LOINC and SNOMED - HL7 E Learning Course
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LOINC AND SNOMED
Tim Benson
Abies Ltd
Wellcome Trust Sintero Server Project
Cardiff University
Author:
Principles of Health Interoperability HL7 and SNOMED, Springer 2010
OUTLINE
Origins of LOINC
Origins of SNOMED CT
Complementary or Competitive
SCOPE OF LOINC
Clinical Laboratory Tests
The test not the result
Clinical observables
“Eye colour”, not “Blue eyes”
Form headings
Document types
Assessment scales
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 V2.0 1988
OBX Segment
EU EUCLIDES and OpenLabs projects
HL7 V2 OBX SEGMENT
Turn-round document
Observable
Code
Value
Code
Physical quantity
EUCLIDES
European Clinical Laboratory Data Exchange
Standard 1988-1991
Georges De Moor, Gent
6 dimensional classification
LOINC CODES
LOINC Code
Consecutive number + Check digit
e.g. 12345-9
Short convenient name
Long common name
All codes are pre-coordinated to common concept
model
Six dimensions
slightly different from EUCLIDES
LOINC DIMENSIONS
Component
Property
sample or body part
Scale
point in time or period
System
kind of property measured
Timing
what is being measured
nominal, ordinal, interval or ratio
Method
procedure used to produce the result or other
observation
RELMA
Regenstrief LOINC Mapping Assistant
LOINC database search
Map local codes to LOINC codes
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
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
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
ORIGINS OF SNOMED CT (2)
Read Codes
Coded terms in EHR
e.g. “Blue Eyes”
Developed by Abies and James Read for use in GP
computer system 1983-1986
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
READ CODE (V1,2) CHAPTERS
Diagnoses
Medication
BNF Chapters a-z
History and physical
ICD Chapters A-Z
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)
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
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
BENEFITS OF SNOMED CT
Future-proof structure
Inherently multi-lingual
Broad coverage
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)
EDUCATION – NEEDS A BLENDED
APPROACH
1.
2.
3.
4.
5.
Learn by doing (assignments and examples)
Face-to-face presentations
Web-based presentations and videos
User guides and books
Pick it up from colleagues
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)
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
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
CONCLUSIONS
LOINC and SNOMED CT were originally
designed to do different things
They are complementary