1. LOINC and SNOMED Tim Benson Abies Ltd
Wellcome Trust Sintero Server Project
Cardiff University
Author:
Principles of Health Interoperability HL7 and SNOMED, Springer 2010

2. Outline Origins of LOINC Origins of SNOMED CT
Complementary or Competitive

3. Scope of LOINC Clinical Laboratory Tests Clinical observables
The test not the result
Clinical observables
“Eye colour”, not “Blue eyes”
Form headings
Document types
Assessment scales

4. Origins of LOINC Logical Observation Identifiers Names and Codes
Designed for use in interoperability
Clem McDonald
ASTM 1238:88 Standard Specification for Transferring Clinical Laboratory Data Between Independent Computer Systems
HL7 V
OBX Segment
EU EUCLIDES and OpenLabs projects

5. HL7 v2 OBX segment Turn-round document Observable Value Code
Physical quantity

6. EUCLIDES European Clinical Laboratory Data Exchange Standard 1988-1991
Georges De Moor, Gent
6 dimensional classification

7. LOINC Codes LOINC Code Short convenient name Long common name
Consecutive number + Check digit
e.g
Short convenient name
Long common name
All codes are pre-coordinated to common concept model
Six dimensions
slightly different from EUCLIDES

8. LOINC Dimensions Component Property Timing System Scale Method
what is being measured
Property
kind of property measured
Timing
point in time or period
System
sample or body part
Scale
nominal, ordinal, interval or ratio
Method
procedure used to produce the result or other observation

9. RELMA Regenstrief LOINC Mapping Assistant LOINC database search
Map local codes to LOINC codes

10. Problems of LOINC Complex
Many similar codes with only small differences
mass concentration v molecular concentration
anatomical position of pulse or BP
Dimensions are not hierarchical so limits subsumption testing

11. Good aspects of LOINC Completely free
Does what it claims to do (but no more)
Fit for purpose
Easy and quick to add new codes

12. Origins of SNOMED CT (1) SNOMED CAP committee 1955 SNOP 1965
topography
morphology
etiology
function (physiology)
SNOMED 1975
SNOMED III 1993
SNOMED RT (Reference Terminology) 1997

13. Origins of SNOMED CT (2) Read Codes Used by all GPs in UK (100%)
Coded terms in EHR
e.g. “Blue Eyes”
Developed by Abies and James Read for use in GP computer system
Purchased by DH in 1990
V2 1990
Version 3 (CTV3) 1996
Used by all GPs in UK (100%)
Basis of payment
Unsuccessful in other specialties

14. Read Code (v1,2) Chapters Diagnoses Medication History and physical
ICD Chapters A-Z
Medication
BNF Chapters a-z
History and physical
Occupations (0), history and symptoms (1), physical examination findings (2)
Procedures
Diagnostic (3), lab (4), imaging (5), prevention (6), therapy (7), surgery (8), admin (9)

15. SNOMED CT Merger of Read Codes and SNOMED RT Reference Terminology
All concepts are in hierarchies (19)
Concepts
Descriptions (terms)
Relationships
Defining, qualifying, sub-type, association
Description Logic

16. Problems of SNOMED CT Much legacy baggage Lack of transparency
Lack of free access
Lack of good web-based tools
Complexity
Post-coordination is not yet a practical proposition
Undefined boundaries
Over-sold as answer to all terminology problems

17. Benefits of SNOMED CT Future-proof structure Inherently multi-lingual
Broad coverage

18. Education Problem Few people are competent in both LOINC and SNOMED
Clinical terminology is not taught well
One of 186 topics in AMIA Core Curriculum for Clinical Informatics (JAMIA, 2009)
Formal training is essential
93% of all those who rated themselves as competent had had more than 3 days formal training in SNOMED CT (Report for DH, unpublished)

19. Education – needs a blended approach
Learn by doing (assignments and examples)
Face-to-face presentations
Web-based presentations and videos
User guides and books
Pick it up from colleagues

20. LOINC and SNOMED CT together
Clinical statement consists of:
Narrative text
Context (who, when , where, etc)
Observable
Finding
(Rector A. What’s in a code, MEDINFO 2007)

21. Observable
“Observables” are qualities of patients that are present in all patients
and whose values or states are determined by observation
This is what LOINC is designed to code and does it well

22. Finding Information specific to a particular patient
Finding = Observable + Value
Value may be various data types
Physical quantity, code, date, text etc
SNOMED CT is good for Observation Value Codes

23. Conclusions
LOINC and SNOMED CT were originally designed to do different things
They are complementary