1. Overview of SNOMED CT International Release, U. S
Overview of SNOMED CT International Release, U.S. Extension of SNOMED CT and NLM SNOMED Resources Everything (more than) you wanted to know about SNOMED CT
James T. Case MS, DVM, PhD
Health Program Specialist – SNOMED CT
National Library of Medicine
Bethesda, MD

2. Lists of words… Terminology Nomenclature Vocabulary Classification
The body of specialized words relating to a particular subject
Nomenclature
The system or set of names for things, etc., commonly employed by a person or community (ICD-9, CPT, HL7 Tables, SNOMED CT)
Vocabulary
A collection or list of words with explanations of their meanings (HL7 Tables, SNOMED CT)
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. (ICD-9)

3. When do you need 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.
Test lists (for comparability)

4. Why did “we” pick SNOMED CT?
A shared nomenclature must be maintained.
SNOMED is the ONLY actively maintained reference nomenclature that addresses public health content.
NLM/CDC has a long-term investment
Public Health CANNOT afford:
To build it’s own competent nomenclature
To continue to live without a competent nomenclature

5. Characteristics of a controlled vocabulary / nomenclature.
Cimino, JJ. Desiderata for Controlled Medical Vocabularies in the Twenty-First Century Methods of Information in Medicine Nov, 37(4-5):
THE Review of ideal characteristics of a controlled medical vocabulary / nomenclature.
Perhaps the best READING review of medical vocabulary / nomenclature available.

6. Content, content, content
First criticism of ANY nomenclature (by users) is lack of content
At least 3 approaches:
Enumerate all possible concepts (both simple and complex)
Provide all necessary “atoms”; create effective syntax; “teach” the syntax to users (or systems); hope for the best.
Drastically limit the scope of the nomenclature.
Restricting a nomenclature may actually improve usability of the nomenclature for a limited purpose, however:
It restricts expressivity
The next project and the next interaction require development of a new nomenclature
Connections between projects require “mapping”.
Users will not be happy.
Might be easier to build and use a large single nomenclature.

7. Concept Orientation Concept – an embodiment of a particular meaning
Characteristics:
Non-vagueness - Concepts must correspond to at least one meaning
Non-ambiguity - Concepts must correspond to no more than one meaning
Non-redundancy - Meanings correspond to no more than one concept

8. Concept permanence
Once created, the meaning of a concept is inviolable.
Any “meaningful” change requires retirement and reassignment of ID.
Concept identifiers can NEVER be reused.
Used to provide the history of concept status.
Contributes to stability of legacy information.

9. Non-semantic identifier
Unique name
Using the name as identifier inhibits (prohibits?) improvements in a concept’s “name”
Harder to cope with synonymy.
Hierarchical designators (codes with meaning) inhibit classification
Monohierarchies provide inadequate classification capability for retrieval purposes.
Polyhierarchies cannot be supported.
(A concept can’t be in its multiple logical locations).

10. Polyhierarchies Medical concepts are often classified in multiple ways
By site
By pathology
By function
Etc…
E.g. Acute bacterial pneumonia
It is a bacterial (infectious) disease
It is a pulmonary disease
It is an inflammatory condition
It is an acute condition

11. Formal definitions
A collection of relationships to other concepts in the vocabulary
Acute Bacterial pneumonia
Causative agent = bacteria
Has location = lung
Has morphology = inflammation
Has course = acute

12. Evolve Gracefully
A nomenclature must have a strategy for coping with new content.
The bane of home grown nomenclatures
Who’s looking after your list of concepts?
Nomenclature maintenance is not everyone’s cup of tea.
A controlled nomenclature serves as an “arbiter” of sorts.
A nomenclature used by more than one organization (PH lab) must have update and distribution mechanisms in place.

13. Recognize redundancy Redundancy must be avoided in the concept list
Redundancy must be provided for using a synonym mechanism.
Personal preference and dispersed training insures that there exist multiple ways to say almost anything.
They’re still talkin’ about the same thing.

14. SNOMED CT Top-level Hierarchies
Body structure
Clinical finding
Environment or geographical location
Event
Linkage concept
Observable entity
Organism
Pharmaceutical / biologic product
Physical force
Physical object
Procedure
Qualifier value
Record artifact
Situation with explicit context
SNOMED CT Model Component
Social context
Special concept
Specimen
Staging and scales
Substance

15. Complaints about SNOMED CT
It’s too…
Big
Complicated
Expensive
Yes but…
We can make it smaller (sort of), and use smaller pieces (for most purposes).
We can use it in simple and straightforward ways
Yeah, while the terminology is free, it’s a bit expensive to make it work.

