Introduction to SNOMED CT

Jo OakesTraining Consultant

NHS Data Standards & Products

Agenda

• History of Coding• What is SNOMED CT?• What are the benefits of SNOMED CT?

History of Coding

A Background to Coding

17th CenturyJohn Gaunt’s Weekly Bills of Mortality

London Bills of Mortalityevery Thursday from 1603 until the 1830s

Aggregated Statistics 1665

Manchester MercuryJanuary 1st 1754

Executed 18Found Dead 34Frighted 2Kill'd by falls and other accidents 55Kill'd themselves 36Murdered 3Overlaid 40Poisoned 1Scalded 5Smothered 1Stabbed 1Starved 7Suffocated 5

Aged 1456Consumption 3915 Convulsion 5977Dropsy 794Fevers 2292 Smallpox 774Teeth 961Bit by mad dogs 3Broken Limbs 5Bruised 5Burnt 9Drowned 86Excessive Drinking 15

List of diseases & casualties this year

19276 burials

15444 christenings

Deaths by centile

Quotation“I am fain to sum up with an urgent appeal for adopting … some uniform system of publishing the statistical records of hospitals. There is a growing conviction that in all hospitals, even in those which are best conducted, there is a great and unnecessary waste of life … In attempting to arrive at the truth, I have applied everywhere for information, but in scarcely an instance have I been able to obtain hospital records fit for any purposes of comparison … If wisely used, these improved statistics would tell us more of the relative value of particular operations and modes of treatment than we have means of ascertaining at present.”

Florence Nightingale

Notes on Hospitals, London: Longman, Green, Roberts, Longman and Green, 1863.

Florence Nightingale 1856

Outcome groups

Relieved

Not Relieved

Died

Dr William Farr 1855

Developed the ‘International Listing of Causes of Death’

Adopted by World Health Organisation (WHO) in 1948

History of the Clinical Terms

1985 4 byte set introduced1990 Version 2 introduced1990 Purchase by Department of Health1992 Terms Projects1994 Version 3 introduced1999 SNOMED Collaboration2007 IHTSDO created

What is SNOMED CT?

First things first…

• Systematized Nomenclature of Medicine • SNOMED CT- Clinical Terms• Developed by NHS and the College of American

Pathologists (CAP)• Merges the content of the NHS’s Clinical Terms

Version 3 (The Read Codes) with CAP’s SNOMED Reference Terminology (SNOMED RT®)

• For the front end users (clinicians)• SNOMED is not about the codes, but the terms – it is

unlikely clinicians will see the codes

SNOMED CT overview

Comprehensive clinical terminology that is used to:• Code• Retrieve, and • Analyze clinical data

Comprises of:• Concepts• Terms• Relationships

All necessary to precisely represent clinical information across the scope of health care.

Basic Elements of SNOMED CT

Concepts• The basic units of SNOMED CT

Descriptions• These relate terms that name the concepts to the

concepts themselves. Each concept has at least two Descriptions.

Hierarchies• Concepts are organized into twenty SNOMED CT

hierarchies (in UK extension). Each hierarchy has sub-hierarchies within it.

Relationships• Relationships are the connections between concepts

in SNOMED CT.

Concepts

• Represent distinct clinical meanings• Identified by a unique numeric identifier (Concept ID) that

never changes and a unique human readable name (Fully Specified Name)

• Associated with each concept is a set of relationships (the “logical definition”) and a set of names or terms

• Differing levels of granularity• There are currently around 400,000 terms in SNOMED CT

Descriptions

• Concept descriptions relate the terms or names of a SNOMED CT concept to the concept itself.

• “Term” in this context means a phrase used to name a concept. A single description associates a single term with a single Concept ID.

• Each of these descriptions has a unique Description ID, but all of these descriptions are associated with a single concept (and a single Concept ID).

• Descriptions are an important interface property because they give end users the flexibility to use terms that they are familiar with.

• The Concept ID ties terms with the same meaning together to aid consistent interpretation and retrieval.

