Disease Ontology: Where We Are

1. Kent A. Spackman, MD PhD Scientific Director, SNOMED Disease Ontology:Where We Are Workshop on Disease Ontology Baltimore, Maryland November 6, 2006

2. Where we are from a SNOMED perspective • The SNOMED terminology itself: • SNOMED contains 62,697 active “disorder” codes (and another 12,087 “limited status” codes related to ICD) • The terminology is freely available in the US, UK, Australia, and Denmark, and soon Canada, New Zealand, and other countries • It is designated as the terminology for diseases by several US federal agencies (NCVHS, CHI, FDA – drug product labels) • There is an open working group structure that invites your participation • Formation of a new international SDO with transfer of intellectual property from the CAP is expected to result in even more openness, particularly in research

3. Potential formation of new SDO CAP International Health Terminology SDO Own Manage & Support the NON- SNOMED CT portfolio SNOMED CT IP & IPR Supply a Support Service CAP Support Service SDO Managed Support Services Open Market Derivative Products New Technical Infrastructure Potential result of successful negotiation

4. Is SNOMED an ontology? • Depends on the definition of ontology • Prefer “controlled terminology” • Purpose: • Recording statements about individual patients in electronic records, to be used for patient care (including documentation and decision support), health care administrative purposes, and research • The content should be informed and shaped by formal ontological principles, but not limited only to the scope of a formal ontology

5. Defining “disease” is hard • No consensus definition exists • No clear path to achieving such a consensus is available to us • Medical community is fragmented and, frankly, not that interested • Probably best not to argue about the label, but instead define several (potentially overlapping) understandable, reproducible and useful categories

6. Codes, concepts and meanings • One meaning per code • Concepts themselves are in people’s heads. • And the things (entities) that the concepts reference via their meaning are in the real world. • In talking about the terminology, we sometimes are sloppy in saying “concept” when we mean “code” or “meaning of a code”

7. Meaning, not language • fundus • pyogenic granuloma • tumor • psoriasis • appendectomy • angiography • leg • anemia

8. URU criteria • Definitions should be Understandable by average clinicians, given brief explanations • We assess understandability by examining Reproducibility • We can ignore distinctions for which there is no Use in health care

9. What is a disease? • Multiple definitions given on the workshop web site, some emphasizing: • Abnormality • Dysfunction • Etiology • Adverse consequences / risk • Treatment

10. alcoholism obesity gambling addiction menopause jet lag unhappiness cellulite hangover anxiety about penis size penis envy pregnancy childbirth road rage ignorance low IQ bigotry loneliness ageing overwork boredom bags under eyes baldness wrinkles freckles big ears grey hair ugliness Are these diseases? In search of "non-disease“. BMJ 2002;324:883-885

11. BMJ 2002;324:883-885 ( 13 April ) • In search of "non-disease" • Richard Smith, editor. • The BMJ recently ran a vote on bmj.com to identify the "top 10 non-diseases." Some critics thought it an absurd exercise, but our primary aim was to illustrate the slipperiness of the notion of disease. We wanted to prompt a debate on what is and what is not a disease and draw attention to the increasing tendency to classify people's problems as diseases.

12. These don’t work as a definition • Anything coded by ICD • Any abnormal clinical finding • Any “disorder” • Anything fitting the field “diagnosis”

13. Diagnosis • Can be either a label or a process • What is a valid result of the process, or a valid target of the label, varies widely with context • NOT synonymous with disease

14. Diagnosis • The meaning of “diagnosis” is highly variable and depends on context • “Diagnosis as a label (which really is its common usage in clinical records) is a very different animal from the process. It is typically qualified by adjectival form such as "initial", "primary", "admission", "discharge", "differential", "working", "secondary", etc. According to the adjective it gains qualities which relate to administrative purposes (e.g. billing for "discharge diagnosis") or prompts a course of investigative action in others (e.g. "differential diagnosis" or "working diagnosis"). These uses have very different semantics from one another. They are not actions but are parts of the context surrounding the recording of a finding. … My view of this is that ‘diagnosis’ in all its flavours is an observation about another observation.” from an email by David Markwell on the HL7 vocab list.

