Policy on case sensitivity of codes
Policy on Case Sensitivity of Codes
Publishers of Code Systems and their content have a source of truth for each published version. For those code systems whose codes (primary concept identifiers, to be carried in the code property of the v3 CD and its specializations, or in the code component of the v2 CNE and CWE datatypes, or in the code attribute in the concept resource in FHIR) contain alphabetic characters rather than solely numeric characters, case of the letters in the code string (uppercase/lowercase) may be significant.
The case of the characters to be carried in the HL7 data structure should match the case in which the identifying concept representation is published by the code system publisher in their source of truth.
In the rare circumstance where the code system publisher is not consistent in the case of the identifying concept representation across the code system or across versions, the code system should be considered case insensitive, and particular implementations should document what they have used. Even in these cases, the code carried in the HL7 structure should match what is published by the code system publisher.