Description types

Preferred Term• The most common word or phrase used by

clinicians to name a conceptThe Fully Specified Name

• Provides an unambiguous way to name a conceptSynonyms

• The rest of the names that may be used for a concept

Some of the descriptions associated with ConceptID 22298006:• Fully Specified Name: Myocardial infarction (disorder)DescriptionID 751689013

• Preferred term: Myocardial infarctionDescriptionID 37436014

• Synonym: Cardiac infarctionDescriptionID 37442013

• Synonym: Heart attackDescriptionID 37443015

• Synonym: Infarction of heartDescriptionID 37441018

Example of components

Words and semantics

It’s not what you say, it’s what you meanThe meanings of words and phrases change

• In context• Between places• Between disciplines and specialties• Between different times

SNOMED CT encodes meaning, not just words

The problem with words and meaning

What is a “pyogenic granuloma?” • Pyogenic = pus forming• Granuloma = a collection of inflammatory cells

of a particular typeBut

• Pyogenic granuloma = a benign tumor of small blood vessels of the skin

• It is neither pyogenic nor a granuloma.Combinations are frequently very different from the sum of their parts

The problem with words and meaning

Does “the leg” mean the same as “the lower limb”?• That’s what the average person assumes• Health professionals also often use the word “leg” in this way

But medical dictionaries take a different view• Stedman’s: “the segment of the inferior limb between the

knee and the ankle”• Dorland’s: “that section of the lower limb between the knee

and ankle”“Ordinary” dictionaries recognise both meanings

Some formal definitionsconflict with ordinary usage

Practical Tip

• Dressing (oneself)

• Dressing (e.g. a bandage)

• Dressing (assisting the person to dress)

• Dressing (of wound)

• Dressing (observable entity) parent – personal care activity

• Dressing, device (physical object)

• Dressing patient (procedure)

• Dressing of wound (procedure)

SNOMED is not the “language police”

SNOMED CT seeks to • Establish how language is used by clinicians• To represent meaning as faithfully as possible.

SNOMED CT declares what it thinks a phrase means • To reflect current usage • To minimise ambiguity• Not to shape or control the way a phrase is used

If you want someone to demand that clinicians change what they call “pyogenic granuloma” • That may be someone else’s job • It’s not something SNOMED CT is trying to do

Top-level hierarchies (October 2007)

1. Clinical finding 2. Procedure

3. Observable entity 4. Body structure

5. Organism 6. Substance

7. Pharmaceutical/biologic product 8. Specimen

9. Physical object 10. Physical force

11. Events 12. Environment or geographical Location

13. Social context 14. Situation with explicit context

15. Staging and scales 16. Qualifier value

17. Special concept 18. Linkage concept

19. Record artifact 20. SNOMED-CT UK Administrative Concepts

Hierarchies Examples

Clinical Finding: Contains the sub-hierarchies of Finding and

Disease    Important for documenting clinical disorders and

examination findings

Finding: Swelling of arm Disease: Pneumonia

Procedure: Concepts that represent the purposeful activities

performed in the provision of health care

Biopsy of lung Diagnostic endoscopy Foetal manipulation

Observable entity Concepts represent a question or procedure which,

when combined with a result, constitute a finding

Gender Tumour size Ability to balance

Body structure Concepts include both normal and abnormal

anatomical structures Abnormal structures are represented in a sub-

hierarchy as morphologic abnormalities

Entire Liver ( body structure) Neoplasm (morphologic abnormality)

Hierarchies Examples

Organism Coverage includes animals, fungi, bacteria and

plants necessary for public health reporting and used in evidence-based infectious disease protocols

Hepatitis C virus Streptococcus pyogenes Acer rubrum (Red maple) Felis silvestris (Cat)

Substance Covers a wide range of biological and chemical

substances Includes foods, nutrients, allergens and materials Used to record the active chemical constituents of

all drug products

Dust Oestrogen Haemoglobin antibody Methane Codeine phosphate

Pharmaceutical/Biological Product This hierarchy is separate from the Substance

hierarchy in order to clearly distinguish drug products (products) from the chemical constituents (substances) of drug products

