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Footnote Macro

Diagram uses notation from Diagramming Guideline.

Caption label
CapIdexample-of-subsumption
CapTypeFigure
Example of subsumption

This also means that if a patient has a

Concept
t54441004 |Fracture of shaft of femur|
, then it is implied (i.e. it is also true) that they have a
Concept
t71620000 |Fracture of femur|
. We can use this principal to aggregate health records that have been encoded with SNOMED CT. By selecting any code that is a subtype of
Concept
t71620000 |Fracture of femur|
, we are selecting all the codes that imply that
Concept
t71620000 |Fracture of femur|
ShowFormatinline
is true (given the appropriate context).

Anchor
transitivity
transitivity
When testing for subsumption, we must also consider the transitivity of the
Concept
t116680003 |is a|
ShowFormatinline
relationship. For example, the diagram below indicates that
Concept
t426656000 |Severe persistent asthma|
ShowFormatinline
is a subtype of
Concept
t370221004 |Severe asthma|
ShowFormatinline
which is a subtype of
Concept
t195967001 |Asthma|
. Therefore
Concept
t426656000 |Severe persistent asthma|
ShowFormatinline
is also a subtype of
Concept
t195967001 |Asthma|
.

Caption label
CapIdexample-of-subsumption-and-transitivity
CapTypeFigure
Example of subsumption and transitivity

As previously suggested in the section  1.4. SNOMED CT Features, the hierarchical relationships of SNOMED CT can be leveraged to enable clinical decision support. More specifically, we can apply

Gloss
PreSpacefalse
tsubsumption testing
GlosTermSubsumption test
to make additional determinations. For additional information on subsumption, please refer to  6.2 Subsumption in  Data Analytics with SNOMED CT .

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The diagram below shows a simple CDS rule based on the IF-condition-THEN-action pattern. This rule uses the descendant or self operator (<<) from the  Expression Constraint Language - Specification and Guide to check if the diagnosis is in the set of concepts that includes

Concept
t195967001 |Asthma|
ShowFormatinline
and all of its subtypes.

Caption label
CapIdcds-rule-defined-using-subsumption
CapTypeFigure
CDS rule defined using subsumption

Execution of Rule

When executing this rule, the inference engine tests if the given diagnosis is subsumed by the concept

Concept
t195967001 |Asthma|
. This subsumption testing can be performed using a range of approaches, including using a 7.5.2 Transitive closure implementation. A transitive closure table facilitates rapid facilitates  rapid testing of all possible
Concept
t116680003 |is a|
ShowFormatinline
relationships, and provides a very effective way of testing concept subsumption in relational databases.

The diagram below illustrates the process followed by the inference engine in executing the CDS condition in the above rule, when the clinician selects a diagnosis of

Concept
t426979002 |Mild persistent asthma|
. The inference engine checks if this concept is a subtype of
Concept
t195967001 |Asthma|
, and determines that it is. As a result, the condition evaluates to true, and the action is triggered.

Caption label
CapIdthe-inference-engine-checks-if-the-diagnosis-entered-is-a-subtype-of-asthma-
CapTypeFigure
The inference engine checks if the diagnosis entered is a subtype of |Asthma|


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