WhitePaper

CatherineStaesBSN,MPH,PhD

KeithCampbell,MD

Department of VeteransAffairs,VeteransHealth Administration (VHA)

Officeof InformaticsandAnalytics(OIA)

Knowledge Based Systems (KBS)

November12,2017

Fromretrospectivemappingtoprospectivestandardization:

Acomparisonofintegrationstrategiestoachievesemanticdatainteroperability

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Executivesummary

Background:Preservingthemeaningofinformationwhenexchangingelectronichealthrecorddata(i.e.,semanticinteroperability)iscriticalfordeliveringsafepatientcareandleveragingstandards-basedclinicaldecisionsupport.Giventhatindividualsoftenreceivehealthcarefrommorethanonehealthsystem,integrationofdatafrommultiplesourcesisneededto‘view’apatient’scompletehealthrecordandavoiderroneousclinicaldecisionsbasedonincompleteorinaccurateinformation,suchasdecisionsthatleadtoperformingunnecessarytestsorgivingapatientadrugtowhichtheyareknowntobeallergic.Todate,thestrategyforachievingsemanticinteroperabilitybetweentheclinicalsystemsoftheDepartmentofDefense(DoD)andtheVeteran’sAdministration(VA)hasbeento‘map’millionsofdataelementsusedintherespectiveEHRstostandardterminologies(e.g.,SNOMEDCT,LOINC,andRxNorm).‘Roundtriptesting’ofthemappedconceptshasidentifiedproblemswiththequalityofthemappingsforbidirectionaluse.Newstrategiesarerequiredtoachievesemanticinteroperabilitytosupportsafepatientcare,bothbeforeandafterthetwoorganizationsstartusingofasinglevendorfortheirelectronichealthrecordsystems.Theuseoflogicaldefinitionsandterminologysystemextensionstomanageconceptsusedinthedeliveryofcarecanovercomekeychallengeswiththemappingstrategy.

Objectives:Theobjectivesofthisreportareto:a)describethecurrentmappingapproach(i.e.,retrospectivemapping)andillustratecommonmappingscenariosthatresultinpoorqualitymappings,b)describeanewapproachforsemanticintegrationusinglogicaldefinitionsanddialectextensionstorepresentconceptsusedinthedeliveryofcare(i.e.,prospective/nativestandardization),andc)describetheimpactofthenewapproachontheproblemsobservedasaresultofthemappingstrategy.

Methods:Todescribethecurrentmappingapproach,wereviewedreportssubmittedbyaconsultingterminologyexpertwhoevaluatedtheprocessandoutcomesfromthemulti-yearmappingefforts,summarizedkeyfeaturesofthemappingmethodsthatthreatenquality,andidentifiedexamplestoillustratemappingchallenges.Todescribethenewapproach,weexplainthestrategyforrepresentingconceptsrequiredforinteroperability,internaluse,orintegrationofhistoricaldata,andwepresentbasicmodelsforrepresentingconceptsandmanagingrequestsfornewconcepts.Finally,weappliedthenewapproachtotheproblemsidentifiedfromthemappingstrategyanddiscussstrengthsandlimitations.

Results:Amajorthreattoqualityconcernedtherequirementthatlocalsourcetermsbemappedtoasinglestandardizedterminologyelement;nocreationoflogicalexpressionswasallowedtorepresenttargetconcepts.Thequalityofthemappingswerealsoimpactedbyincompleteanddifferentmappingrulesusedbythetwoorganizations.Ongoingresourcesarerequiredtoassessandmaintainmappingsovertime.

Thenewapproachtodataintegrationinvolvestheuseofdescriptionlogictomodelandmanageconceptsfromstandardterminologiestosupportclinicalcare.Insteadofmappinganexistinglocalcodeortermtoastandardcodewiththegoalofcreatingsemanticequivalence,challengescreatedbymappingwereavoidedbydirectlyrepresentingconceptsusingstandard

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codesorlogicalexpressionsthatconformtoadescriptionlogicmodel.Wedescribedthestrategyforrepresenting‘things’(i.e.meanings)aboutpatientcareusingexistingsingleSNOMED,LOINC,andRxNormconcepts,computablelogicalexpressionsbasedonSNOMEDCT,LOINC,orRxNormthatareaddedtoextensionsmanagedbyanorganization,organization-specificUUIDstosupportspecificlocalneeds,andbyadding‘names’(i.e.,newdialect-specificsynonyms)toalready-existing‘things’.Finally,‘alternateidentifiers’forSNOMED,LOINCorRxNormconceptsareusefulforintegratinghistoricaldatasosourceterms(linkedtoalternativeidentifiers)areaccuratelyrepresentedusingstandardconceptsdefinedusingdescriptionlogic.

Conclusion:Thenewapproachwillrequireadditionalexpertise,toolingandprocessestosupportthestrategy,butdeliversmanyadvantages,mostnotablyimprovedrepresentationof‘things’documentedduringclinicalcareandavoidanceofthechallengesderivedfromincompleteandvariablemappingrules.ThisstrategyisalignedwiththenewparadigmforelectronichealthrecordsfortheVAandtheDoD.Thisstrategyrequirescentralmanagementofterminologybutallowslocalizationtomeettheneedsofaparticularfacilityordomainofusers(e.g.nursing)andsupportsintegrationwiththelargevolumeofhistoricalinformationthatwillcontinuetobeimportanttoensuresafecaredelivery.

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TableofContentsExecutivesummary................................................................................................................1

TableofContents...................................................................................................................3

Background............................................................................................................................4Assessingreadinessofmappingsforbidirectionaluseforclinicalcare..............................................5

SuccessfulRoundTrip..........................................................................................................................6UnsuccessfulRoundTrip......................................................................................................................7

DescriptionLogic..............................................................................................................................8

Objectives..............................................................................................................................9

Comparisonofapproachesforsemanticintegration..............................................................9Interoperabilitythroughmapping.....................................................................................................9

Mappingapproachandchallengesofalarge-scalemappingproject..................................................9Observationsfromthemappingefforts.............................................................................................11

Informationlosswhenmapping(problemlistentryexample)......................................................................11Inappropriatemodel(CDSrecommendationexample).................................................................................12Variationinmappingbusinessrules(Allergenexample)...............................................................................13Variationandincompletemappingbusinessrules(Medicationexample)....................................................13Requirementsforqualityassessmentandmanagementofmappingsovertime.........................................14

Interoperabilityusinglogicaldefinitionsanddialectextensions.....................................................15Approachusinglogicaldefinitionsanddialectextensions.................................................................15Proposedsolutionstoproblemsobservedduringmapping..............................................................18

Informationlosswhenmapping(problemlistentryexample)......................................................................18Inappropriatemodel(CDSrecommendationexample).................................................................................18Variationinmappingbusinessrules(Allergenexample)...............................................................................20Variationandincompletemappingbusinessrules(Medicationexample)....................................................20Requirementsforqualityassessmentandmanagementofmappingsovertime.........................................21

AnticipatedChallenges.......................................................................................................................21

Summary...............................................................................................................................22Interoperabilitybymapping...........................................................................................................22Interoperabilitybylogicalexpressionsandsharedmodels.............................................................23Conclusion......................................................................................................................................24

References............................................................................................................................25

AppendixA.Datadomainsandtargetedstandardterminologiesusedwhenmappingbetweenthetwoorganizations.............................................................................................26

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Background

SemanticinteroperabilityofEHRdata(i.e.,theabilitytopreservethemeaningofclinicalinformationsharedbetweensystems)iscriticalfordeliveringsafepatientcareandleveragingstandards-basedclinicaldecisionsupport.Giventhathealthcareforanindividualisoftendeliveredbymorethanonehealthsystem,integrationofdatafrommultiplesourcesisneededto‘view’thecompletehealthrecord.Bi-directionalinformationsharingisnecessaryforcare-coordinationbetweenhealthcaresystemandtocommunicateinformationforclinicaldecisionmakingwhileavoidingerroneousclinicaldecisionsbasedonincompleteinformation,suchasdecisionsthatleadtoperformingunnecessarytestsorgivingapatientadrugtowhichtheyareknowntobeallergic.Thus,theprimarygoalofsemanticinteroperabilityispreservationofthemeaningofinformationforbidirectionaluse.