Sex hormone product (product)Mineralocorticoid preparation (product)beta-Blocking agent (product)

Hierarchies Examples

Specimen Contains concepts representing entities that are

obtained for examination or analysis, usually from a patient

They are defined in terms of the normal or abnormal body structure from which they are obtained, the procedure used to collect the specimen, the source from which it was collected, and the substance of which it is comprised

Nail specimenPus specimenClean catch urineSpecimen from patientCalculus specimen

Physical object Concepts include natural and man-made objects Focus on concepts required for medical injuries

Prosthesis Artificial organs Vena cava filter Colostomy bag

Physical force Includes motion, friction, electricity, sound,

radiation, thermal forces and air pressure Other categories are directed at categorizing

mechanisms of injury

Fire Gravity Pressure change

Hierarchies Examples

Events Concepts represent occurrences that

result in injury Exclude all procedures and interventions

Flash flood Motor vehicle accident

Environment or geographical location Includes all types of environments as

well as named locations such as countries, states, and regions

Islands of North America NHS day treatment facility Cancer hospital

Social context Contains social conditions and

circumstances significant to healthcare Includes family and economic status,

ethnic and religious heritage, and life style and occupations

Economic status (social concept) Asian (ethnic group) Clerical supervisor (occupation) Donor (person) Thief (life style) Judaism (religion/philosophy)

Hierarchies Examples

Situation with Explicit Context To represent medical information

completely, it is sometimes necessary to attach additional information to a given concept

If this information changes the concept's meaning, it is known as context

This category represents concepts that carry context embedded within in them

No family history of stroke Nasal discharge present Aspiration pneumonia resulting from a procedure

Staging and scales Contains concepts naming assessment

scales and tumour staging systems

Glasgow coma scale (assessment scale) Alcohol use inventory (assessment scale) Dukes staging system (tumour staging)

Hierarchies Examples

Qualifier Value Contains values for SNOMED CT

attributes Values that are not contained elsewhere

in SNOMED CT are needed for attributes and these are contained here

BilateralOpenReducedRemoval – actionRight

Special Concept This has three sub hierarchies containing

concepts which have been set aside from the logical hierarchy of semantic subtypes

Inactive concept – the supertype ancestor of all Inactive ConceptsNavigation concept – the supertype of all Navigation ConceptsNamespace concept – the supertype of all Namespace Concepts

Hierarchies Examples

Linkage Concept • Attributes and other concepts used to link

concepts with other concepts

Laterality, Method, Severity, Is manifestation of, Has reason

Record Artefact• Reports and forms associated with the

delivery of healthcare

Jury exemption form, Post-mortem report

SNOMED CT UK Administrative Concept Concepts that are unique to the

administrative processes in healthcare in the UK

Seat belt exemption admin, Item of service administration

Relationships

The connections between concepts• Every SNOMED CT concept has at least one

relationship to another concept• Relationships characterize concepts and give them

their meaning• The list of relationships for a particular concept makes

up the logical definition of that concept2 types:

• IS-A (sub-type/super-type)• Attribute

Relationships cont…

• ‘Is a’ relationship also known as supertype-subtype or parent child relationships

• A relationship is assigned only when that relationship is always known to be true

IS-A relationships

SNOMED CT’s hierarchies consist entirely of IS-A relationshipsIS-A relationships in the Inflammatory disorder hierarchy:

• Lumbar discitis IS-A Discitis• Discitis IS-A Arthritis• Arthritis IS-A Inflammatory disorder• Inflammatory disorder IS-A Disease

Some concepts have more than one IS-A relationship. These concepts have parent concepts in more than one hierarchy:

• Lumbar discitis IS-A Discitis• Lumbar discitis IS-A Disorder of back

Excisional biopsy of lymph node

Surgical biopsy of lymph node

Biopsy oflymph node

Procedure on lymph node

Procedure

IS_A

IS_A

IS_A

IS_A

Bacterial pneumonia

Infective pneumonia

Pneumonia

Disease of lung

Disease of respiratory system

Disease

SNOMED CT Concept

Bacterial infectious disease

Infectious disease

Attribute Relationships

• Characterize and specify concepts• An example of an attribute is FINDING-SITE,

which is used to further specify Disease concepts

e.g. part of the logical definition of the concept Pneumonia in SNOMED CT is:

Concept = Pneumonia Attribute = FINDING-SITE Value of attribute = Lung structure

Attribute RelationshipsAttribute Relationships

pain in limbfinding lower limb

pain in lower limb

pain in calf

lower limbstructure

structure of calf of leg

Why is SNOMED CT relevant?Why is SNOMED CT relevant?

