Draft Editorial Guidance

Ambiguous Concept

• The inactivated concept is inherently ambiguous.
• It is important to differentiate between inherent ambiguity and "vagueness". If the FSN is vague consider using Meaning Unknown.
• Identify all of the POSSIBLY_EQUIVALENT_TO concepts, the sum of which should be semantically identical to the inactivated concept.
• Only in exceptional circumstances will it be acceptable to have only one POSSIBLY_EQUIVALENT_TO target and that is where the second target concept represents a concept that is considered to be of little or no clinical usefulness.
• Note: Non-synonymous synonyms should be inactivated and resigned before inactivating the ambiguous concept.

Classification Derived Concept

REPLACED_BY

PARTIALLY_EQUIVALENT_TO

• The inactivated concept originates from the “closed world” classification paradigm and as such is inappropriate content for use within the clinical record.
• These concepts often contain the expressions "not otherwise specified (NOS)", "Unspecified", "Otherwise specified", conjunction/disjunction, etc.
• REPLACED_BY should be used where the target replacement concept is of the same semantic category and have the same or less specificity than the inactivated concept. It will often be the same as the inactivated concept minus the "classification tail" of "other" or "NOS", etc.
• PARTIALLY_EQUIVALENT_TO should be used where there is a conjunction, (with or and) and must include all of the elements of the conjunction e.g. has a cardinality of 2 or more.

Concept Moved Elsewhere

ALTERNATIVE 

No suitable replacement identified

• Applies where jurisdictional control of a concept passes between extensions, or between the international edition and an extension (e.g. veterinary extension)
• Where the meaning of the concept to be inactivated is strictly jurisdictional e.g. relates to specific forms, branded products, legal entities, etc, no replacement is required and, therefore, no association type is allocated.
• ALTERNATIVE should be used where there is concern that the concept may have been used by members of the community of practice. The ALTERNATIVE substitute concept is offered as semantically "sufficiently similar" to the original concept for some use cases that should be specified by the end-user. 

Duplicate Concept

SAME_AS

• The inactivated concept semantically represents exactly the meaning of the remaining active concept and therefore the association is "SAME_AS".
• Note that the meaning of the concept is based on the FSN but does not imply that the FSNs are identical.

Erroneous Concept

REPLACED_BY

• The inactivated concept has an FSN which contains an error that when corrected potentially changes the semantic meaning of the concept.
• NOTE: Where the error is grammatical or a spelling mistake which when correct does not change the meaning, the description rather than the concept should be inactivated. 

Meaning Unknown

No association required

• The meaning of the inactivated concept cannot be determined.
• It will normally be necessary to search the clinical literature to establish that this is truly an unknown concept rather than an outdated clinical concept.
• This inactivation reason may be used where the meaning of the FSN is considered to be vague.

Non-Conformance to Editorial Policy

REPLACED_BY

ALTERNATIVE

No suitable replacement identified

• The inactivated concept does not comply with the current or updated Editorial Policy.
• Where conformance to editorial policy potentially changes the meaning of a concept and it is possible to replace this with a concept that is semantically very close to the inactivated concept the association should be REPLACED_BY. e.g. a radiological procedure which in practice almost exclusively uses contrast but this wasn't included in the FSN would be inactivated and REPLACED_BY the new concept in which the FSN clearly states the use of contrast.
• Where the change to editorial policy results in a change in scope of SNOMED CT then it may be possible to provide a target replacement that is similar to but less specific than the inactivated concept and therefore the association would be ALTERNATIVE. e.g. where branded products were considered out of scope for SNOMED CT an ALTERNATIVE would be the generic product.
• In some instances, a suitable replacement cannot be identified e.g. should a decision be taken to count occupations as out of scope for SNOMED International Edition.

Outdated Concept

REPLACED_BY 

POSSIBLY_REPLACED_BY

No suitable replacement identified

• The inactivated concept is an outdated concept that is no longer considered to be clinically acceptable or semantically interoperable internationally.
• A REPLACED_BY association would be used where there exists a concept that is semantically similar to or more general than the inactivated concept for the purposes of data healing and analysis of historical data.
• Where there has been an update to a disorder classification, a substance or organism originally believed to be a single entity has, following further study, been reclassified as 2 or more substances or organisms. Where 2 or more potential replacements exist use POSSIBLY_REPLACED_BY for each of the target concepts.
• In some circumstances, an outdated concept simply falls into disuse without any appropriate replacement.

