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 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 Goals Guideline Processes achieve/maintain Decisions Actions organize Expression Language Patient Data Model (VMR) Medical Concept Model Standard Medical Terminology uses depends on use 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 Action step If-then-else decision 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 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 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 1DM 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