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Term list(s) vs. SNOMED -CT® subset. 2nd AAHA Software Vendors Summit – April 21, 2009
Lists of words… • Nomenclature • The system or set of names for things • Vocabulary • A collection or list of words with explanations of their meanings • Classification • The result of classifying; a systematic distribution, allocation, or arrangement, in a class or classes; esp. of things which form the subject-matter of a science or of a methodic inquiry. (SNOMED)
Lists of words… • Terminologies are about information sharing, retrieval, aggregation and analysis. • It’s difficult if not impossible to justify the effort required to “do terminology right” from a data entry perspective. • A functional terminology must attend to both perspectives.
What do we need? • Nomenclature ONLY • Provides a simple list for data entry • Vocabulary / Classification • We can be CERTAIN that the “term” (description in SNOMED) means what we think it means. • We can develop rules that allow us to combine concepts to express ideas more complicated than those contained in the nomenclature. • We can use the knowledge base supported by the vocabulary/classification to search, retrieve and analyze our data.
Why a controlled nomenclature? • Aggregation of text-based content from multiple sources • Multiple individuals • Multiple institutions • Any time you rely on a computer to manipulate language and “meaning” is critical.
Why a controlled vocabulary / nomenclature? • Controlled vocabularies should automate recognition of and accurate substitution of synonyms. • Controlled vocabularies should facilitate retrieval and categorization.
Complaints about SNOMED • It’s too… • Big • Complicated • Expensive • Yes but… • We can make it smaller (sort of), and use small pieces (for most purposes). • Use it in simple and straightforward ways • But nothing, it’s expensive. • Not the license fees, the cost of making it work.
Why pick something as big and complicated as SNOMED? • Viable nomenclatures must be maintained. • SNOMED is the ONLY actively maintained nomenclature that has veterinary content. • Veterinary medicine CANNOT afford: • to build it’s own competent nomenclature • to continue to live without a competent nomenclature
SNOMED history SNOMED I & II SNOMED RT SNOMED CT SNOMED III SNOP SNOVET IHTSDO 2000 1965
Development history • SNOP • Morphologies • SNOMED • Morphologies, Etiologies, Locations • SNOVET • Same structure as SNOMED • Mix of existing SNOMED, additional veterinary content • SNOMED III • Disorders, Morphology, Living organisms, social context • Veterinary content re-integrated • SNOMED RT • Logic based approach to SNOMED. Axes became hierarchies. Most significantly, the poly-hierarchic approach to classification. • SNOMED CT • SNOMED RT on steroids. Post merger with CTv3.
What do we get ? • Sound technical solution to synonyms. • Ability to “localize” the synonyms • Compatibility with other “lists” • Ability to merge AAHA-based records with others (e.g., a cardiology specialty subset) • Functional Sub-setting • Enhanced queries
Solution to synonymy • Obvious duplicates in AAHA draft list: • HYPERGLYCEMIA, BLOOD GLUCOSE INCREASED • AAHA Category = Hematology, Lymphatic, Endocrine • HYPERGLYCEMIA, BLOOD GLUCOSE INCREASED • AAHA Category = Metabolic • (NOT) Obvious duplicates in AAHA draft list • Thyroid gland mass • AAHA Category = Hematology, Lymphatic, Endocrine • Mass, thyroid • AAHA Category = Neoplasm • In SNOMED, both = 237557003 = Mass of thyroid gland (finding)
“Local” Synonyms • It is POSSIBLE to allow practitioners to add their own favorite description of a concept. • Analysis / transmission by conceptID.
Compatibility with other lists • AAHA list can be part of “mixed animal” system • AAHA list would integrate (could be used to query) a more granular specialty list.
Functional Sub-setting • We only need PORTIONS of SNOMED • DIFFERENT portions of SNOMED needed for different contexts in HIS. • Retain the ability to use ALL of SNOMED to search, retrieve, analyze data produced using sub-sets. • Be prepared to transfer (copy) from SNOMED to subset as needs change.