16. Is the effort/expense worth it?
IF the long-range goal is useful…
The selected standards adhere to design specifications that have developed through hard experience in the medical profession.
Essential / desirable features have been documented.
The selected standards represent extraordinary functionality, produced and maintained at great cost to the medical profession.

17. Reportable condition reporting
Demographics - Race and ethnicity
Occupation and social context concepts
List of reportable diseases
Lab tests that support disease lists
Result values for non-numeric tests
Place to put the concepts in the message structures
Lab to Lab
Lab to network

18. Subsets of standards P.H. Reportable P.H. disorders SNOMED-CT, HL-7,
LOINC
P.H. Reportable
General practice
Specialty practice
P.H. disorders

19. SNOMED Data Structure

20. SNOMED Core Concepts Table Descriptions Table Relationships Table
Each row in this table represents a concept relevant to the health domain.
Descriptions Table
Each row in this table specifies a term that can be applied to describe a single clinical concept.
Relationships Table
Each row in this table specifies a relationship between two clinical concepts. The nature of each relationship is represented using a special kind of clinical concept.

21. Terminology of Terminology
Concept
embodiment of a particular meaning
Really a “virtual” element in the system
The string in the concepts table is a member of the related list of descriptions (for RF1).
Description
Any string used to represent a concept
Relationship
(in SNOMED) an object – attribute – value triple connecting two concepts through an attribute
Relationships in SNOMED are “stated” (explicitly modeled) or “inferred” (based on a classifier)

22. Concepts -> Descriptions
D2-0007F
Pneumonia (disorder)
Pneumonia (disorder) 3
Pneumonia 1
xxxxxx01x
Synonym in International Release 2
xxxx x
Synonym in US Extension 2
xxxyyyyyyy11x
Synonym In Local Extension 2
1 = “preferred” description (term) – preferred by SNOMED, perhaps not your users
2 = synonym (alternate)
3 = fully specified name

23. Concept -> Relationship
Fracture (morphologic abnormality)
M-12000
Associated Morphology (attribute)
G-C504
Fracture of Femur (disorder)
DD-13100
Concept Name
SNOMED ID
SCT ID
Concepts Table
Concept ID
Relationship ID
Relationship Table

24. SNOMED CT Component ID
The ComponentID data type is a 64-bit integer, which is subject to the following constraints:
Only positive integer values are permitted.
The minimum permitted value is 100,000 (6 digits)
The maximum permitted value is 999,999,999,999,999,999 (18-digits).
As result of rules for the partition-identifier and check-digit, many integers within this range are not valid SCTIDs.

25. SNOMED CT Component ID
The ComponentID does not contain semantic information related to the meaning of a concept or term
It does have a structure that is designed to allow different types of terminological components to be recognized.
The nature of a component can be derived from the table in which a component is distributed.
Partitioning the ID avoids reuse of the same identifier for a different type of component – thus avoiding both ambiguity and duplication.
This also allows the nature of the identifier to be recognized when stored in a record or transferred in a message.

26. SNOMED CT ComponentID format
SCTID for International release component.

27. SNOMED CT Extension ID Format
SCTID for a component in an extension.

28. A Word about SNOMED IDs (legacy codes)
Currently still assigned by IHTSDO for each release
Do NOT support differentiation among description types
Are discouraged/deprecated by IHTSDO
May not be “legally” assigned by SNOMED extension managers
Thus no way to link extension terms to core using legacy codes
Will be eliminated in the future

29. SNOMED CT Release Format 2 (RF2)
Addresses shortcomings of RF1
Provides a comprehensive history mechanism of all components
New attribute for “ownership” (moduleID)
Extended mechanism for creation of Reference Sets (refsets)
Supercedes subsetting mechanism if RF1
Replaces all status codes with components (everything is a component)
First production release July 2011
RF2 → RF1 conversion tool available

30. Accessing SNOMED Documentation
User’s Guide
A terminology user’s intro to SNOMED CT
Editorial Guide
Describes how to model SNOMED CT content
For content developers
Technical Implementation Guide
Aimed at technical implementers (developers)
Updates on the web version are ongoing