15. What relationships define disease? • An early attempt: the “axes” of the Systematized Nomenclature of Pathology, 1965 • Topography • Morphology • Etiology • Function

16. Clinical finding attributesSNOMED CT, 2006 Acquired body structure, Anatomical concepts Finding site Associated morphology Morphologically abnormal structure Clinical finding, Substance, Physical object, Physical force, Events, Organisms, Pharmacological / Biological product, Procedure Associated with Clinical finding After Clinical finding, Procedure, event Due to Clinical finding, Event Organism, Substance, Physical object, Physical force Causative agent Has interpretation Findings values, Result comments Laboratory procedure, Observable entity, Patient evaluation procedure Interprets

17. Clinical finding attributes cont. First episode, New episode, Ongoing episode Episodicity Pathological process Pathological process Sudden, Gradual Onset Course Courses Clinical finding Has definitional manifestation Clinical finding Occurrence Periods of life Mild, Moderate, Severe Severity Procedure Finding method Performer of method, Subject of record Provider of history other than subject, Subject of record or other provider of history Finding informer

18. Diseases vs their manifestations • 1) Should we always distinguish a disease from its manifestation? • 2) is the manifestation also a disease? • Epilepsy, seizure. • Migraine headache disorder, migraine headache • Thrombotic disorder, thrombosis • Hypertensive disorder, hypertension • Anemia, low hemoglobin • Laceration of forearm • Fracture of navicular bone of wrist • Cataract • Cogwheel rigidity • Spastic gait

19. “Disorders” vs “observations” • Typically thought of as diseases and their manifestations • Observations are sometimes called findings, and sometimes findings are separated from symptoms and/or signs • Important to realize the word “finding” is used in SNOMED to mean things that can be observed or asserted to be present or absent, NOT assertions that they have in fact been observed or are present • CTV3 (1993-97) separated disorders from observations/findings • SNOMED RT (2000-2001) had merged them due to lack of reproducible criteria for separating them • SNOMED CT (2002- ) initially attempted to keep them separate, then gave up and merged them • We have been unable to come up with a reproducible clean distinction between findings and disorders

20. Findings & DisordersContinuants & Occurrents: Some Exploratory Ideas CMWG October 2006

21. Current advice • “Disorders are findings that are abnormal” • Difficult to get reproducibility • Consensus of what is abnormal and what is not • Strong sense that an abnormal finding is not necessarily a disorder • Words “finding” and “disorder” carry connotations that are different depending on the context or individual

22. Findings & Disorders • The finding/disorder distinction is not reproducible • We should probably think about a different set of distinctions within the “clinical findings” hierarchy that helps us decide • One code or two? • Same or different? • Examples: • anemia – low hemoglobin • Migraine (headache) disorder – migraine headache • Epilepsy – seizure

23. Some tentative categories: Occ) occurrents (things that happen: exposures, accidents, events) C0) continuants that may exist even when their defining characteristic(s) is/are not present (many disorders go here) C1) continuants whose defining characteristics must always exist, i.e. it is possible for them to be observed/detected (by some method)

24. Some test cases (1) Occ) occurrents (things that happen: exposures, accidents, events) C0) continuants that may exist even when their defining characteristic(s) is/are not present C1) continuants whose defining characteristics must always exist • bleeding • rash • pharyngitis • spasm

25. Some test cases (1) – agree? • bleeding = either Occ or C1, depending on what is meant (do you mean the process of bleeding, or the presence of blood that has escaped from the vascular system?) • rash = C1 • pharyngitis = C1 • spasm = either Occ or C0, depending on what is meant (the spasm occurrence, or the tendency to have repeated spasms)

26. Some test cases (2) Occ) occurrents (things that happen: exposures, accidents, events) C0) continuants that may exist even when their defining characteristic(s) is/are not present C1) continuants whose defining characteristics must always exist • deformities • abuse • victim of abuse (status) • adhesions • hypothermia • anemia • low hemoglobin

27. Some test cases (2) – agree? • deformities = C1 • abuse = Occ • victim of abuse (status) = C0 • adhesions = C1 • hypothermia = C1 • anemia = C0 (if you mean the category that includes aplastic anemia, etc) • low hemoglobin = C1