Toachieveinteroperability,heterogeneousclinicalsystemsmustunderstandboththestructure(syntax)andmeaning(semantics)oftheclinicalinformationbeingexchanged.Inotherwords,systemsmusthaveasharedunderstandingofa)themodelsusedtorepresentclinicalconcepts,andb)themeaningoftheconceptsincludedinthosemodels.Withoutthesetwofeatures,informationmaybeviewablebyhumans,butnotintegratedforviewingtrends,clinicaldecisionsupport,analysis,reporting,andotheruses.Forexample,theabilitytosharepatientdatausingawebbrowser,wherethesemanticsofthedataareinterpretedbythehumanwhoreadsthetextpresented,demonstratessyntacticintegration.EntriesinProblemListsfromtwosystemscanbeviewedtogether,butduplicatesorconflictinginformationcannotbeautomaticallyresolved.Interoperabilityrequiresharmonizationofdataonasemanticlevel.

Inthisreport,wedescriberesultsofalarge-scalemapping-approachtointeroperabilityundertakenbytwolargeUShealthcareorganizations.ThesetwoorganizationshavebeenmappingdataelementsusedintheirrespectiveEHRstostandardterminologies(e.g.,SNOMEDCT,LOINC,andRxNorm)asspecifiedbytheOfficeoftheNationalCoordinatorforHealthInformationTechnology(ONC).1Thegoalofmappingistotransformcontentbetweenasourceandatargetsystemtomeetthepurposefortheintegration.Morespecifically,mappingisdesignedtotransformclinicalmeanings(i.e.namesand/orcodes)usedinonehealthcaredeliverysystemintocodedclinicalmeaningsthatcanbeunderstoodbyahealthcaresystemusingadifferentschemeofclinicalmeanings(i.e.namesandcodes).Inotherwords,amappingallowsatargetsystemtounderstandclinicaldatageneratedbyasourcesystem.Sincethesetwoorganizationsbothprovideclinicalcareforoverlappingpopulationsofpatients,informationlossduringthetransformationprocesscanaffectpatientcareandisconsideredanunacceptableoutcome.Notethattransformationsforothermappingusecasesmayhaveahighertoleranceforinformationloss,particularlywhentheuseofthemappingsisuni-directional.Forexample,lossofinformationwhenclassifyingdiagnosesforbilling(i.e.,mappingSNOMEDCTtoICDcodes)doesnotimpactpatientsafety.

Theabilityofmappingeffortstopreservethemeaningofclinicalcontentdependsonmultiplefactors,including:

• thecontentdomain

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• thestandardterminologiesusedasthetarget

• theuseoflogicalexpressionstorepresenttargetmeanings(i.e.,bylinkingseparateconceptstorepresentasinglemeaning)

• theabilitytousemorethanoneterminologytorepresenttargetconceptsforadomain

Thesefactorsaresupportedbyfindingsfromthefollowingstudies:

• UsingSNOMEDCT,theproportionofsourceconceptswithexactmatchestoasingleSNOMEDCT(thetarget)conceptrangedfrom19-90%,dependingonthedomain;andlogicalexpressions(basedonmorethanoneSNOMEDCTconcept)wererequiredtoachieveanacceptablerepresentationinover40%ofthedomains.2

• 98.5%oftheclinicaltermssuggestedforaproblemlistcouldbeexpressedusingSNOMEDCT,buttheclinicaltermsrequiredthecreationofexpressionsanduseoflogicalmodels.3

• AcombinationofSNOMEDCTandRxNormsatisfiedmostcriteriaforencodingcommonallergiesandprovidedsufficientcontentcoverage.4

Thus,tosuccessfullyrepresentclinicalcontent,paststudieshaveshowntheneedtocreatelogicalexpressionsandintegrateterminologies(suchasSNOMEDCT,LOINC,andRxNorm).Onthebasisofthesestudies,aswellasotherpragmaticconcerns,weproposefoundinganInformaticsArchitectureuponadescription-logicbasedintegrationofSNOMEDCT,LOINCandRxNORM(i.e.,SOLOR),whichenablesthecreationoflogicalexpressionswhennecessarytoaccuratelyreflecttheintendedclinicalsemantics.Logicalexpressionscanbeusedtorepresentthemeaningofconceptswithformaldefinitions,allowingadescriptionlogicclassifiertoalgorithmicallydetectconceptequivalenceandidentifysubtypes(i.e.,‘children’oftheconcept).Theclassificationresultsandconceptdefinitionscanthenenablepatientandpopulation-basedinferencingrequiredforclinicaldecisionsupport.Incontrasttothe“mapping”strategyforinteroperability,whichattemptstocorrelatemeanings(namesand/orcodes)betweensystemsas‘exact’orinexact(i.e.,broaderthanornarrowerthan)matches,theuseoflogicalexpressionsallowsforexactrepresentation(i.e.,preservation)ofthemeaningofclinicalcontent.

TheSNOMEDCTConceptModelprovidesformaleditorialguidanceforstructuringdescription-logicbasedconceptdefinitions(i.e.,logicalexpressions)usingSNOMEDCTconceptstospecifyIS-Arelationshipsandattributes.ThisapproachisalreadybeingusedtointegratedomainsinLOINCwithSNOMEDCT.5Weadvocateusingthissameconceptdefinitionapproachforenablingsemanticinteroperabilitybetweenclinicalsystemsandcombiningthesedefinitionswithastandardizedobservationresultmodel,aswellasstandardmodelsofgoals,requests,andactions.

Assessingreadinessofmappingsforbidirectionaluseforclinicalcare

Bidirectionaluseofmappingsrequiresthattheclinicalmeanings(i.e.namesand/orcodes)usedinonehealthcaredeliverysystemcanbeunderstoodbyahealthcaresystemusinga

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differentschemeofclinicalmeanings(i.e.namesandcodes).Assessingreadinessrequiresanunderstandingoftherelationshipbetweenlocalcodes(names),standardcodes(concepts),andthe‘things’thecodesarerepresentingthatpertaintoclinicalcare(Figure1).