31. Additional introductory material
CAP STS offers free Introductory webinars
Introductory you tube videos by Dr. Kent Spackman, IHTSDO Chief terminologist

32. SNOMED CT Post-coordination
What is post-coordination?
Create a new concept by adding specificity to an existing SNOMED concept.
Discussion for another time

33. SNOMED Extensions
Enable authorized organizations to add Concepts, Descriptions, Relationships and Subsets to complement those that are centrally maintained as the International release content of SNOMED CT.
specialized terminology needs of an organization.
Extensions maintain unique identification across organizations for data transmission and sharing.

34. 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.

35. NLM’s Role Relating to Interoperability
Central coordinating body for clinical terminology standards within the U.S. Department of Health and Human Services
Coordinate efforts with the Office of the National Coordinator for Health Information Technology (ONC)
Distributor (within the UMLS) of:
HIPAA classifications & code sets AND
Terminologies required for EHR certification
Support for development and maintenance of standard terminologies

36. NLM’s Relationship to IHTSDO
Charter member on behalf of US/HHS
US distributor of SNOMED CT (via UMLS)
US licensor of IHTSDO Affiliates (via UMLS)
Serve on IHTSDO:
General Assembly (US Representative and Chair)
Member Forum (US Representatives and Vice-Chair)

37. UMLS Terminology Services (UTS)
Access to UMLS domain objects
Web site to browse, search, display, download
Metathesaurus and SNOMED CT browser
Authenticated, secure access to data requiring a UMLS license
One-stop access to terminology resources and applications at the NLM
Web services for programmatic access

39. SNOMED CT Resources

40. SNOMED CT at NLM

41. SNOMED CT International Release

42. SNOMED CT Browsers
15 Active browsers listed

43. NLM SNOMED CT/UMLS Browser

44. NLM SNOMED CT/UMLS Browser Why yet another SCT browser?
Leverages the UMLS to find SCT concepts
Allows location of SNOMED CT concepts using UMLS descriptions
As part of UTS, will link directly to other UTS services

45. Restrict to a specific top level concept
Can limit to active concepts only
Full information about concept available
Results pared down with additional search terms

46. No SNOMED CT Description?
Informs you whether there is a UMLS concept matching your search term

47. Concept exists in ICD9; ICD10CM and MEDCIN
UMLS Concept
Concept exists in ICD9; ICD10CM and MEDCIN

48. US Extension to SNOMED CT

49. U.S. Extension of SNOMED CT
NLM-maintained SNOMED CT components for U.S. use cases
Concepts jurisdictionally or domain specific
Rapid access to identifiers for implementers
Interim concept IDs pending IHTSDO approval
Regulatory or legislatively mandated terms
Domains out of scope for international release
Specific inclusion and exclusion criteria

50. US Extension of SNOMED CT…
Identifiers in NLM namespace:
First release in March 2011
Latest release scheduled for March 1, 2012
Harmonized with the latest International release
Future releases approx. one month after International release
Future releases may come more frequently

51. NLM SNOMED CT Content Request Submission (USCRS)

52. Rationale for USCRS
IHTSDO requires submissions to the International release to go through the member National Release Center
Existing request system being phased out
No new accounts accepted
Older users “grandfathered – in”
Needed support for U.S. users who need to add content to SNOMEDCT
Support users who need content with stable (maintained) identifiers before next release
Must support functions defined by IHTSDO
Triage and handling by NLM

53. USCRS Login
Uses UTS Login

54. Main Screen

55. New request allows a number of request types
Search allows you to search all current requests from any user

56. Dentistry
123445
Supernumerary second incisor of maxilla (disorder)
Supernumerary second incisor of maxilla
Teeth which appear in addition to the regular number of teeth.
Needed to support dental findings

57. Currently “Post-beta” General availability Fall 2011 Future phases
USCRS Status
Currently “Post-beta”
General availability Fall 2011
Future phases
Access to complete history of request changes
Manager alerts (priority todo)
Notes enhancements: links & attachments
Enhanced reporting capabilities (e.g. report of submitter activity)
Duplicate request identification and review
Extended request types – ref sets, content areas, etc.
Mobile app interface

58. State diagram for requests

59. Questions? Jim Case casejt@mail.nih.gov