support in HL7
Samson W. Tu
Stanford Medical Informatics
Stanford 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
Healthcare Providers
Micromedex, Siemens, SMS, Eclipsys,
Epic...
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
Curly braces problem
Variables with time-stamped values
No structured way to access institutionspecific
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
Guideline
Goals
Processes
achieve/maintain
organize
Actions
Guideline Model
EMR/Host Systems
Decisions
uses
…
Expression
Language
depends on
use
Medical Concept
Model
Patient
use/build on
Data Model
Standard Medical
(VMR)
Terminology
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
Temporal specification
e.g. prescribe an ACE inhibitor
Use of standard medical terminology
e.g. return appointment in 3 months
High-level action and refinement
e.g. send a message vs. order a test
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
Action
step
If-then-else
decision
Alternative
choices
Patient
scenario
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
Workflow Process Definition Language
Controlling, monitoring, optimizing and supporting
business processes
Explicit representation of the business logic that
allows computer support
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 decisionmaking 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 classification
DM 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 not
taking 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