Figure1.Keycomponentsofthesemiotictriangle6

Inthesituationwheretwoorganizationshaveequivalent‘things’thatneedtobeshared,roundtriptesting(RTT)canbeusedtoassessthereadinessofmappingsforbidirectionaluse.RTTassessesuseofstandards-basedmappingacrossorganizationsbydomainandstandard,wherethestandardcodemediatesthelocalcodes.Tobesuccessful,exactmappingsmustbesharedbetweenthetwoormoreorganizations.Exactmatchesbetweenorganizations’mappingscanonlybeobtainedif:a)thetwoorganizationsarerepresentingthesame‘thing’,andb)astandardcodeexiststorepresentthe‘thing’,andthatcodeisusedforthemappings.Ifthesecriteriaaremet,thenthefollowingbidirectionalusecanbesupported:

Inthesituationwheretwoorganizationsarerepresenting‘things’thataredifferentinbreadthandlevelofgranularitywithrespecttoeachother,thenexactlymatchedconceptswillnotbeavailablefromtheorganizations.Forexample,organizationsoftenusedifferentgranularityandbreadthfordocumentnames.Inthissituation,standardcodesandexpressionswithdefinitionalknowledge(suchas,documentnameX‘is-a’childofdocumenttypeY)cansupportaggregationandunderstandingofthemeaningofthedocumentnamesshared.However,roundtriptestingisnottheappropriatemethodforassessingthequalityofmappingsbecauseequivalent‘things’don’texistbetweenthetwosystems.

SuccessfulRoundTrip

Successfulroundtriptesting(RTT)occurswhen:

• localcodesfromdifferentorganizationsthatrepresentthesame‘thing’(i.e.,havethesamemeaning)aregivenanexactmaptotheidenticalstandardcode.

ThefollowingscenarioillustratessuccessfulRTT(Note:similarcolorsrepresentexactmatches):

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UnsuccessfulRoundTrip

Unsuccessfulroundtriptestingoccurswhen:

• Localcodesfromdifferentorganizationsthatrepresentthesame‘thing’(i.e.,havethesamemeaning)areNOTgivenanexactmaptotheidenticalstandardcode.

Thefollowingscenarioscontributetounsuccessfulroundtriptesting:

• Errorsexistinamappingfile(e.g.,transcriptionerrorsortransposedmappingfileentries).

• Organizationsshareacommon‘thing’butindependentlymaptheirlocalcodesforthat‘thing’toadifferentstandardcode.Inthisexample,localcodesforequivalent‘things’aremappedtodifferentyetarguablyplausiblycorrectstandardcodes.

• Differencesininformationmodelsleadtodifferencesinthestandardcodesselectedforthemappings.

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• Differencesinthebreadthand/orlevelofgranularityoflocalcodesusedbyorganizationscomparedtotheavailablestandardcodescreatestheopportunityfordifferentstandardcodestobeselectedwhenmapping.Ifalocalcodeismorespecificthanthatofthecodesofferedinastandardterminology,thenthelocalcodemaygetmappedtoa‘broaderthan’standardcodes.Inthesituationpresentedbelow,thetwolocalcodesrepresentthesamemeaning,buttheexactmeaningisnotcurrentlyrepresentedbyasinglecodeinSNOMEDCT.Therearetwostandardcodesthatare‘broaderthan’thelocalcodes,eitherofwhichcouldbeselectedduringamappingeffort.Inthisscenario,thetwoorganizationsmappedtodifferent‘broaderthan’codes.

DescriptionLogic

Tomeetnationalgoalsfordatasharing,organizationsmustbeharmonizedtotheONC’sselecteddatastandards,mainlySNOMEDCT,LOINCandRxNORM.TheseterminologieswillberepresentedinSOLORwhichhasdescriptionlogiccomponentsthatallowforanewapproachtoharmonizationandtheabilitytosharepost-coordinatedexpressions.

Descriptionlogic(DL)usesaformalknowledgerepresentationlanguagetomodel‘concepts’(classes)and‘roles’(properties)andtheirrelationships,andiswidelyusedforcreatinglogicaldefinitionsofterminologycontent.Theformalsemanticsallowshumansandcomputersystemstoexchangedatawithouttheambiguitycreatedbymapping.Theformalsemanticsalsomakesitpossibletouselogicaldeductiontoinferadditionalinformationfromthefactsstatedexplicitlyandcomputably.ThisinferencecapabilityisanimportantfeaturethatdistinguishesDLsfromothermodellinglanguagessuchasUML.7

ThecapabilityofinferringadditionalknowledgeincreasesthemodellingpowerofDLsbutitalsorequiresthatthemodelerunderstandshowtouseDLand,aboveall,hasgoodtoolsupportforclassifyingcontentandcomputingconclusions.7ThecomputationofinferencesiscalledreasoningandanimportantgoalofDLlanguagedesignhasbeentoensurethatreasoningalgorithmsofgoodperformanceareavailable.7SinceDLconformstotheWebOntologyLanguage(OWL)EL2profile,existingorproposedtoolingcanbesharedtomanage,classify,andqueryknowledgerepresentedusingDL.

SNOMEDCTusesdescriptionlogictorepresentformal,computableconceptdefinitions.

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SNOMEDCTconceptsarebasedontheSNOMEDCTconceptmodelandhaverelationships(‘is-a’,‘attribute’)andattributeswithvaluesthatarebothdefiningandqualifying.Inaddition,theSNOMEDCTmodelincludeshierarchiesfordomainsofcontentandspecifiestheallowableattributesforeachdomain.Forexample,conceptsinthe‘Clinicalfinding’hierarchymayincludeattributessuchas‘Findingsite’,‘Dueto’,‘Severity’,andsoforth.Conceptsinthe‘Evaluationprocedure’hierarchymayincludeattributessuchas‘Component’,‘Measurementmethod’,andsoforth.Clincalcontentcanberepresentedaseithersingleconceptsorlogicalexpressions.SingleconceptsuseasingleSNOMEDCTconceptidentifier;andlogicexpressionshaveauniqueidentifierbutcontainmorethanoneSNOMEDCTidentifier.

Objectives

Theobjectivesofthisreportareto:a)describethecurrentmappingapproach(i.e.,retrospectivemapping)andillustratecommonmappingscenariosthatresultinpoorqualitymappings,b)describeanewapproachforsemanticintegrationusinglogicaldefinitionsanddialectextensionstorepresentconceptsusedinthedeliveryofcare(i.e.,prospective/nativestandardization),andc)describetheimpactofthenewapproachontheproblemsobservedasaresultofthemappingstrategy.

Comparisonofapproachesforsemanticintegration

Tobetterunderstandthevalueofsemanticintegrationusingdescriptionlogic,itisusefultoreviewtheprocessesandoutcomesofalarge-scalemappingproject.Themappingapproachwillthenbecontrastedwiththealternativeapproachofcodingclinicalinformationeitherdirectlyusingstandardcodesorbycreatinglogicalexpressions(i.e.,descriptionlogicdefinitions)usingstandardcodes.Thelatterapproachis‘nativestandardization’.

