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Building Blocks for Decision Support in HL7

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)

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Building Blocks for Decision Support in HL7

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  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

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