Cross Boundary

Universal Language

The Spine

SNOMED CT Delivers Information

Most clinicians should neither know nor care

- How many digits are in a concept identifier- How many concepts are in SNOMED CT- How descriptions and relationships are tied to

concepts

David Markwell, Chair of SNOMED Concept Model Working Group

What clinicians care about is

• Clinical records they use meet their needs• Record system components that work together

reliably• Being able to easily express the information they

wish to enter in a patient record• Being able to retrieve information to support

delivery of care or for secondary uses with a minimum of extra effort

David Markwell, Chair of SNOMED Concept Model Working Group

What are the benefits of SNOMED CT?

SNOMED CT: The Benefits

The benefit of recording information in a standard terminology such as SNOMED CT is linked to the benefits of the electronic care record and the benefits of recording clinical information in a structured form

Benefits of an Electronic Record

• Reduced storage costs• Can be accessed from many places• Can be transferred quickly• It is legible

Benefits of a Structured Record

• Can display logical progression of clinical data• Can retrieve clinical data based on situation or

author• Allows clinical data items to be transmitted

longitudinally through a patient’s record

Benefits of using a Clinical Terminology

• Controlled vocabulary

Point of care uses:-• The ability to search records for clinical

information• Identification of patients who match a given set of

criteria• Provision of decision support

Benefits of using a Clinical Terminology

Aggregation uses:-• Public health monitoring• Outcomes analysis• Performance analysis

Benefits of using SNOMED CT

• Provides a consistent terminology across all care domains

• SNOMED CT allows precise recording of clinical information

• SNOMED CT has an inherent structure• SNOMED CT is a developing international

standard

What does it mean for clinicians?

• It will be legible!• May encourage more detailed documentation• Decrease duplication of recording patient

information• Less ambiguous/better clarity of clinical

information• More communicable• Consistency leads to better sharing of information• Improved granularity for research purposes

The Future for Clinical Coders

What does this mean for Clinical Coders?

• The current system of ICD-10 and OPCS-4 classification is not going to disappear overnight

• The cross-mapping of SNOMED CT to ICD-10 or OPCS-4 can only ever be a semi automatic process

• Coders will continue to be responsible for the clinical classification coding and trust payment

• Coders will be supported by new tools that help with some of the simpler translations of SNOMED CT to ICD-10 and OPCS-4

What does this mean for Clinical Coders? (2)

• NHS CFH Informatics and the NHS Classifications Services are assessing the training and support coders require under the Education, Training and Development unit with CFH

• Support for clinical uses of SNOMED CT and maintenance of SNOMED CT subsets is potentially an enormous opportunity for people who understand the issues surrounding coded medical information and are skilled at performing complex data analysis

• If the process of populating HRGs from SNOMED CT can be proved, there will be additional benefits in rationalising the many coding schemes currently used in medicine.

Is SNOMED CT Perfect?Is SNOMED CT Perfect?

“The man who makes no mistakes does not usually make anything.”

• E J Phelps (1822 - 1900)

… so SNOMED CT is not “perfect”

The goal is fitness for purpose not perfection

Contact details and further Contact details and further informationinformationNHS Data Standards & Productshttp://www.connectingforhealth.nhs.uk/standards/

- SNOMED CThttp://www.connectingforhealth.nhs.uk/snomed

- UK Terminology Centre (UKTC)http://www.ihtsdo.org.uk

- HelpdeskDS&P Helpdesk :

• Tel : 0044 (0)1392 206 248• Email: datastandards@nhs.net