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Current Version - Under Revision

Migration from  SNOMED RT poses very few significant issues, since many features of the design of  SNOMED CT including the use of  SCTIDs were incorporated into  SNOMED RT.

Thus transition to  SNOMED CT for users of  SNOMED RT is relatively straightforward because the Concept Identifiers in  SNOMED RT are the same as the uses in  SNOMED CT.

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For information about historical reference sets please see the following: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



In addition,


contained both generic and brand name drugs for the US. A decision was made during the merger process to not retire these


using the


mechanisms, but to place these components directly in the US Drug


. Therefore to access all

SNOMED RT components

you will need to use the US Drug


in addition to the

SNOMED CT International Release






also contains the appropriate legacy SNOMEDID from

SNOMED International


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