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SNOMED Clinical Terms (Snomed CT) – the language for healthcare A presentation for the SNOMED Clinical Terms (Snomed CT) – the language for healthcare A presentation for the KIDDM Mashup, 17 th September 2007 Ian Herbert Vice Chair BCS Health Informatics Forum With grateful acknowledgements to Dr David Gain of NHS CFH

Why do we need Snomed-CT? To enable consistent representation & retrieval of clinical info: Why do we need Snomed-CT? To enable consistent representation & retrieval of clinical info: • about individual patients • in knowledge sources, e. g. drug formularies & guidelines To avoid a combinatorial explosion of the terms needed To provide a flexible set of classifications of terms Need a terminology that can be extended quickly & indefinitely This necessary (but may not be sufficient) for: • analysing patient information, e. g. for mgmnt & research • automated decision support, e. g. for safe prescribing • semantic interoperability between care providers & systems □

What is SNOMED CT? A conceptual classification A controlled clinical vocabulary h Healt on What is SNOMED CT? A conceptual classification A controlled clinical vocabulary h Healt on Lexic Dictionary of Clinical Concepts Thes a of Te urus rms SNOMED CT is a terminological resource that can be implemented in software applications to represent clinically relevant information reliably and reproducibly □

Why not use ICD 10 or OPCS 4? Not not rich enough (or intended) Why not use ICD 10 or OPCS 4? Not not rich enough (or intended) for patient records No facility to combine expressions to clarify meaning • ‘emergency’ + ‘thoracotomy’ • ‘recurrent’ + ‘IGTN’ + ‘left’ + ‘great toenail’ Updates too slow (every 10 years for ICD) SNOMED CT can respond reasonably quickly to • changes in the wider field of medicine • changes in local policy • individual requests for additions and will never be complete □

What’s wrong with free text? Free text is an extremely valuable and flexible way What’s wrong with free text? Free text is an extremely valuable and flexible way of recording details about individual circumstances, but… • The meaning may be ambiguous, & open to misinterpretation • Its meaning is not available for computation, e. g. • it can’t automatically be analysed for audit or payment • it can’t direct care pathways • it can’t trigger automatic warnings about allergic reactions or interactions □

How is the information used? Decision support Clinical audit Documentation in electronic records Reporting How is the information used? Decision support Clinical audit Documentation in electronic records Reporting Direct care Administrative / management information Epidemiology Research Summaries Billing & reimbursement Indirect Care Aggregation functionality Resource management

One concept, many names Some of the descriptions associated with Concept. ID 22298006: • One concept, many names Some of the descriptions associated with Concept. ID 22298006: • Fully Specified Name: Myocardial infarction (disorder) Description. ID 751689013 • Preferred term: Myocardial infarction Description. ID 37436014 • Synonym: Cardiac infarction Description. ID 37442013 • Synonym: Heart attack Description. ID 37443015 • Synonym: Infarction of heart Description. ID 37441018

Avoiding ambiguity To a neurologist Cord compression means Spinal cord compression To a midwife Avoiding ambiguity To a neurologist Cord compression means Spinal cord compression To a midwife Cord compression means Umbilical cord compression Transmission and sharing of information requires consistency of terminology – and its use □

Will the computer limit what I can say? More concepts • 400, 000 health Will the computer limit what I can say? More concepts • 400, 000 health care concepts More descriptions • 1, 000 clinical terms More information • 1, 500, 000 semantic relationships Contextual modification of expressions • possible, Family history of, planned, refused, aborted etc. □

Depth of clinical expression peripheral angiography special peripheral angiography procedures peripheral graft arteriogram femoral-femoral Depth of clinical expression peripheral angiography special peripheral angiography procedures peripheral graft arteriogram femoral-femoral crossover arteriogram □

