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Narrative description:

The concept is considered to be ambiguous when there is the potential for a user to interpret the meaning in more than one way. This may arise due to inherent conflict between or within the descriptions, where the modelling of the concept does not reflect the meaning of the FSN or where the subtypes or supertypes imply that the concept has been misplaced.

Details:

Ambiguity may be apparent for a number of reasons:

• The FSN is ambiguous

• , where "ambiguous" carries the strict interpretation of: has more than one distinct and individually unambiguous interpretation. The most obvious form of ambiguous FSN is one that contains an explicit disjunction, for example 178841003 Complex reconstruction operations on hand and foot, where 'and' almost certainly really means 'or'. The ambiguous nature of this code is perhaps most easily revealed if we consider the universe of all patients with an EPR entry of 178841003, and then ask which should be returned in response to a query for all patients who have had a <<112746006 Operative procedure on hand ? Of course, we don't know; some had a foot operation. This thought experiment is "diagnostic" of an ambiguous term.
  
  Note that this therefore precludes using Ambiguous in cases where nobody knows what the FSN means at all, and so no active concept(s) can be identified that precisely correspond to even one of its distinct meanings. For example, 194964003 Milk spots of pericardium is clearly some kind of pericardial disorder or sign, but exactly what has long been lost in the mists of medical time. However, as far as we know, this term only ever had one clear and unambiguous meaning  - we just don't know what it was. The reason for inactivation of such concepts should be stated to be Outdated, or possibly "reason not stated". But not Ambiguous.
  
  
• A special case of a concept with more than one possible unambiguous interpretation concerns where there is a mismatch between an apparently unambiguous FSN, and the modelling assigned to the same concept. In this scenario, the set of ancestors and descendants (if any) computed by a reasoner for the concept will be inconsistent with what is implied by the FSN. Mismatch patterns will therefore include: 
  • Modelling is for a completely different category to the FSN meaning; this obviously includes where a concept needs to be moved to a different top-level hierarchy (except when between permitted pairs of top-level hierarchy)
  • Modelling is semantically more precise than the FSN meaning
  • The FSN meaning is semantically more specific than the

• • modelling; inactivation is determined case-by-case as this could simply be a primitive concept which cannot be defined
    

• Where the existing FSN is for the common name of an organism, changing it to the scientific name in the scenario where the same common name is in fact also associated with more than one other species provided that the scientific name was not already present as a synonym on the concept. Even if the scientific name was already also present but as a synonym, and even if the taxonomic position of the concept clearly also implies the same specific species, the concept remains intrinsically ambiguous because the "common name" form of FSN is not specific.

POSSIBLY_EQUIVALENT_TO association reference set (foundation metadata concept)

Known issues:

1. The presence of ambiguity implies that the concept could have more than one meaning, however, there may not be available concepts within SNOMED CT which match exactly all of the possible meanings.
2. While a concept may have more than one meaning it is possible that one or more of the meanings are considered not to be clinically useful and therefore only one target concept is considered to be appropriate.
3. Where there is ambiguity between the FSN and attached synonyms a judgement needs to be made as to whether it is better to inactivate the concept and create new concept(s) or inactivate the non-synonymous synonyms and link them to concepts which are semantically equivalent

Examples

Simple Example

269388002 Burn of eye (& [cornea]) (disorder)
MAY BE 282752000 Injury of eye region (disorder)
MAY BE 284542003 Burn of eye structure (disorder)
MAY BE 274204004 Corneal burn (disorder)

112524000 Northern barred owl (organism)
MAY BE 396690003 Strix varia (organism)
MAY BE 423927009 Strix varia varia (organism)

16704000 Repair AND revision of stoma of esophagus (procedure)
MAY BE 386697002 Repair AND revision of stoma of esophagus (procedure)
MAY BE 386695005 Repair of stoma of esophagus (procedure)
MAY BE 386698007 Revision of esophagostomy (procedure)

267940001 Joint effusion of the forearm (disorder)
MAY BE 202373004 Elbow joint effusion (disorder)
MAY BE 202375006 Wrist joint effusion (disorder)

239801005 Juvenile rheumatoid arthritis (disorder)
MAY BE 410795001 Juvenile rheumatoid arthritis (disorder)
MAY BE 410796000 Juvenile seropositive polyarthritis (disorder)

236568008 Renal transplant disorder (disorder)
MAY BE 58797008 Complication of transplanted kidney (disorder)
MAY BE 429451003 Disorder related to renal transplantation (disorder)

85062008 Isopropyl alcohol (substance)
MAY BE 259268001 Isopropyl alcohol (substance)

228318004 Regular drinker (finding)
MAY BE 365968000 Finding of drinking habits (finding)
MAY BE 228320001 Habitual drinker (finding)

78765007 Intrauterine device (physical object)
MAY BE 268460000 Intrauterine contraceptive device (physical object)
MAY BE ???

195746005 Recurrent chest infection (disorder)
MAY BE 448739000 Recurrent lower respiratory tract infection (disorder)
MAY BE ???

28746002 Recurrent apnea (finding)
MAY BE 1023001 Apnea (finding)
MAY BE 416945002 Recurrent apnea (finding)

Impact:

•  Authors

•  Release Management Team

•  Developers

1. Review and update refsets
2. Provide an appropriate user interface to enable the user to choose the appropriate replacement concept from the options provided

•  End Users

1. If the end user agrees the component is ambiguous then a decision needs to be made as to which option to choose on a case by case basis

2. If the end user disagrees that the component is ambiguous, then a suitable replacement SNOMED component will be needed.

Proposed improvement:

1. Resolve non-synonymous synonyms by inactivation of the descriptions and re-assign to either existing concepts which are semantically equivalent or by creating new concepts
2. Establish whether the ambiguous FSN requires 2 or more clinically useful concepts in order to maintain semantic equivalence. If 2 or more concepts are required use the association type of "POSSIBLY_EQUIVALENT_TO.
3. If after due diligence only one target is considered to be clinically useful then the association type should be 'REPLACED_BY'
4. Update the tooling to support the allocation of a "REPLACED_BY" association with a text field to explain the reason(s)

Supporting resources: