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Table 3.7.3-1 summarizes change management issues that may affect and EHR application when moving to a new version of a SNOMED CT edition. It also outlines approaches to checking for and resolving issues of different types.

Table 3.7.3-1: Impact of Version Updates on EHR Applications

Change TypeSignificanceRisksFactors Affecting Risk Level and Likely ImpactChange Management Actions
Addition of a concept

MODERATE

The new concept may not be available in some data entry contexts.

Although all new concepts will be available for ad-hoc searches, it may not be possible to enter a new concept in data entry fields with tightly defined value set bindings.

Risk is higher if the value set binding specifies members of a reference set or individual concepts. Value set bindings that use hierarchy-based constraints are more likely to include new concepts that are appropriate to the data entry context.

Review newly added concepts paying particular attention to concepts in areas of the hierarchies that are frequently used.

Consider if new concepts need be added to any reference sets, search constraints, user interface terminology bindings or queries.

Recommendation

Mitigate the risk of excluding new concepts by using hierarchy constraints, rather than subsets or lists of individual concepts. These will automatically include new concepts that conform to the constraint minimizing the need for manual intervention.

Inconsistent reporting and analytics may occur. This is a risk if a new concept has not been included in a reporting query criteria.

Risk is higher if reporting queries enumerate members of a reference set or specify each concept individually. Queries that use hierarchy-based constraints are more likely to include new concepts that are relevant to the report.

Inactivation of a concept

HIGH

Inactive concepts may be explicitly referenced by user interface terminology bindings. This can lead to one of the following errors:

  • The inactive concept being included in a new records (this is a serious error); or
  • The system correctly prevents addition of the inactive concept and it becomes impossible to record a significant item of data.

Risk is higher if the value set binding specifies members of a reference set or individual concepts. Value set bindings that use hierarchy-based constraints will automatically exclude inactive concepts.

Check whether any inactivated concepts are used in user interface terminology bindings. Use the reason for inactivation to inform decisions on an appropriate approach to resolution. Update these bindings to remove references to inactive concepts, preferably replacing them with appropriate active concepts identified using historical associations from the replaced concept. For medicolegal reasons these changes should only affect newly entered record.
Inactive concepts may be referenced in query criteria used for reporting and analytics. This may cause significant changes to the results of those queries, as concepts previously subsumed by (or defined by reference to) this concept may no longer be included.Risk is higher if the reference to the concept is part of a subsumption constraint. Individual references to the inactive concept will not result in changes to the report output.Check query criteria used for reporting and analytics for references to inactive concepts. If necessary, adjust the query criteria to delivery intended results (e.g. by excluding inactive concepts).

Inactive concepts may be present in EHR record entries that were created when the concept was active. The existence of an inactive concept in earlier record entries is not an error. However, as the concept is no longer active it will not be subsumed by other concepts and will be excluded from the results of queries that formerly included it.

Use of concepts that are later inactivated. This is a particular issue if the concept is inactivate due to ambiguity because in this case there is no single equivalent active concept.

Review inactivated concepts to determine whether they were previously subsumed by queries used for reporting or analytics. Use the reason for inactivation to inform decisions on an appropriate approach to resolution.

Choose an appropriate approach to resolve any potential reporting anomaly. Some possible resolutions are suggested here:

  • Explicitly include the inactive concept in queries that formerly included it so historical data is still reported consistently.
  • Create a reference set containing inactive concepts that were previously included in the result of a query and where appropriate include members of that reference set in query criteria.
  • Use historical associations to extend normal subsumption so that inactive concepts are included whenever their active equivalent concepts are included. In the case of associations in the 900000000000523009 | POSSIBLY EQUIVALENT TO association reference set| this approach may need to be more carefully reviewed and selectively applied.
  • Accept the exclusion of the now inactive concept from reports.
  • Map the intended meaning of the original (now inactive) concept to an active concept and add that to the record in a way that allows it to be appropriately included in reports. For medicolegal reasons this should be an addition to and not a replacement of the record.
Change to a concept

NONE

The only mutable concept data attribute in the release file is definitionStatusId. If the value changes this indicates a change in the definition. However, in itself a change to the definitionStatusId is not significant1.

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Addition of a description

LOW

Makes a new display term available for a concept. This may simply be another option. However, other changes, such as inactivation of other descriptions or changes in language acceptability, may make it necessary to use the new description.

