Transformation Level 1

Terminology servers at Level 1 will accept any expressions represented in valid classifiable form, as in Level 0. Additionally, some expressions that are not already in classifiable form will also be accepted. These will mainly be syntactically compliant expressions that are not MRCM compliant, but which the server can unambiguously transform to derived expressions that are MRCM compliant, using predefined automated transforms.

Loose Attributes

A loose attribute is any attribute within a CTU expression that is not in an attribute group AND the MRCM specifies:

  • that it should be grouped, or

  • that it is in the wrong domain

Scope of Transformations

Level 1 transformations of CTU expressions may apply to expressions meeting the following criteria.

  • Transformations can only apply where there is no definition status

  • There must be only one focus concept

  • Level 1 transformations can only apply to loose attributes (as defined above)

  • When the expression contains a mixture of loose attributes and attribute groups, the attribute groups are effectively treated as for Level 1, so no transformation of these are attempted

Transformation Process

Expression syntax, concepts being active and MRCM attribute-range validation should be applied before the transformation step. Implementations should fail fast if these are not met and not attempt transformation. This simplifies the preconditions for specific transformations.

The process of applying the transformations is iterative. This includes: collecting the set of remaining loose attributes, then applying the next transformation, and repeating until each transformation has been applied once. When each specific transformation is applied it should be greedy and transform all the loose attributes that meet the conditions of that transformation.

The list of transformations must be applied in a specific order; to ensure that the same classifiable expression is reached every time by all implementations.

Transformations

The allowed patterns can be summarized as follows:

  1. Refining Existing Attribute

  2. Adding a Self-grouped Attribute

  3. Adding Severity to Clinical Findings

  4. Lateralizing Clinical Findings

  5. Lateralizing Procedures

  6. Adding Context to Clinical Findings

  7. Adding Context to Procedures

The following sections elaborate on the preconditions and behaviour of each pattern.

Refining Existing Attribute

In this case, the terminology server will accept attributes-value pairs with the following characteristics:

  • The attribute is already present in the NNF of the focus concept

  • The attribute value stated in the expression is a subtype of the attribute value of the focus concept

Important Notes

  • If no groups are stated in the CTU expression (i.e. attributes are declared as loose attributes), the terminology server will accept attribute-value pairs correctly belonging to role groups of the focus concept as follows:

    • The terminology server will accept attribute-value pairs that refine one or more of the attribute-value pairs of the focus concept, i.e.

      • The attribute type should be the same as, or a subtype of, an attribute that already exists in the NNF of the focus concept, for which

        • The attribute value may be the same as, or a subtype of, the existing attribute value

    • The terminology server will reject attribute-values, if this is a supertype of the attribute value used in the definition of the focus concept

  • If groups are stated in the CTU expression

    • The terminology server will accept groups that refine an existing role group of the concept, i.e. the group stated in the CTU should represent a subtype of the role group of the focus concept

The following table provides examples of CTU expressions candidate to this pattern, and their evaluation at level 1.

CTU expression
Evaluation
Classifiable Form

Adding a Self-grouped Attribute

Transformation Preconditions

This transformation will be applied to all loose attributes that meet the following conditions:

  • The attribute applies to the MRCM domain of the focus concept (see table below)

  • Only one instance of the attribute is stated in the CTU expression

    • Although the MRCM allows multiple instances, this transformation condition aims to avoid misinterpretation of the intended meaning

  • Either:

    • The attribute type is not already used in the necessary normal form of the focus concept

      • For example, if the focus concept already has a |Due to| attribute in the NNF then an expression including |Due to| would not be accepted

    • The attribute type is already used in the necessary normal form of the focus concept and the value is equal to or a subtype of the existing value

      • I.e. it represents a refinement

The following table shows the self-grouped attributes and the domain they apply to

Clinical finding Attributes
Procedure Attributes

before

priority

during

has focus

after

due to

clinical course

temporally related to

associated with

Please refer to the Editorial Guide for instructions on the use and the implied meaning of these attributes:

  • Clinical Finding Defining Attributes

  • Procedure Defining Attributes

As part of the expression transformation process, the terminology server will place the attributes in groups on their own, as shown in the examples below.