InteroperabilitythroughmappingMappingapproachandchallengesofalarge-scalemappingproject

Inthisreport,wedescriberesultsofalarge-scalemapping-approachtointeroperabilityundertakenbytwolargeUShealthcareorganizations.ThesetwoorganizationshavebeenmappingdataelementsusedintheirrespectiveEHRstostandardterminologiesinordertoenableinteroperability.ThetwoorganizationsfollowedmappingprocessesandguidancereceivedfromaCoordinatingOffice.TheCoordinatingOfficeselectedthedomainsofcontenttobemappedandspecifiedthestandardcodestobeusedbasedonguidancefromtheOfficeoftheNationalCoordinatorforHealthIT(ONC)(AppendixA).TheCoordinatingOfficedefinedmappingrulesandsetpriorities,andworkedwiththetwoorganizationstoreviewand‘sign-off’onthemappings.Eachorganizationcarriedoutitsmappingprojectindependently,butfollowedthesameoveralloperatingandqualitycontrolproceduresandweregiventhesamesetofdomainsandpriorities.Bothorganizationsusedteamsthatinvolvedamixofinternalandcontractedpersonnel.Whilethereweresimilaritiesinthemappingwork,therewerealsoimportantdifferences(Table1).8

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Table1.Descriptionofselectedfeaturesofthemappingeffortimplementedbytwoorganizations

OrganizationA OrganizationBContenttobemapped

~80,000localcodes/terms(i.e.potentiallyhighergranularity)

~12,000localcodes/terms(i.e.,potentiallylessgranular)

Tooling Usedamixtureoftooling(LEAP,RxNav),UMLStables,andmanualprocesses

Usedsometooling(Clue,RxNav,Workbench,RELMA),butmostlyamanualprocess

Mappingrules

AppliedrulesdefinedbytheCoordinatingOffice(i.e.,singleconcepttarget)butcreatednewrulesfordomainsofcontent• Rulesvariedbydomain• Rulesevolvedovertime• RelationshiptypesNOTadded;they

mappedonlytotheclosestmatchattemptingtomakeanexactmatch

AppliedrulesdefinedbytheCoordinatingOffice(i.e.,singleconcepttarget)butcreatednewrulesfordomainsofcontent• Rulesvariedbydomain• Rulesevolvedovertime• Relationshiptypeswereadded,indicating

whetherthemappingwas‘narrowerthan’,‘broaderthan’,‘equalto’,‘unmappable’,ortaggedaslegacy,outofscopeorlowfrequency.

Thefollowingfeaturesofthemappingeffortdirectlyimpactedmappingquality:

• Localsourcetermsweretobemappedtoasinglestandardizedterminologyelement.Nocreationoflogicalexpressionswasallowedtorepresenttargetconcepts.Morethanonesourcetermcouldmaptoasingletarget;one-to-manymappingswerenotpermitted.

• OrganizationAmappedtotheclosestmatchedtarget,whileOrganizationBaddedarelationshiptypeof‘exact’,‘narrowerthan(NT)’,‘broaderthan(BT)’,or‘unmappable’,andtaggedothersaslegacy,outofscope,orinfrequent.

• Whilesometoolswereusedtoenablemapping,thespecifictoolsandtheirusedifferedbetweenthetwoorganizations,andmappingeffortswereoverwhelminglymanualprocesses.

• Toimplementthemappingandqualityassessmentprocedures,teamsdevelopeddomain-specificbusinessandmappingrules.Sometimes,

o rulesvariedbetweenthetwoorganizations.Forexample,mappingofallergenreactantsdiffered.Forexample,OrganizationAusedUMLSCUIstomapmedicationallergenstoRxNorm,andconsideredDrugclassesandnon-drugallergenstobeunmappable.Incontrast,OrganizationBmappedmedicationallergenstoRxNorm,DrugclassestoNDF-RT,andnon-drugallergens(foodorchemicals)toUNIIcodes.Similarly,oneorganizationappliedaruleforlaboratorytestnamesbasedonthefollowingassumptions:If“nospecimenisfoundinthesourcetermandanunspecifiedsourceisnotavailableinLOINC,maptomostcommonspecimenorserum/plasma(usebestclinicaljudgment)”and“ForMicrobiologyterms,whennomethodisindicatedinthesourceterm,thedefaultwillbetoculturewhenclinicallyprobable”.8

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o necessaryrulesweremissing.Forexample,mappingrulesformedicationsdidnotspecifywhichRxNormtermtypesshouldbeused.

Todate,thetwoorganizationshavemappedmillionsoflocalcodesandtermstostandardcodesusingtheapproachesdefinedabove.Whilesomeofthemappingsproducedsemanticallyequivalentstandardcodesforequivalent‘Things’,manyofthestandardcodesselectedwereeither“narrowerthan”,“broaderthan”or“unmappable”incomparisontothe‘things’theywererepresenting.Whileahighpercentageofeachorganizations’localtermscouldbemapped,one-wayandround-triptestingshowedlimitedsuccesswithsemanticinteroperability.PreliminaryresultsoftheRRTshowedsuccessrangingfrom9%fordocumentnamesto63%formedications.Inaddition,thepercentofmappingsmediatedbysharedcodeswaslowforseveraldomainsforthetwoorganizations:14LOINCcodesmediatedonly8.6%or40%ofdocuments,fiveLOINCcodesmediatedonly29.4%or45.5%ofvitalsigns,and5,731RxNormcodesmediatedapproximately63%or33%ofmedications.

Observationsfromthemappingefforts

Herewepresentspecificexamplesthatillustratetheimplicationsoftheapproachundertaken,particularlytherequirementtomaptoasingletargetcode,thatmayexplainthelimitedsuccessinsemanticinteroperability.

Informationlosswhenmapping(problemlistentryexample)

Currently,OrganizationAusesMEDCIN9foritsproblemlistentries.MEDCINisaninterfaceterminologythatsupportscomplexexpressionsthatcanbefullyrepresentedusingpost-coordinationofSNOMEDCTconcepts.Intheexamplebelow,thecliniciansinOrganizationAcanincludethestageofthecancerwhentheydocumentcanceronaproblemlist(Figure2).Thestageofcancermaybeimportantforcaremanagement,totriggerclinicaldecisionsupport,orforcohortidentification.Therefore,preservingthestageofthecancerwheninformationissharedbetweenOrganizationswouldbeimportant.Currently,SNOMEDCTdoesnothaveasingleconceptthatcombinesprostatecancerandagivenstageofprostatecancer.Currently,thestagesarerepresentedasseparate‘findings’thatmustbeassociatedwiththeprostatecancer(disorder).Inotherwords,asinglecurrentSNOMEDCTcodecannotrepresentthefullmeaningof“prostatecancerstageIIB”.

Incontrast,atOrganizationB,mappingisavoidedbecauseonlysingleSNOMEDCTcodedtermsarecurrentlyallowableintheproblemlist.Whilethiscurrentpolicymaysimplifythemappingtask,cliniciansmayprefermoreexpressivetermswhenupdatingapatient’sproblemlist.ThewidespreaduseofMEDCINmaybeevidenceoftheneedforexpressive‘problems’or‘healthissues’.

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Figure2.SingletargetmappingsproposedforprostatecancerProblemListentries

Thefrequencyofadverseclinicaloutcomesduetothesekindsofmappingerrorsisunknown;however,someadverseeventsrelatedtomappingerrorsareknowntohaveoccurredinthepastandfuturepreventableadverseeventscanbeexpectedifnochangeoccurs.Forexample,thereisapotentialsafetyriskifaveteran’spremalignantconditionismappedtoabenignconditioninhistransferrecords.Thiskindofinaccuratemappingcouldresultinaprovidernotreceivingpromptsforannualfollow-up,potentiallyleadingtopreventableadverseoutcomes.

Inappropriatemodel(CDSrecommendationexample)

Tomapthesourceterm“NeedforvaccinationhepatitisB”followingthesingletargetstrategy,themappingteaminitiallymadethedecisiontousethebroaderterm“Procedureneeded(situation)”.Subsequently,theCoordinatingOfficerecommendedusinganarrowerexistingSNOMEDCTterm(“RequirescourseofhepatitisBvaccination(finding)”)(Figure3).

