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.
Short format in which partition identifiers are reserved for an organization which is permitted to issue any valid identifiers within the allocated partitions. The short format approach does not require a specific namespace identifier and is only applicable to components originated and maintained by the SNOMED International as part of the International Release of SNOMED CT.
Long format in which the partition identifier value indicates that a separate namespace identifier is required to distinguish between components originated as part of an extension created by an appropriately authorized organization .
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.