How is it organised? Multiple top level concepts, e. g: - body structure Each How is it organised? Multiple top level concepts, e. g: - body structure Each with a hierarchy of concepts beneath Strictly organised by ‘IS A’ relationships - index finger ‘is a kind of’ finger - finger ‘is a kind of’ hand part, etc Each concept may have permitted qualifiers, e. g. - pain ‘has qualifier’ severity □

Hierarchies Examples Clinical Finding: Contains the sub-hierarchies of Finding and Disease Important for documenting 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/intervention: 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 Lingual thyroid ( body structure) Neoplasm (morphologic abnormality)

Hierarchies Examples Organism Coverage includes animals, fungi, bacteria and plants Necessary for public health 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 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 mechanisms of injury Fire Gravity Pressure change

How is it constructed? Defining and qualifying characteristics used to construct & refine a How is it constructed? Defining and qualifying characteristics used to construct & refine a terminological model of healthcare Concepts combined with Attribute-Value pairs • Procedure with: - method – excision - site – both tonsils - using – laser device (the post-coordinated representation) = Bilateral laser tonsillectomy (the pre-coordinated equivalent & a ‘kind of’ tonsillectomy) ‘Method’, ‘site’ & ‘using’ are defining characteristics An additional ‘success’ attribute would be a qualifier □

Getting the right Snomed CT term • • Search for term if you think Getting the right Snomed CT term • • Search for term if you think it’s in there Search the term hierarchies to find the term Use a combination of the two Info. can always be entered in post-coordinated form, q. v. the bilateral laser tonsillectomy example, but equivalent pre -coordinated term may be available • Where system constrains context, a data entry template can have possible terms in manageable drop-down lists (including post-coordination qualifiers) • Automatic encoding of entered text • highly desirable, but far from reliable at present • generated codes must be approved by user before commital □

Snomed-specific issues • Detecting equivalence of same thing said in pre-coordinated & various post-coordinated Snomed-specific issues • Detecting equivalence of same thing said in pre-coordinated & various post-coordinated representations • Expressing negation - this comes in many forms, e. g: • diabetes excluded • appendectomy not done • no pain in right leg • NAD - nothing abnormal detected • Consistent authoring of the terminology • Enabling accurate speedy use in unconstrained situations, e. g. when taking a patient history □

- & non-Snomed-CT specific issues • Human beings are lazy & good at inference - & non-Snomed-CT specific issues • Human beings are lazy & good at inference • So patient records full of short cuts, e. g: • BP 140/80 means ‘blood pressure taken and systolic pressure observed to be 140 mm hg, and diastolic pressure 80 mm hg’. Assumed to be of patient whose record it’s in, & taken during the encounter it lies within • Computers are pedantic & pernickety. So is Snomed. It has xx codes for a blood pressure • Users want biggest bang per keystroke buck, so unconstrained searching for terms & post-coordination not popular □

Why is Snomed CT ‘not sufficient’? • • Snomed CT consists of concepts, i. Why is Snomed CT ‘not sufficient’? • • Snomed CT consists of concepts, i. e. types Doesn’t deal with numeric values, e. g. weight 70 kg Doesn’t identify individual objects, e. g. people So needs to be used within an external syntax to bind instances of Snomed concepts to their context, e. g. : • • who it’s about - the subject (typically a patient) when action / event occurred or observation made who performed action / made observation where action / event occurred or observation made □

Where are we now? • • • Snomed CT adopted by the NHS Now Where are we now? • • • Snomed CT adopted by the NHS Now in the hands of an independent international body Adopted by several countries, more coming Has no significant global rivals But not much practical experience in patient record keeping with it yet, virtually none in real-time □

Are we winning? “We will know we have succeeded when clinical terminologies in software Are we winning? “We will know we have succeeded when clinical terminologies in software used and re-used, and when multiple independently developed medical records, decision support, and clinical information retrieval systems sharing the same information using the same terminology are in routine use. ” Alan Rector 2000 “Clinical Terminology: Why is it so hard? ”