For the Author:

• The SAME_AS association type exists to declare when any pair of different concept identifiers in fact represent exactly the same semantics. They are true semantic duplicates, for all time.
• Because of this statement of unambiguous and exact, bidirectional semantic equivalence, (A) SAME_AS (B) explicitly implies that everything ever subsequently said about B is, by definition, also true of A. (And, technically, also vice versa though, since A is inactive, nothing new should ever be said about it)

Implications for the vendor/user:

• Given that the inactivated concept is semantically equivalent to the retained concept there should be no requirement for the user to review the replacement.

For the Author:

• The POSSIBLY_EQUIVALENT_TO association is to be used where an inactive concept was previously the conflation or disjunction of two or more distinct possible meanings, at least one of which is also now represented as a current SNOMED concept.
•  The implication of a set of POSSIBLY_EQUIVALENT_TO associations is that all possible EHR instances previously coded to the inactivated code can be re-coded to one or other of the listed association concepts, without exception and also without either adding or losing any semantics not already expressed by the original coding. No other active concept exists that would more precisely capture what was expressed by a clinician originally selecting the inactivated code.

Implications for the vendor/user:

• Where a POSSIBLY_EQUIVALENT_TO association is encountered this implies that a decision is to be made by the end-user as to which of the available POSSIBLY_EQUIVALENT_TO associations correctly represents the original meaning stated by the clinician.
• The vendor must provide adequate tooling to enable the end-user to view all of the POSSIBLY_EQUIVALENT_TO associations and select the most appropriate one to replace the inactivated concept.

PARTIALLY_EQUIVALENT_TO

For the Author:

• The historical association PARTIALLY_EQUIVALENT_TO explicitly states; when a concept that contains conjunction using “WITH” or “AND” is inactivated each of the individual elements of the conjunction is replaced by semantically equivalent clinical concepts using an association type of “PARTIALLY_EQUIVALENT_TO”. Where an element does not currently exist within SNOMED CT it must be created to ensure exact semantic equivalence between the inactivated concept and the sum of its replacements.

Implications for the vendor/user:

• "PARTIALLY_EQUIVALENT_TO"  signifies to the implementer and end-user that the single inactivated concept MUST be represented within the clinical notes by ALL of the PARTIALLY_EQUIVALENT_TO targets.

REPLACED_BY

For the Author:

• The purpose of the REPLACED_BY association type is to indicate that the suggested target replacement concept is NOT semantically equivalent to the inactivated concept (i.e., SAME_AS cannot apply). The target concept chosen should normally be of the same semantic category and have the same or less specificity than the inactivated concept.
• The stated REPLACED_BY target represents an alternative which, although not semantically exactly the same, is considered to be clinically useful and - in the judgment of the author/editor - represents the intended original meaning of the inactivated concept closely enough for some unspecified data processing use cases, most likely data repair in the context of data retrieval.

Implications for the vendor/user:

• Given that the REPLACED_BY association target is not semantically equivalent the end-user should be offered the opportunity to provide an alternative replacement that better represents their intended meaning.

POSSIBLY_REPLACED_BY

For the Author:

• The purpose of the POSSIBLY_REPLACED_BY association type is to indicate BOTH that none of the suggested target replacement concepts are semantically equivalent to any meaning implied by the inactivated concept (ie neither SAME_AS nor POSSIBLY_EQUIVALENT_TO can apply) AND that more than one potential replacement exists, only one of which will be appropriate.
• The stated POSSIBLY_REPLACED_BY targets represent all of the alternatives identified as a result of the reclassification process, one of which, although not semantically exactly the same as the inactivated concept, is considered to be clinically acceptable for each individual patient previously coded to the inactive concept.

Implications for the vendor/user:

• Where a POSSIBLY_REPLACED_BY association is encountered this implies that a decision is to be made by the end-user as to which of the available POSSIBLY_REPLACED_BY associations most closely represents the original meaning stated by the clinician.
• The vendor must provide adequate tooling to enable the end-user to view all of the POSSIBLY_REPLACED_BY associations and select the most appropriate one to replace the inactivated concept.
• Because the offered replacements are not semantically equivalent to the inactivated concept the end-user should be given the opportunity to provide an alternative replacement that better represents their intended meaning.

ALTERNATIVE

For the Author:

• The identified ALTERNATIVE substitute(s) are offered as semantically "sufficiently similar" to the original inactive concept, for certain unspecified use cases.

• In most circumstances, the ALTERNATIVE concept is likely to be a grouper concept a few levels higher up the hierarchy.

Implications for the vendor/user:

• The user should decide whether the alternative provided is appropriate for their use case and if necessary or appropriate replace it with a concept of their choosing