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Purpose
The Code to Expression type reference set is used meet the requirements for representation of associations between codes in another code system and SNOMED CT expressions, where the following requirements apply:
- Some or all of the codes in the other code system cannot be mapped to an individual SNOMED CT concept but can be associated with (i.e. mapped to) a postcoordinated SNOMED CT expression which convey the same meaning, or at least a similar meaning.
- A requirement that SNOMED International shall not systematically add missing content to enable a single SNOMED CT identifier to represent the meaning represented by the codes in the other code system.
- A requirement to indicate the degree of correlation between the code in the other code system and the SNOMED CT expression.
- A requirement to indicate the code in the other code system was created before any single concept representation in SNOMED CT or whether the single concept representation in SNOMED CT predated the creation of the association.
- No requirements for mapping rules or advice to be included with each association or map.
Design
The Code to Expression type reference set is designed to meet the requirements as they apply to the associations between LOINC Term Codes and SNOMED CT expression.
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- correlationId attribute – retained to meet requirement (c).
- contentOriginId attribute – retained to meet requirement (d).
Expression Format
Each expression conforms to the SNOMED CT Composition Grammar. For further details of the syntax please see the Compositional Grammar - Specification and Guide (http://snomed.org/scg). The expression represents the SNOMED CT definition of the LOINC Term based in the recently developed concept model for the
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LOINC Term Code Status Changes
Deprecated statuses will cause the expression associations to be marked as inactive but trial use status will not be represented. LOINC Terms that were already deprecated at the time of initial mapping will not be included in maps and associations. However, dependent on demand and priority to assessments, it is possible these may be added later.
Code to Expression Reference Set Data Structure
Field | Data type | Purpose | ||||||||||||||
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id |
| A 128 bit unsigned integer, uniquely identifying the reference set member. | ||||||||||||||
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| Specifies the inclusive date at which this change becomes effective. | ||||||||||||||
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| Specifies whether the member's state was active or inactive from the nominal release date specified by the effectiveTime field. | ||||||||||||||
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| Identifies the member version's module. Set to a child of |Module| within the metadata hierarchy. | ||||||||||||||
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| Identifies the reference set. | ||||||||||||||
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| A reference to a SNOMED CT metadata concept referring to the
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| The value of the LOINC Term Code associated with the expression. | ||||||||||||||
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| A reference to the SNOMED CT concept being mapped to/from the LOINC Term Code. | ||||||||||||||
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| Indicates whether or not the expression contains a sufficient definition of the LOINC Term Code in the mapTarget field.
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| The correlation between the SNOMED CT expression and the LOINC Term Code.
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| Indication of whether concept was initially in one of the terminologies (LOINC or SNOMED CT) and added to the other as part of mapping or was in both terminologies at the outset. Values are subtype children
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Metadata
Refset Name
The following metadata in the "Foundation metadata concept" hierarchy supports this reference set:
| Scg expression | ||
|---|---|---|
| ||
900000000000454005 | Foundation metadata concept | 900000000000455006 | Reference set | 705109006 |Code to expression type reference set| 705110001 |LOINC Term to Expression reference set| |
Values for definitionStatusId
| Scg expression | ||
|---|---|---|
| ||
900000000000444006 | Definition status | 900000000000074008 | Necessary but not sufficient concept definition status | 900000000000073002 | Sufficiently defined concept definition status | |
Values for CorrelationId
Suggestion is use of current values set. However, an argument can be made in favor of duplication of the hierarchy with "source code" replaced by "expression".
| Scg expression | ||
|---|---|---|
| ||
447247004 | SNOMED CT source code to target map code correlation value| 447559001 | Broad to narrow map from SNOMED CT source code to target code | 447557004 | Exact match map from SNOMED CT source code to target code | 447558009 | Narrow to broad map from SNOMED CT source code to target code | 447560006 | Partial overlap between SNOMED CT source code and target code | |
Values for ContentOriginId
| Scg expression | ||
|---|---|---|
| ||
705116007 | Original code system source for linked content value | 705117003 |Originally in LOINC| 705118008 |Originally in SNOMED CT| 705119000 |Originally in both LOINC and SNOMED CT| |
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