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