Figure3.SingletargetmappingsproposedfortermsrepresentingtheneedforhepatitisBvaccination

Infact,neitherselectionisappropriatefordifferentreasons.“Procedureneeded(situation)”istoobroadandnon-specific,andthecurrently-existing“RequirescourseofhepatitisBvaccination(finding)”isnotmodelledaccordingtothecurrently-recommendedapproach.Thereareplanstoreviewthecurrent(finding)hierarchyandmoveconceptstothe(observableentity)or(situation)hierarchieswhereappropriate.Forexample,the(situation)hierarchyisusedforinfluenzavaccinationconcepts.Vaccinationsareproceduresthataremoreappropriatelymodeledinthesituationwithexplicitcontexthierarchywhichwouldallowforthecontextoftheprocedure(e.g.,needed,refused,ordone)tobeusedasanattribute.

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Usinglogicalexpressionsandthe(situation)hierarchyforvaccinerecommendationsisamoreextendableapproachthatlimitscombinatorialexplosion.Thisapproachcouldmeetneedsasnewvaccinesbecomeavailableornewsituationcontextsneedtobedocumented.Inaddition,thisapproachcouldimprovealignmentwiththeintentofthesourceconcept,whichmayinfactberecommendingasingledoseofvaccine,nota3-dosecourseofhepatitisBvaccine.

Variationinmappingbusinessrules(Allergenexample)

AsdescribedinTable1,thetwoorganizationsfolloweddifferentrulestomapallergens.OrganizationAusedUMLSCUIstomapmedicationallergenstoRxNorm,andtheyconsidereddrugclassesandnon-drugallergenstobeunmappable(Figure4).Incontrast,OrganizationBdefinedmappingrulesthatalloweddifferentcodesystemstobeusedasthetarget.Forexample,medicationallergensweremappedtoRxNorm,drugingredientsweremappedtoRxNormorSNOMEDCT,drugclassesweremappedtoNDF-RT,andnon-drugallergensincludingfoodorchemicalsweremappedtoUNIIcodes.Asshowninfigure5,thedifferencesinthebusinessrulesbetweenthetwoorganizationsproduceddifferentresults.Accuratedocumentationofallergensiscriticalforpatientsafetybecauseadministrationofmedicationsorexposurestoproductsforwhichthepatientisalreadyknowntobeallergiccanresultinpreventableadverseevents,includingdeath.Informationaboutallergiesshouldbesharedbetweenclinicalsystemswherepatientsareseekingcare.MappableandknownallergensshouldnotremainunmappedandunavailableforprocessingbyCDSsystems.

Figure4.Samplemappingsofallergensproducedbydifferentmappingbusinessrules

Variationandincompletemappingbusinessrules(Medicationexample)

Thebusinessrulesformappingmedicationsvariedbetweenthetwoorganizations.AtOrganizationA,thet e am wa s i n s t r u c t e d t o mapmedications toanexactorslightlybroadertargetinRxNorm.Theywereinstructedtouseagenerictarget,butifthesourcehadtextforabrandname,thenusethebranddrugforthetarget.8Incontrast,atOrganizationB,exactmapsweredoneifthesourcetermhadanexactmatchtoanRxNormterm.IftherewereslightdeviationsinthesourcetextbutanequivalentmatchwasnotfoundinRxNorm,anoteof“notanexactmatch”wouldbeincluded.8

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Thebusinessruleswerealsoincomplete.Neitherorganizationwasinstructedtousespecifictermtypesfortargetcodes,eventhoughonlyfourtermtypeswouldbeappropriateforrepresentingprescribeddrugs(SemanticClinicalDrug(SCD),SemanticBrandedDrug(SBD),GenericPack(GPCK),andBrandNamePack(BPCK)).Table2showsasampleofmappingsproducedbyoneoftheorganizations.IfTermTyperuleshadbeeninplace,thetargetusingaSemanticClinicalDrugForm(SCDF)wouldnothavebeenallowed.

Table2.Sampleofmedication-relatedmappingsoutputfromtheprocess

Giventhepotentialsafetyrisksassociatedwithexchanginginformationaboutmedications,itiscriticalthatmappingsbeaccurate.AccuratelyrepresentingtheclinicaldrugorthebrandeddrugismoreimportantthannormalizingthetermtypeofSCDbecausethegraphofRxNormconceptscanbetraversed.Manuallymappingdrugnamescanposeasafetyriskgiventhelexicalchallengeposedbydrugnamesthataresimilartoeachotherandunfamiliartothepersonneldoingthemappings.Manualmappingrequiresexpertiseandformalprocesses,measurementsofreproducibility,anddemonstrationsofcompliancewithrelevantstandards.10Itisdifficulttotrainorfindpersonneltoperformmappingsiftheydonotyethaveaclinicalorpharmacybackground,andpersonswiththeneededclinicalorpharmacybackgroundmaybecostlytohire.Forexample,ifthedrugmetroprololinonehealthsystemweretobemappedtomethotrexatebyanothersystem,apatientmayreceivethewrongdrugwhenpresentingtoapharmacytopickuparenewal.Thesekindsoflexicalchallengesareknowntocausehumanerrorswhenprescribingordispensingdrugs,sotheneedforhumanjudgementtoperformmappingaddsyetanotheropportunityforerror.

Requirementsforqualityassessmentandmanagementofmappingsovertime.

Themappingprocessresultsinthecreationoffileslinkingsourcecodestotargetcodesthatwereknowntoexistatthetimethemappingtaskwascompleted.Terminologyisnotstatic,however.Newversionsofterminologycodesystemsarepublishedtwiceayear(SNOMEDCT,LOINC),monthlywithweeklyupdatesfromtheNLM(RxNorm),oratotherintervals.Anewversionmayaddnewcontent(forexample,leafstoanexistingSNOMEDCThierarchy)ormaycorrectaproblemthatshouldtriggeraninvestigationofapreviousmapping.Similarly,localtermsareregularlyaddedforuseinelectronichealthrecords,andthenewlocaltermswillrequiremappingstosupportinteroperability.Ifthenewly-releasedcontentiscorrectingaproblemrelevanttotheexistingmappings,oraddressespreviously-mappedcontent,thenmappingsmustbeupdated.

Currently,mappingsareupdatedinresponsetosystemupdatecycleswhichmayormaynotcorrespondwithupdatestotheunderlyingterminologysystem.Inaddition,quality

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managementprocessesdonotusuallyincludeongoingsurveillanceandregressiontestingasupdatesoccur.Safetyofthemappingscouldbeaddressedbyadoptingprinciplesfromaninternationalstandard,‘IEC62304Medicaldevicesoftware–Softwarelifecycleprocesses’.10Thisstandardspecifieslifecyclerequirementsforthedevelopmentofmedicalsoftwareandsoftwarewithinmedicaldevices,whichisapplicableforthemanagementofterminologyusedinelectronichealthrecords.Thestandardprovidesa“frameworkoflifecycleprocesseswithactivitiesandtasksnecessaryforthesafedesignandmaintenanceofmedicaldevicesoftware.”10Thestandardcallsouttheneedforriskanalysis(systematicuseofavailableinformationtoidentifyhazardsandtoestimatetherisk),riskcontrol(processinwhichdecisionsaremadeandrisksarereducedto,ormaintainedwithin,specifiedlevels),andriskmanagement(systematicapplicationofmanagementpolicies,procedures,andpracticestothetasksofanalyzing,evaluating,andcontrollingrisk).Inthecontextofmappings,QAresourcesshouldbeappliedbasedontheprobabilityandtypeofsafetyrisk(e.g.,fatalvsnon-fatal)associatedwiththeconceptsbeingmapped.Forexample,mappingsassociatedwithpotentiallyhighriskchemotherapydrugsshouldrequiremorequalityanalysisthanmappingassociatedwithlowerriskmoisturizingskinlotions.

