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. 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 6.2-1: SCTID Short Format - Applicable to components originating from the International Release


Figure 6.2-2: 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.