28. Some test cases (3) Occ) occurrents (things that happen: exposures, accidents, events) C0) continuants that may exist even when their defining characteristic(s) is/are not present C1) continuants whose defining characteristics must always exist • thrombosis • tic • hemifacial spasm • anxiety • anxiety disorder

29. Some test cases (3) – agree? • thrombosis = C1 • tic = either Occ or C0, depending on whether you mean the occurrence of the tic, or the tendency for the tic to occur. • hemifacial spasm = Occ or C0 • anxiety = C1 • anxiety disorder = C0

30. Some test cases (4) Occ) occurrents (things that happen: exposures, accidents, events) C0) continuants that may exist even when their defining characteristic(s) is/are not present C1) continuants whose defining characteristics must always exist • difficulty hearing • hearing disorder • vasovagal syncope • autoimmune thrombocytopenia • low platelet count • low platelet count due to autoimmune destruction

31. Some test cases (4) – agree? • difficulty hearing = C1 • hearing disorder = C0 • vasovagal syncope = Occ or C0, again depending on whether you mean the event of fainting, or the tendency to faint • autoimmune thrombocytopenia = C0. You can have autoimmune thrombocytopenia but have a transfused platelet level that is normal. • low platelet count = C1 • low platelet count due to autoimmune destruction = C1

32. Some test cases (5) Occ) occurrents (things that happen: exposures, accidents, events) C0) continuants that may exist even when their defining characteristic(s) is/are not present C1) continuants whose defining characteristics must always exist • apnea in the newborn • secretory diarrhea • difficulty hearing due to conductive hearing loss • lung cancer • malignant lung tumor

33. Some test cases (5) – agree? • apnea in the newborn = Occ or C0 • secretory diarrhea = C0, possibly Occ, depending on what you mean. • conductive hearing loss due to disorder of external ear = C0 (you still have it even if you put in a hearing aid that allows you to hear normally) • difficulty hearing due to conductive hearing loss = C1 • lung cancer = C0 • malignant lung tumor = C1

34. Some test cases (6) Occ) occurrents (things that happen: exposures, accidents, events) C0) continuants that may exist even when their defining characteristic(s) is/are not present C1) continuants whose defining characteristics must always exist • loss of voice • sense of smell altered • edema • calcified cataract • quadriplegia • pain • pain syndrome

35. Some test cases (6) – agree? • loss of voice = C1 • sense of smell altered = C1 • edema = C1 • calcified cataract = C1 • quadriplegia = C1 • pain = C1 • pain syndrome = C0

37. What to do about the “disorder” tag? • Keep it – no change • Revert to “finding” (the tag of the clinical finding hierarchy) • Change it to a tag (or tags) with reproducible meaning

39. What is a disease? Stedman's Concise Medical Dictionary for the Health Professions, 3rd Edition 1997. Williams and Wilkins: 1. An interruption, cessation, or disorder of body functions, systems, or organs. Synonym: illness, morbus, sickness. 2. A morbid entity characterized usually by at least two of these criteria: recognized etiologic agent(s), identifiable group of signs and symptoms, or consistent anatomical alterations. See also: syndrome. 3. Literally, dis-ease, the opposite of ease, when something is wrong with a bodily function

40. What is a disease? • Wikipedia: • A disease is any abnormal condition of the body or mind that causes discomfort, dysfunction, or distress to the person affected or those in contact with the person. Sometimes the term is used broadly to include injuries, disabilities, syndromes, symptoms, deviant behaviors, and atypical variations of structure and function, while in other contexts these may be considered distinguishable categories • So which are included and which aren’t? • Injuries: Paper cut? Skull fracture? • Discomfort: ingrown hair? Psychogenic pain? • Distress to those in contact with the person: bigotry, ignorance, low IQ?

41. What is a disease? CanadaPharma.org • Any abnormality of bodily structure or function, other than those arising directly from injury Oregon State University, anthropology glossary: • a pathological condition that is cross-culturally defined and recognized • excludes Karoshi, Gwarosa