SNOMED CT has an international and multilingual scope but can be localized to represent meanings and terms unique to particular organizations or localities. A National Extension includes content outside of the scope of the International Release, but necessary for national conformance and interoperability. Each member-state determines the application and interpretation of this scope and whether or not concepts should be added to their extension.
National Extension criteria include affirmative answers to the following:
Extensions are created, structured, maintained, and distributed in accordance with SNOMED CT specifications and guidelines to ensure compatibility with the SNOMED CT International Release. Members may create, maintain, and distribute extensions to address specific national, regional, and language requirements. Affiliates may also create, maintain, and distribute extensions to meet the needs of particular software solutions and customers. Content that is within the scope of the International Release is restricted to the International Release and may not be modified or replaced by an extension, unless explicitly permitted by SNOMED International. Please see the Practical Guide to Extensions for more information.
SNOMED CT is not intended to cover all medical knowledge. Content that is strictly related to animals is out of the scope of the SNOMED CT international release. Non-human content may be included in a request for new content via the SNOMED International Content Request System (CRS) or may be identified in the International Release. Careful consideration is required to differentiate content that belongs in the International Release versus an extension. The basic principle is that content used in human medicine should be in the core. Content that is strictly non-human may be managed in an extension.
Examples of non-human content,
Types of content that should be in the core include the following:
The Veterinary Extension is publicly available to SNOMED International member countries and to Affiliate Licensees. To access to the Veterinary Extension, please see http://vtsl.vetmed.vt.edu, or contact the VTSL at email@example.com.
Classification-derived phrases are not accepted. Concepts with unclear, unspecified, or ambiguous meaning should not be used. Rejections are expected for requests with the following phrases:
Concepts referring to regulatory status or characterization (e.g., over-the-counter) are out of scope for the International Release. Meaning may vary by jurisdiction and may not be consistent internationally.
A person's citizenship or legal residence is not an intrinsic characteristic of a person and is out of scope. SNOMED International recommends use of ISO country codes for recording residency.
Because of the jurisdictional and administrative aspects of medical insurance, this has been deemed out of scope for the SNOMED CT International release. It is up to individual member countries to determine if that type of content should be included in their extensions. Users should contact their country's extension administrator to determine if this type of content is acceptable.