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Each SCTID identifies a SNOMED CT component. The identifier itself does not contain information related to the meaning of a concept or description. This means it is not possible to infer anything about the meaning of a concept from the numeric value of the identifier or from the sequence of digits in that form of the identifer. The meaning of a concept can be determined from relationships to other concepts and from associated descriptions that include human readable terms.

The SCTID does however have a structure which includes valuable information about the nature and source of the identified component and the validity of the identifier. This structure supports the following features:

  • Check-digit validation of the identifier.

    • The check-digit is the final digit in the decimal rendering of the identifier. This can be checked to minimize errors from transcription or incomplete copy-paste actions.

  • Partitioning between identifiers for different types of SNOMED CT component.

    • A two-digit partition-identifier distinguishes the identifiers of different component types and prevents the same identifier from being allocated to both a concept and a description. As a result, when an SCTID is read from a record or other resource, it is possible to determine whether it represents a concept, a relationship or a description, before searching for the identified component.

  • Namespaces to separate component identifiers originated by different organizations. 

    • Organizations are only permitted to issue identifiers which fall within a specified namespace of potential identifier values. This prevents collisions between identifiers issues by different organizations which would otherwise result in ambiguity and errors when sharing data.

    • There are two formats used for representing namespaces. 


Figure 5.2-1: SCTID Short Format - Applicable to components originating from the International Release


Figure 5.2-2: SCTID Long Format - Applicable to components originating from a SNOMED CT Extension

The SNOMED International allocates namespace-identifiers to organizations such as Members and Affiliates to enable them to create content and or derivatives in an extension. The namespace-identifiers enables unique  SCTID to be issued by many organizations and allow each  SCTID to be traced to an authorized originating organization.