The permissible value for the SCTIDs are limited by the following rules:
- Only positive integer values that are greater than 105 and less than 1018 are permitted.
The only valid string renderings of the identifier value are String of decimal digits (0-9), commencing with a non zero digit.
The second and third digits from the right hand end of the string rendering of the identifier must match one of the partition-identifier values specified in this guide.
The rightmost digit of the string rendering is a check-digit and must match the value calculated using the specified check-digit computation.
Note
As a result of these rules, many 64-bit integers are not valid SCTIDs. The value limitations enable any valid SCTID to be stored in either a signed or unsigned 64-bit integer.
The rules also ensure that an SCTID can be distinguished from code from one of the antecedent code systems Read Codes(which are 4 or 5 characters in length) and legacy Identifiers from SNOMED RT and it predecessors (which always start with a letter).
SNOMED RT identifiers are SCTIDs identical to those used in SNOMED CT but in some cases will now refer to inactive concepts. In these cases, data in the 900000000000489007 | Concept inactivation indicator reference set| and 900000000000522004 | Historical association reference set| can be used to find the identifier of the closest equivalent active concept.
Warning
In some systems and frameworks the default numeric data type is a floating point representation according to IEEE 754. For example, as of today in JavaScript the number type (by default) is a double precision floating precision data type allowing representation of 53-bit integers, which is not sufficient for SCTIDs.
It is recommended that you specify a 64-bit integer type for representing SCTIDs rather than using a default numeric data type. Where a 64-bit integer data type is not available, please use a string data type to represent the SCTIDs.
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