Whileprocessescanbeimplementedtomanageriskandqualityassessmentsandthetasksforupdatingexistingmappings,theeffortassociatedwiththemappingactivitycouldbeavoidedaltogetherifstandardterminologies,suchasSNOMEDCT,LOINC,andRxNorm,wereusednativelytodocumentcare.Thechangesintroducedinthenewversionoftheterminologywouldbedirectlyappliedandavailableforuse.

InteroperabilityusinglogicaldefinitionsanddialectextensionsApproachusinglogicaldefinitionsanddialectextensions

Incontrasttomapping,analternativeapproachtodataintegrationinvolvestheuseofdescriptionlogic(DL)tomodelandmanageconceptsfromstandardterminologiestosupportclinicalcare.Wecallthisapproachprospectivestandardization.Insteadofmappinganexistinglocalcodeortermtoastandardcodewiththegoalofcreatingsemanticequivalence,severalofthechallengescreatedbymappingcanbeavoidedbydirectlyrepresentingconceptsusingstandardcodesorlogicalexpressionsthatconformtoadescriptionlogicmodel.11

Goingforward,theterminologyavailablefordocumentingcarecanbebasedonthefollowingstrategies:

A. Represent‘things’(i.e.meanings)aboutthecareofthepatientsthatarewidelyusedandrelevantforinteroperabilityusing:• existingsingleSNOMEDCT,LOINC,andRxNormconcepts• computablelogicalexpressionsbasedonSNOMEDCT,LOINC,orRxNormthatare

createdandaddedtoextensionsmanagedbyanorganization.B. Represent‘things’onlyofinternalvalue(i.e.notrelevantforinteroperability)using

Organization-specificconceptsthatarecreatedtosupportaspecificlocalneed.

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• Anorganization-specificUUID(UniversallyUniqueIdentifier)canbeusedforconceptsthatarerelevantforadministrativeorbillingdecisionsthatdonotimpactdirectpatientcare.Forexample,whenadministrativepersonnelneedtocalculatearatingforeatingdisorders,theyneedtoselectamongasetofcomplexconceptstogeneratearatingscore,suchas:“Self-inducedweightlosstolessthan80percentofexpectedminimumweight,withincapacitatingepisodesofatleastsixweekstotaldurationperyear,andrequiringhospitalizationmorethantwiceayearforparenteralnutritionortubefeeding”.Thisinformationisderivedfromreviewoftheclinicalrecord,butthegoalisnottostorethisinformationbackintotheclinicalrecordasafully-specifiedconcept.

Inadditiontoneedingconceptstorepresent‘things’,sometimesthereisaneedforadditional‘names’(forexisting‘things’inastandardterminology)tobeavailableasaninterfaceterminology.Forinstance,historically-usedtermsmaynotbepresentinastandardterminologybutmaybepreferabletoagivenorganization.Tomeetthisneed:

C. Addadditional‘names’toalready-existing‘things’.Newdialect-specificsynonymscouldbeaddedtoanexistingconcepttomeettheneedsofinterfaceterminologysystems(e.g.,nursingterminologies,patientfriendlyterminologies,andsoforth).Forexample,ifanorganizationhasapreferreddialectof‘femurfracture’over‘fractureoffemur’,thenanewsynonymcanbeaddedtothecurrentconcept‘Fractureoffemur(disorder)’(Figure5).

Theabovestrategiesaddressstandardizationgoingforward,butmaynotaddressalltheneedstostandardizeexistingrecordstoensurehistoricalinformationisavailableforclinicaldecisionsupport,integratedviewsandanalysis,andpopulation-levelreporting.Therefore,retrospectivestandardizationmayberequiredtohandleexistingsourceconcepts,particularlywhenyoucareaboutsemanticequivalence,butdonotneedtoaddasynonym.Tosupportthisneed,

D. Add‘alternateidentifiers’toSNOMEDCT,LOINC,orRxNormconceptsorexpressionsbuiltusingSOLORtooling.Thisstrategyisusefulforintegratinghistoricaldatasosourceterms(linkedtoalternativeidentifiers)areaccuratelyrepresentedusingstandardconceptsdefinedusingdescriptionlogic.Anyexistinglocalcodecanbeaddedasanidentifier,thuslinkingthelocalcode’suniqueIDtotheSNOMEDCTconceptID.Thisapproachwillonlyworkifthelocalidentifieradherestoconceptpermanencedesiderataprinciples(i.e.,themeaningwillnotchangeovertime).• Forexample,asshowninFigure5,anewalternativeidentifiercorrespondingtothe

sourcesystemidentifiercouldbeaddedtothecurrentconcept‘Fractureoffemur(disorder),butnonewdescriptionisnecessaryiftheexistinglocal‘name’doesnotneedtobedisplayed.

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Figure5.SnippetofaSNOMEDCTConceptwithanewAlternativeIdentifierandSynonym.

Thisapproachhasseveraladditionalstrengths.First,agenericstrategyisbeingusedtohandleeachsituationdescribedabove,supportingsoftwarereuseandavoidingaccidentalcomplexitybydevelopingsimilarbutdifferentstrategiesforsimilarprocesses.AdescriptionoftheprocessforhandlingnewrequestsisshowninFigure6andthebasicmodelforrepresentingconceptsinshowninFigure7.Second,overtime,anorganizationcantransitiontousethenewcontentinlieuoftheoriginalnon-nativecontent.Anorganizationcanidentifycoreinformationrequiredforinformationexchange,decisionsupportandreportingneeds,andprioritizetheseneeds.Third,thisapproachwillcontributetothecommunityandhelpSNOMEDCTevolve.SNOMEDCTdoesnotbenefitandevolvefrommappingefforts.

Figure6.Processforhandlingtherequesttoaddanew‘thing’toaterminology

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Figure7.Basicmodelforrepresentingconceptsintheterminology

Proposedsolutionstoproblemsobservedduringmapping

Theuseofdescriptionlogicandlogicalexpressionsallowssourceconceptsthatarerepresentedinastructuretobemorecompleteincontent,morecorrectinmeaning,andmoreconsistentinrepresentation.IfbothOrganizationAandOrganizationBrepresenttheircontentusingalogicalexpressionmodel(suchasprovidedbytheSNOMED/LOINCintegrationeffort5),thecontentcanbeintegrated.

Hereareexamplesofhowtheproblemsdescribedabovecanbeaddressed:

Informationlosswhenmapping(problemlistentryexample)

ToovercomethedatalossthatoccurswhenselectingasinglecurrenttargetSNOMEDCTcode,eithernewly-definedsingleconceptswithalltherequiredsemanticscanbeaddedtoanorganization’sextension,orlogicalexpressionscanbedefinedfollowingbusinessrules.Eitherway,thegoalistocreatecomputablelogicalexpressionsusingthenativestandardsandtoprovidetheclinicalmeaningsrequiredforclinicalcare.MissingcontentcanbeaddedtoanOrganization’sextension,butcontentdevelopmentbusinessrulesshouldbedevelopedandfollowed.

