Draft Editorial Guidance

Introduction

SNOMED CT is a dynamic and evolving terminology in which the content must remain concurrent with current clinical practice and our evolving understanding of disease processes and treatments. As a result, content may change, become outdated, or as a result of improved understanding needs remodeling. However, individual patient records are created at a point in time and may use concepts that later become inactivated and replaced. For legal reasons, it is important that the concepts used at the time the record was made should persist over time so that records made prior to a change in the status of that concept remain available to extraction routines for population analysis and more importantly to ensure that individuals do not get lost to routine follow-up for ongoing care etc.

Managing and making transparent the history of a given concept over time is the responsibility of SNOMED International and this is achieved through the concept inactivation process. In order to make the process transparent, it is necessary to clearly document the reason for a given change in the status of a concept and provide vendors and users with the information necessary to understand those changes. Vendors can then use this information in such a way as to protect the meaning encapsulated in the individual's clinical record over time and ensure that decision support, routine analysis, and population studies can continue consistently and without risk to clinical safety.

There are two key elements to the inactivation process, firstly allocating an appropriate reason for the concept inactivation and secondly providing a clear understanding of the level of semantic equivalence through the historical association link between the inactivated concept and its replacement where it exists. To further improve the quality of our own audit trail additional information and links to reference sources can be added within text fields that accompany each inactivation.

The vendor can use the historical association 'type' to understand the level of semantic equivalence between the inactivated concept and its replacement and as a guide to what action should be taken by the end-user in updating their patient records and routine extraction routines in response to each inactivation.

Below is a summary of the inactivation reasons and the meaning of each of the historical associations and their implications for vendors/users. The link to the detailed guidance for each inactivation reason is provided.

Inactivation Reasons

Inactivation Reason	Association	Summary Definition
Ambiguous Concept	POSSIBLY_EQUIVALENT_TO	The inactivated concept is inherently ambiguous, and each of the potential meanings represented by the concept is semantically identical to at least one other clinical concept.
Classification Concept	REPLACED_BY EQUIVALENT_TO	The inactivated concept originates from the “closed world” classification paradigm and as such is inappropriate content for use within the clinical record.
Concept Moved Elsewhere	ALTERNATIVE No suitable replacement identified	The jurisdictional control of a concept passes between extensions, or between the international edition and an extension.
Duplicate Concept	SAME_AS	The inactivated concept semantically represents exactly the meaning of the remaining active concept. Note that the meaning of the concept is based on the FSN.
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.
Meaning Unknown	No association required	The meaning of the inactivated concept cannot be determined.
Non-Conformance to Editorial Policy	REPLACED_BY ALTERNATIVE No suitable replacement identified	The inactivated concept does not comply with the current Editorial Policy and when updated to comply with the policy potentially changes the semantic meaning of the concept.
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.

Historical Associations

Association	Summary Definition
SAME_AS	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.
POSSIBLY_EQIVALENT_TO	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.
EQUIVALENT_TO	For the Author: The historical association 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 “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: "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 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

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Draft Editorial Guidance

Introduction

Inactivation Reasons

Historical Associations

Editorial Guidance