The impact of addition of a new description is minimal unless other descriptions are inactivated or are no longer marked as preferred or acceptable in the relevant language reference set.

Description added to a new concept:

  • By default the description used to display a new concept should be the preferred term in the selected language or dialect.
  • Alternative descriptions may be displayed if they are more appropriate to the context or selected by a user.

Description added to an existing concept:

  • Should have no impact on existing stored data.
  • May be considered as an alternative display term in data entry template or reports.
Change to a description

LOW

Changes to the term and/or caseSignificantId are possible. However, quality assurance rules should limit the range of possible changes to the term in a description.


Changes to descriptions used as display terms in data entry templates or reports.

Review data entry templates and reports that use a changed description as a display term:

  • Update the display term to match any change to the term.
  • Update the term if the use of upper and lower case does not conform to the options permitted by the caseSignificanceId.

In general, terms stored in existing patient records should not be updated based on terminology changes2.

Inactivation of a description

HIGH

An inactivated description cannot be used as the source of a display term for data entry or reporting.

Review any use of terms that are associated with:

  • Descriptions that are inactive
  • Descriptions that are no longer acceptable or preferred in a selected language reference set.

In these cases, replace the use of this term in data entry interfaces with a term for the same concept that is either preferred or acceptable in the selected language reference set. Similarly, if a term is stored with the selected concept, ensure that the term stored is also preferred or acceptable in the selected language.

In general, terms stored in existing patient records should not be updated based on terminology changes2.

Change to the acceptability of a description in a language refset used by the application

MODERATE

A description that is not acceptable for use in one or more of the languages or dialects used in the EHR system, must not be used as the source of a display term for data entry or reporting.

Additions, changes and inactivations of relationships

MODERATE


Relationships represent the inferred necessary normal form definition of a concept. OWL axiom reference set members represent the stated definitions of concepts.

Additions, changes or inactivations of either of these components, represent changes to the definition of a concept. A change in the definition of a concept also affects other concepts with a definitions that refer to that concept.

The impact of changes to concept definitions depends on the way these changes affect the results of expression constraints and queries used in data entry templates, reporting and analytics.



Review value set bindings, expression constraints and queries used in reports or analytics and identify the expression constraints on which these depend.

For each of these constraints that may have been affected by these changes apply the steps shown in Table 3.7.3-2. Where appropriate fake the actions outlined in Table 3.7.3-3 to address any unintended or unwanted effects arising from the update.



Additions, changes and inactivations of OWL expression refset members
Additions, changes or inactivations of reference set members

MODERATE

Expression constraints and queries may include or exclude members of a reference set. Additions of new members or inactivation of existing members can therefore alter the results of expression constraints and queries used in data entry templates, reporting and analytics.

Table 3.7.3-2: Comparing Results of Applying an Expression Constraint to Two Versions of a SNOMED CT Edition

StepInputOutput DescriptionOutput Name
Identify snapshot views of two versions fo the same SNOMED CT editionCurrent editionEdition in use before planned updateV1-snapshot
New editionEdition to be used after planned updateV2-snapshot
Apply the Expression Constraint (ECL) to each version to identify two subsets of concepts that conform to the constraint.V1-snapshotSet of concepts in V1-snapshot that conform to the ECLV1-ECL-result
V2-snapshotSet of concepts in V2-snapshot that conform to the ECLV2-ECL-result

Compare the subsets created by the previous step to identify two subsets that containing concepts that conform to the constraint in one of the versions but do not conform in the other version.

V1-ECL-resultConcepts in V1-ECL-result but not in V2-ECL-resultV1-ECL-only
V2-ECL-resultConcepts in V2-ECL-result but not in V1-ECL-resultV2-ECL-only

Subdivide the subset of concepts that only conform to the constraint in the current version into two subsets depending on the active status of the concept in the new version.

V1-ECL-onlyConcepts in V1-ECL-only that are active in V2-snapshotV1-ECL-only-V2-active
V1-ECL-onlyConcepts in V1-ECL-only that are inactive in V2-snapshotV1-ECL-only-V2-inactive

Subdivide the subset of concepts that only conform to the constraint in the new version into three subsets depending on whether the concept is present in the current version and if so depending on the active status of the concept.