Inappropriatemodel(CDSrecommendationexample)

Thereisanalternativetomapping“HepatitisBvaccineneeded”toasingletargetcoderesultingintheerroneousselectionofaconceptthatistoobroad(“Procedureneeded(situation)”)orthatismodelledincorrectly(“RequirescourseofhepatitisBvaccination(finding)”).Thealternativewouldbetoeithercreateasingleadditionalconceptthatexpressesalloftherequiredsemantics,andaddittotheorganization’sextensionofSNOMEDCT(figure8);orrepresenttheconceptusingalogicalexpression(Figure9).Thesetwooptionsareillustratedinthefiguresbelowasmock-upsinademonstrationenvironmentandarenotintheSNOMEDCTInternationalRelease.Withthisstrategy,thesourcetermhascompleterepresentationasaSNOMEDCTlogicalexpressionanditsDLcomponentscanberepresented

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withintheformalontologicalstructure.TherewouldbenodatalossfromOrganizationA’sMEDCIN-basedtermsandtheconceptwouldnowbeavailableforOrganizationBaswell.

Figure8.Mock-upofasingleconceptwithalltherequiredsemanticsneededfor“HepatitisBvaccinationneeded(situation)”

Figure9.Mock-upoflogicalexpressionsfor“HepatitisBvaccinationneeded(situation)”

ThisstrategyisconsistentwithtwocurrentSNOMEDCTconcepts(“Influenzavaccineneeded(situation)”and“Anti-Dglobulinneeded(situation)”),andthemodelusedtodocumentthathepatitisBvaccinationisdone(Figure10).Usingthestructuresillustrated,amodelercouldreplacetheProcedurecontext(attribute)of‘needed’withanattributeof‘Refused’or‘Done’,orcanreplacetheAssociatedProcedure(attribute)withanewvaccine.Thisstrategyofusinglogicalexpressionsisextendableandavoidsthecombinatorialexplosionthatcouldoccurifsingle-conceptsforeveryvaccineandcontextweretoberepresentedbyasingleSNOMEDCTcode.Inaddition,thisstrategysupportstheuseoftemplatesfordefiningnewconceptsrequiredforaninterfaceterminology.

express‘HepatitisBvaccinationneeded(situation)’===243796009|Situationwithexplicitcontext(situation)|:{363589002|Associatedprocedure(attribute)|=16584000|HepatitisBvaccination(procedure)|,408730004|Procedurecontext(attribute)|=410525008|Needed(qualifiervalue)|,408731000|Temporalcontext(attribute)|=410512000|Currentorspecifiedtime(qualifiervalue)|,408732007|Subjectrelationshipcontext(attribute)|=410604004|Subjectofrecord(person)|}===417451006|Procedureneeded(situation)|:{363589002|Associatedprocedure(attribute)|=16584000|HepatitisBvaccination(procedure)|,408730004|Procedurecontext(attribute)|=410525008|Needed(qualifiervalue)|,408731000|Temporalcontext(attribute)|=410512000|Currentorspecifiedtime(qualifiervalue)|,408732007|Subjectrelationshipcontext(attribute)|=410604004|Subjectofrecord(person)|}

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Figure10.Semanticsusedtodescribe“HistoryofHepatitisBvaccination(situation)”

Variationinmappingbusinessrules(Allergenexample)

Domain-specificrulesformappingwillnolongerbenecessary.Instead,themajorityoftheconceptsrequiredwillbeavailablefromjustthreecorecodesystems(SNOMEDCT,LOINC,andRxNorm)thatareintegratedandmanagedusingdescriptionlogicandSOLORtooling.AllergensforspecificmedicationscanberepresentedusingRxNorm;allotherallergens,includingclassesofmedication,canberepresentedusingSNOMEDCT(Figure10).Eachofthelocalcodes(e.g.,OrganizationAcode4849001andOrganizationBcode4538707forCephalosporin)couldbeaddedtotheequivalentSNOMEDCTcodeasalternativeidentifierstoenableinteroperabilitywithhistoricaldata.Ifcliniciansrequiretheterm‘Cephalosporins’,ratherthanthecurrentSNOMEDCTpreferredtermof‘Cephalosporin-classofantibiotics’,thenanewsynonymcouldbeaddedandspecifiedasthePreferredterminfortheOrganization’sdialect.

Figure10.ExampleofallergensrepresentedinSNOMEDCTwithadditionalidentifiersandsynonymsintheextensiontosupportinterfaceneedsandintegrationofhistoricaldata.

Variationandincompletemappingbusinessrules(Medicationexample)

Businessrulesformappingmedicationnameswillnolongerbenecessary.Thisisimportantbecauseanymappingotherthanaone-to-onesimplerenamingofadrugconcepthasimportantpatientsafetyimplications.

Usingthenewstrategy,anexistingsourceconceptidentifiercanbeaddedinSOLORasanalternateidentifiertothesameconceptderivedfromRxNorm.Alternatedrugidentifiersare

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anticipatedtobecomelessimportantovertime,astheRxNormconceptsbecomepredominantintherecordandhistoricalmedicationinformationbecomeslessrelevantforapatient’scare.Inaddition,RxNormcontentcanbemanagedusingdescriptionlogic,whichwillallowforqueryingandclassificationfordecisionsupport,suchasallergycheckinganddrug-druginteractionchecking.

SinceRxNormdoesnotincludedrugclasses,drugclasseswillberepresentedusingSNOMEDCT,withsynonymsandalternateidentifiersassignedtoSNOMEDCTconceptswhereappropriate.

Requirementsforqualityassessmentandmanagementofmappingsovertime.

Qualityassessmentandmanagementofmappingfileswillnolongerbenecessaryasaseparateactivityfromterminologydevelopmentitself.Byeliminatingthismappingstep,wereducethecomplexityoftheoverallsystem,makingiteasiertoscaleandtovalidatecontent.Limitedresourcescanbeusedmoreefficiently.ThetasksassociatedwithmaintainingthequalityoftheterminologyavailablewillbeaddressedbytheproceduresalreadyrequiredformaintainingtheSOLORenvironmentandtheextensions.TheseprocesseswillneedtobeconformantwithIEC6230:2006Medicaldevicesoftware–Softwarelifecycleprocesses.9Whennativestandardsareused,thesynchronizationchallengeswithnewreleasesofterminologyassociatedwiththeuseofmappingfilescanbeavoided.

AnticipatedChallenges

Implementingthenewstrategywillhavechallengesthatinvolvepeople,tooling,andprocesses.Somehighlevelchallengesinclude,butarenotlimitedto,thefollowing:

• People:Tomodelconceptsanddefinetheassociateddescriptionlogic,personnelmust:a)havepracticalclinicalknowledge,b)haveanappreciationforlogicandformalreasoningthatarerequiredtocreateandmaintainthelogicalexpressionsthatformtheheartofthisapproach,andc)havecurrentknowledgeaboutcontinuallyevolvingSNOMEDCTpoliciesthatmayimpactdecisions.ThehighlearningcurveformodellinginSNOMEDCTcanmakeitchallengingtohire,train,andretainqualifiedstaff,particularlywithoutadvancedtoolingtosupportthiswork.Toolingiscriticalforsupportingthepeopleinvolved.

