Term list s vs snomed ct subset
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Term list(s) vs. SNOMED -CT ® subset. 2 nd 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

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Term list s vs snomed ct subset

Term list(s) vs. SNOMED -CT® subset.

2nd AAHA Software Vendors Summit – April 21, 2009

Lists of words
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 words1
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
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
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
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
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
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 history










Development history
Development history

  • SNOP

    • Morphologies


    • Morphologies, Etiologies, Locations


    • Same structure as SNOMED

    • Mix of existing SNOMED, additional veterinary content


    • Disorders, Morphology, Living organisms, social context

    • Veterinary content re-integrated


    • Logic based approach to SNOMED. Axes became hierarchies. Most significantly, the poly-hierarchic approach to classification.


    • SNOMED RT on steroids. Post merger with CTv3.

What do we get
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
Solution to synonymy

  • Obvious duplicates in AAHA draft list:


      • AAHA Category = Hematology, Lymphatic, Endocrine


      • 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
“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
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
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.

Functional subsets


“Cardiovascular disease” subset Algorithm



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
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
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
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
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 (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)


  • 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
AAHA terminology development

  • There is no “final version”

  • Walk don’t run

    • No syntax (post-coordination) just yet

    • Breadth first, depth later

Snomed extensions
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 extensions1
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
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
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 (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
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.