FunctionalSubsets All of SNOMED “Cardiovascular disease” subset Algorithm Vet Subset Cardiovascular Diseases Intersection = Veterinary Cardiovascular Diseases
SNOMED Subset • “…a set of Concepts, Descriptions, or Relationships that are appropriate to a particular language, dialect, country, specialty, organization, user or context.” • “…simplest form, the Subset Mechanism is a list of SNOMED identifiers (SCTIDs).” • “…may be used to derive tables that contain only part of SNOMED CT.” • Can be selected by clever query, if underlying definitions in SNOMED are sound.
Existing Subset(s) • Non-human subset • This subset assists applications that desire to exclude concepts which are not human medical concepts (i.e., paw and fin). • Note that this is NOT a veterinary subset as that subset would include terms shared with humans such as brain and eye. • Pathology subsets (3) • CAP Cancer checklists • Allergen subsets
AAHA Subset(s) • SNOMED then remove hierarchies that are NOT of interest. • Someone has to decide what’s “not of interest” • Someone familiar with SNOMED • Someone with domain knowledge • Desired functionality • We think it’s important to distribute a subset of the hierarchy above the AAHA subset with relationships • Facilitate retrieval queries, may be possible to use the hierarchy to control “lists in correct context” (this does not currently exist.
Subset development (Ideal) • Build a competent Veterinary Subset of SNOMED • Veterinary subset a resource shared by the profession. • Managed by central “authority” • Distributed by SNOMED? • Use algorithm approaches to create “microsubsets”
What we’re doing instead… • Intellectual investment (by AAHA) in a list of terms representing desirable small animal medical content. • “Mapping” by VTSL and EHRTF • Add “missing” content through SNOMED Extension mechanism. • AAHA terms expressed as SNOMED descriptions. • Permanent identifiers
Mapping (why we didn’t just map AAHA’s list). • Mapping is directional • Largely the result of differing granularity between “target” and “source” • 1:1 – Concept is the same • Term may be identical or synonym – remember to distinguish on CONCEPT not on string • Narrow to Broad – Source concept is more specific than target • Broad to Narrow – Source concept is more general than target • Two maps may be needed for bi-directional functionality (unless entire map is 1:1)
Mapping • 1:1 maps will represent a majority • Broad (source) to narrow (SNOMED) • Good argument that SNOMED needs more content • Narrow (source) to broad (SNOMED) • SNOMED may need/want the content • Map to a post-coordinated concept may be required
AAHA terminology development • There is no “final version” • Walk don’t run • No syntax (post-coordination) just yet • Breadth first, depth later
SNOMED Extensions • Enable authorized organizations (VTSL maintains two namespaces) to add Concepts, Descriptions, Relationships and Subsets to complement those that are centrally maintained as the core content of SNOMED CT. • specialized terminology needs of an organization. • ISIS / ZIMS • USDA • FDACVM • Extensions maintain unique identification across organizations.
SNOMED Extensions • Distinguishable from the main body of SNOMED CT • in the thesaurus • when stored in a patient record, query or decision support protocol. • Distinguishable from other Extensions, in the same way as they are distinguishable from the main body of SNOMED CT. • Able to be distributed and processed in the same way as equivalent components from the main body of SNOMED CT without requiring specific adaptations of SNOMED-enabled applications.
Existing Extension(s) • US Drug extension • List of drugs marketed in the United States • Veterinary drugs have not been maintained in some time. • UK Drug extension
What are we doing to the AAHA Diagnostic Terms list? • Two reviews by VTSL veterinarians, third review by AAHA team. • Determining what each term MEANS • Mapping each term to SNOMED • Editing the terms • Slightly more natural English • Separating list of synonyms into individual descriptions • Limiting commas to one “use” only • Converting to sentence case • Providing SNOMED identifiers for each description
AAHA Terms (version changes) • AAHA terms will have SNOMED-based identifiers • AAHA terms will be mapped to SNOMED concepts • Phrasings more like natural English • Only one use of commas • “Within-term” synonyms will be separate descriptions.
Future project(s) • Plan / build user request system • Characterize AAHA content • Patient findings • Laboratory findings • Morphologies • Add, then “clean up” upper hierarchy • Hierarchy to display "in appropriate context" • (Liver things show up when vet wants liver things). • Create similar specialty-based subsets • Increased specificity/granularity • Cardiology, Neurology, etc.