Current Version - Under Revision
In some cases, during or after the merger of SNOMED RT and NHS Clinical Terms Version 3 some concept in SNOMED RT were found to be ambiguous or duplicated. Even in these cases the concepts with original identifier are still present in the SNOMED CT Concepts Table but have been inactivated. Records in the Concept Inactivation Reference Set indicate the reason for inactivation and records in the appropriate Historical Association Reference Set can be used to locate the appropriate active concept identifier.
For information about historical reference sets please see the following:
These Associations can be used either to allow concepts recorded using these identifiers to be recognized by retrieval tools or to enable mapping of the stored information to the appropriate active concepts.
If any stored Concept Identifier of an Inactive Concept is mapped to an active Concept Identifier using these Associations it is strongly recommended that the original Concept Identifier is also retained. This enables future improvements or corrections of such mappings if revised Associations are present in a future release of SNOMED CT .
In addition, SNOMED RT contained both generic and brand name drugs for the US. A decision was made during the merger process to not retire these concepts using the extension mechanisms, but to place these components directly in the US Drug Extension . Therefore to access all SNOMED RT components you will need to use the US Drug Extension in addition to the SNOMED CT International Release .