• Tooling:Asuiteoftoolsisrequiredtodevelop,manage,andmonitorthequalityofcontentovertime.Forexample,toolsareneededtocreate,edit,name,evaluate,andsearchforlogicalexpressionstosupportthisapproach.Whencreatingnewlogicalexpressions,modelerswouldbenefitfromtemplatestocreateexpressionsforpre-definedcontexts,suchas‘Procedureneeded…’,‘Historyof…’,andsoforth.Templatescanbeanassistivetoolthatenforcesmodelingrulesandsimplifiestheeditingtask.Toolingcansupporttheauto-generationofhumanreadablenamesforanewexpression,whichisparticularlyneedediftheexpressionisusedinaninterface.Aclassifierisrequiredtosearchforequivalentexpressionsinadatastore.Finally,toolsareneededtoauditandvisualizecontenttoidentifyerrorsorpatterns

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thatcanguidequalitymonitoringandtrainingpolicies.Forexample,dashboardscanassistwithearlyerrordetectionorthroughputandoutcomequalityassessment.Anytoolingneedstobeagiletoenableupdatesaspolicieschange.

• Processes:Processesarerequiredtoenforcereproducibility,minimizevariation,andincreaseefficiencywithmodeling.Standardprocedures,templates,andlogicalexpressionarchetypeswillneedtobedeveloped,documented,andusedtoensureaccuracyandconsistencyacrossmodelers.Definingtheboundarybetweenconceptsthatcanorcannotbedevelopedusingpredefinedtemplatesmaybeachallenge,butthisproblemcanbeaddressedthroughpracticalexperienceusingthisapproach.Enforcingreproducibilityisaprimarygoalthatcanbeachievedusinganiterativedualindependentreviewprocess12;butalternativestrategiesmaybedesignedtoachievethesameoutcomeatalowercost,particularlydependingonthetoolingavailable.Forexample,auditinformation(bymodelerandoutcome)canguidepoliciesaboutthefrequencyandintensityofthereviewactivitiesrequiredamongthemodelingteammembers.Dualindependentreviewmaybenecessaryforcontentthatiscomplex;whereas,highly-templatedcontentdevelopedbyanexperiencedmodelermayonlyrequireasecondreviewertocheckasampleofthemodelsdeveloped.Afterdevelopingcontent,processesarealsorequiredtomanagecontentandissuesthatariseovertime,suchas,possiblechangesinthemeaningofalternativeidentifiersusedassynonyms.

Goingforward,theseandotherchallengesmustbeacknowledgedandaddressed.

SummaryInteroperabilitybymapping

Achievingsemanticdataintegrationbywayofmappinglocalcodes/termsfromdifferentorganizationstoaconceptrepresentedbyasinglestandardcodefromanationally-acceptedstandardhashadlimitedsuccess.Potentialharmonizationhasbeenshownforalimitedsetoftermsforsomedomains(e.g.,medications)butalargeproportionoftheresultingmappingsarenotsemanticallycompatiblebetweenthetwoorganizations.Therequirementthatasingletargetconceptmustbeusedwhenmappingwillneverfullysatisfysemanticequivalenceforalldomains.Thelimitationsofthesingletargetandmanually-processedapproachadverselyaffectsdataquality,limitsdatasharingcapabilities,andmayposeapreventablesafetyrisk.

Mappingisaretrospectiveeffortatinteroperabilitythatwillalwaysbeoutofdateandintroducesnewopportunitiesforerrors.Theprocessresultsinthecreationofmappingfilesofsourceandtargettermsthataretobeusedtointerpretcodesexchangedbetweendepartments.InTable3,wepresentexamplesofchallengeswhenmappingthatimpactcorrectness,completeness,consistency,andtimeliness,anddescribepotentialsolutions.

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Table3.Potentialproblemsobservedoridentifiedduringmappingeffortsandpotentialremediationstrategies

Mappingchallenge PotentialremediationstrategyHumansubjectivityintroducedwhenselecting‘broaderthan’,‘narrowerthan’,or‘closestmatch’(impactscorrectness)

Allowcomputablelogicalexpressions,ratherthanasingletargetconcept,todefineasourceterm

Informationislostwhenasingletargetisrequired,andnoequivalenttargetcodeexists(impactscorrectness)

Allowcomputablelogicalexpressions,ratherthanasingletargetconcept,todefineasourceterm

Many‘unmappable’sourceconcepts(impactscompleteness)

• Allowcomputablelogicalexpressions,ratherthanasingletargetconcept,todefineasourceterm

• Createorganization-specificconceptsinSOLORusingDLandstandardmodelsandmanageintheextension.

Difficultyascertainingthedefinitionoflocalcodesandterms(impactscorrectness)

Defineeachconceptwithafully-specifiednameusingDescriptionLogictoclarifythedefinitionoftheconcept.

Asnewversionsofterminologyisreleased,mappingsmaybecomeoutofdatebecausemaintenanceofthemappingsandtheterminologyareseparatetasks.

Whenweusethenativestandardizationoption,terminologywillbemaintainedasasinglesystem.Thus,asnewversionsofterminologyarereleased,maintenancewillbehandledonce,nottwice.

Problemswithquality:consistency Usestandardterminologies,particularlythecoreofSNOMEDCT,LOINC,RxNorm

Mappingprocessundertakenindependentlybythetwoorganizations

Nativestandardizationavoidstheneedformapping

Mappingrulesvariedanddifferenttoolingused

Nativestandardizationavoidstheneedformapping

Interoperabilitybylogicalexpressionsandsharedmodels

Theuseoflogicalexpressionsandsharedmodelssupportinteroperability.Insteadofmappinganexistinglocalcodeortermtoastandardcodewiththegoalofcreatingsemanticequivalence,severalofthechallengescreatedbymappingcanbeavoidedbydirectlyrepresentingconceptsusingstandardcodesorstandards-basedexpressionsthatconformtoadescriptionlogicmodel.11

Goingforward(i.e.,forprospectivestandardization),theterminologyavailablefordocumentingcarecanbebasedon‘things’representedbyexistingsingleSNOMEDCT,LOINCorRxNormconcepts,orcomputablelogicalexpressionsbasedonconceptsfromthesecodesystems.Organization-specificconceptsthatarecreatedtosupportaspecificneed,butnotnecessaryforinteroperability,canbemanagedusingOrganization-specificUUIDs.Additional‘names’canbeaddedtoexistingconceptsusingthedialectfunctionalityinSNOMEDCT,tomeettheneedsofinterfaceterminologysystems(e.g.,nursingterminologies,patientfriendlyterminologies,andsoforth).Finally,‘AlternateIdentifiers’toSNOMEDCT,LOINC,orRxNormconceptsorexpressionsbuiltusingSOLORtoolingcanbeusedtointegratehistoricaldataso

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sourcetermsareaccuratelyrepresentedusingstandardconceptsdefinedusingDescriptionLogic.

Thisapproachhasseveraladditionalstrengths.First,agenericstrategyisbeingusedtohandleeachsituationdescribedabove,supportingsoftwarereuseandavoidingaccidentalcomplexitybydevelopingsimilarbutdifferentstrategiesforsimilarprocesses.Second,overtime,anorganizationcantransitiontousethenewcontentinlieuoftheoriginalnon-nativecontent.Anorganizationcanidentifycoreinformationrequiredforinformationexchange,decisionsupportandreportingneeds,andprioritizetheseneeds.Third,thisapproachwillcontributetothecommunityandhelpSNOMEDCTevolve.SNOMEDCTdoesnotbenefitandevolvefrommappingefforts.Thechallengeswiththisapproachcanbeaddressed.

Conclusion

Inconclusion,achievingsemanticinteroperabilitytosupportthesafedeliveryofclinicalcarerequiresachangeinstrategiesfrommappingtotheuseoflogicaldefinitionsanddialectsmanagedinanextension.

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AppendixA.Datadomainsandtargetedstandardterminologiesusedwhenmappingbetweenthetwoorganizations