V2-ECL-onlyConcepts in V2-ECL-only that are active in V1-snapshotV2-ECL-only-V1-active
V2-ECL-onlyConcepts in V2-ECL-only that are inactive in V1-snapshotV2-ECL-only-V1-inactive
V2-ECL-onlyConcepts in V2-ECL-only that are absent from V1-snapshotV2-ECL-only-V1-absent

Check the content of the five sets of concepts generated by the last two steps using the notes in Table 3.7.3-3

Table 3.7.3-3: Evaluation of Differences between ECL Results

Output NameDescription
ImpactRecommended Action
V2-ECL-only-V1-absent

New concepts in V2 release that were not present in V1.

  • Inclusion of these concepts will not affect retrospective reports or analytics because the new concepts could not have been used previously3.
  • Inclusion of these new concepts is appropriate as they conform to the stated constraint.

NONE

None

V2-ECL-only-V1-inactive

It is unusual for concepts to be reactivated so this set will usually be empty.

Concepts reactivated in V2 release after being inactive in V1 release. However, in theory this could alter the result of retrospective reports because reactivation of the concept causes these concepts to be included whereas previously they were excluded.

LOW

If this subset contains any concepts, be aware that this may affect result of rerunning an earlier reports or analytics on retrospective data. However, in most cases no action is required.

V2-ECL-only-V1-activeConcepts that only conform to the ECL in V2 although they are active in both versions. Retrospective reports will now include concepts that were previously excluded from the report.

HIGH

Concepts in this subset will be included in reports or analytics performed after upgrading to the new version but would not have been included when using the current version.

This may be due to an revision of concept definitions or addition of concepts to a reference set. Assuming these changes were intentional improvements the revised result should be more accurate and more complete.

In some cases, this type of change may have unintended consequences. Therefore a review of the context in which these constraints are used is recommended. If necessary the constraint can then be refined to exclude some or all of the added concepts.

V1-ECL-only-V2-activeConcepts that only conform to the ECL in V1 although they are active in both versions. Retrospective reports will now exclude concepts that were included in the report.

HIGH

Concepts in this subset will be excluded from reports or analytics performed after upgrading to the new version but would have been included when using the current version.

This may be due to an revision of concept definitions or removal of concepts from a reference set. Assuming these changes were intentional improvements the revised result should be more accurate.

In some cases, this type of change may have unintended consequences. Therefore a review of the context in which these constraints are used is recommended. If necessary the constraint can then be refined to specifically include some or all of the excluded concepts.

V1-ECL-only-V2-inactive

Concepts that only conform to the ECL in V1 that are inactive in V2. In this case, inactivation of the concept means that retrospective reports will exclude these concepts that were previously included in the report.

MODERATE

Concepts in this subset will be excluded from reports or analytics performed after upgrading to the new version but would have been included when using the current version.

In this case, the reason for exclusion is that the concept is inactive rather than being a direct consequence of the constraint. There are two ways to enable an inactive concept to be included to conform to a constraint. A direct reference to a concept identifier or a reference to the members or a reference set that includes that concept4.


Footnotes
The definitionStatusId fields has two possible values: 900000000000073002 | Sufficiently defined by necessary conditions definition status| or 900000000000074008 | Not sufficiently defined by necessary conditions definition status| . Since July 2019 the information provided by this value is primarily informative and has little practical impact on processing. It indicates whether the necessary conditions defined in the relationships file provide a sufficient definition of the concept. However, the primary representation of the concept definition now uses OWL axioms. These are used to classify the terminology and generate the relationships that represent the inferred definition and to set the definitionStatusId. The change to the OWL axiom is significant and the change to the definitionStatusId is a consequence of that change.
Concept identifiers and terms stored in patient records represent the data as entered and subsequent terminology updates should not result in changes to those original records. This does not preclude additions that reflect the effect of terminology updates on a specific record. However, these additions should be distinct from the original record entries. National and local policies and approaches to this issue may vary depending on legal constraints, clinical guidelines and audit capabilities of EHR systems.
It is possible that a record containing a concept from the new version (V2) might have been received from another EHR instance that was upgraded to V2 earlier. In this case, the receiving system would not include this concept in reports it was upgraded to V2.
In future it may also be possible to include inactive concepts by using the SNOMED Query Language. This query language is being developed to extend the capabilities of expression constraints and is may enable inclusion of inactive concepts that have historical associations with specific active concepts.


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