WhitePaper
CatherineStaesBSN,MPH,PhD
KeithCampbell,MD
Department of VeteransAffairs,VeteransHealth Administration (VHA)
Officeof InformaticsandAnalytics(OIA)
Knowledge Based Systems (KBS)
November12,2017
Fromretrospectivemappingtoprospectivestandardization:
Acomparisonofintegrationstrategiestoachievesemanticdatainteroperability
WhitePaper:Achievingsemanticinteroperability
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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