Building Blocks for Decision Support in HL7

1. Building Blocks for Decision Support in HL7 Samson W. Tu Stanford Medical Informatics Stanford University School of Medicine Stanford, CA

2. Outline • HL7 Clinical Decision Support TC • Representation of DS knowledge • Arden Syntax • Clinical practice guideline (CPG) • Building blocks of CDS based on CPG • Messages

3. 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

4. CDS TC Membership • Vendors • Micromedex, Siemens, SMS, Eclipsys, Epic... • Healthcare Providers • LDS Hospital, Intermountain Health Care... • Academic • Newcastle, Harvard, Columbia, Stanford, Yale, UT-Houston, ...

5. 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

6. Outline • HL7 Clinical Decision Support TC • Representation of DS knowledge • Arden Syntax • Clinical practice guidelines • Building Blocks of CPG • Messages

7. 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

8. 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

9. 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

10. Building Blocks of DS Using Clinical Practice Guidelines Guideline Processes Goals Decisions organize achieve/maintain uses … Actions Expression Language use depends on Guideline Model Medical Concept Model Patient Data Model (VMR) use/build on Standard Medical Terminology EMR/Host Systems

11. 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

12. 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

13. 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)

14. 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

15. Action step Concurrent actions If-then-else decision Alternative choices Subguideline Patient scenario Example of Guideline Management Process

16. 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

17. 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

18. Integration of Decisions and Workflow Activities • Add clinical states and decision steps as nodes in flowcharts • Separate decision-making and workflow functionalities

19. 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

20. 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

21. 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

22. Diabetes DM type 1 DM not taking ARB 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 forangiotensin II receptor blockers • Organizes mappings to host-system data dictionary

23. 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

24. CPG Component: Patient Data Model • Must be standardized • support expression language • support mapping to multiple EMRs • VMR talk at this meeting

25. Outline • HL7 Clinical Decision Support TC • Representation of DS knowledge • Arden Syntax • Clinical practice guidelines • Building Blocks of CPG • Messages

26. 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

27. 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