Examples of CTU expressions candidate to this pattern, and their evaluation at level 1.

Adding Severity to Clinical Findings

At level 1, the terminology server will accept CTU expressions matching the following pattern:

[[+ (< 404684003 |Clinical finding| MINUS << 162465004 |Symptom severity| ) @finding]]:
246112005 |Severity| = [[+ (<< 272141005 |Severities (qualifier value)| ) @severity]]

This means that CTU expressions that includes the severity attribute will be accepted if the following criteria are met:

As part of the transformation process, the terminology server will place the attribute in a group on its own, similar to the self-grouped attributes.

Examples of CTU expressions candidates to this pattern, and their evaluation at level 1.

Lateralizing Clinical Findings

The terminology server will accept CTU expressions matching the following pattern:

[[+ (< 404684003 |Clinical finding| ) @finding]]:
272741003 |Laterality| = [[+ (< 182353008 |Side| ) @side]]

The transformation of expressions following this pattern will include the following steps:

  1. Copy the defining properties and role groups of the focus concept (as present in the NNF) to the classifiable form expression

  2. Replace the value of the |Finding site| attribute with a nested expression:

From:

@finding.363698007 |Finding site| = @bodySite

To:

363698007 |Finding site| = (@bodySite: |Laterality| = [[+ @side]] )

Important Notes

The terminology server will only accept expressions complying to this pattern if the focus concept of the CTU expression has the following characteristics:

The focus concept

  • includes only one role group with a |Finding site| attribute OR

  • includes two or more role groups with a |Finding site| attribute WHERE

    • the value of the finding site attribute in each role group is the same concept

  • includes no attributes with values that are already lateralized anatomical structures (ie values whose own definitions already include a value for the 272741003|Laterality| attribute

The value of the finding site attribute is a member of the 723264001 | Lateralizable body structure reference set|

  • being a member of this refset means that the associated body structure is lateralizable, and does not already state a laterality other than 182353008 |Side|

Transformation of bilateral findings

When applying the concept 51440002 | Right and left| as the value for the 272741003 | Laterality| attribute, the transformation should be done in accordance with the modeling applied to the content in the International Edition of SNOMED CT.

This means that the transformation steps described above should be applied twice; one for each lateral half, as illustrated in the example below.

CTU Expression
301354004 |Pain of ear| : 272741003 |Laterality| = 51440002 |Right and left|
Classifiable Form Expression
=== 301354004 |Pain of ear| :
{ 363698007 |Finding site| = ( 117590005 |Ear structure| : |Laterality| = 7771000 |Left| )},
{ 363698007 |Finding site| = ( 117590005 |Ear structure| : |Laterality| = 24028007 |Right| )

Examples

Lateralizing Procedures

The terminology server will accept CTU expressions matching the following pattern:

[[+ (< 71388002 |Procedure| ) @procedure]]:
272741003 |Laterality| = [[+ (< 182353008 |Side| ) @side]]

The transformation of expressions following this pattern will include the following steps:

  1. Copy the defining properties and role groups of the focus concept (as present in the NNF) to the classifiable form expression

  2. Replace the value of the |Procedure site| attribute (or any of its subtypes / @siteAttribute) with a nested expression:

From:

@siteAttribute = @bodySite

To:

@siteAttribute = (@bodySite: |Laterality| = [[+ @side]] )

Transformation of bilateral procedures

When applying the concept 51440002 | Right and left| as the value for the 272741003 | Laterality| attribute, the transformation should be done in accordance with the modeling applied to the content in the International Edition of SNOMED CT.

This means that the transformation steps described above should be applied twice; one for each lateral half, as illustrated in the example below.

CTU Expression
| 52734007 |Total replacement of hip| : 272741003 |Laterality| = 51440002 |Right and left| |
Classifiable Form Expression
=== 52734007 |Total replacement of hip| :
{ 363698007 |Finding site| = ( 117590005 |Ear structure| : |Laterality| = 7771000 |Left| )},
{ 363698007 |Finding site| = ( 117590005 |Ear structure| : |Laterality| = 24028007 |Right| )}

Examples of CTU expressions and their evaluation at level 1.

CTU Expression
Evaluation
Classifiable Form

Adding Context to Clinical Findings

At level 1, the terminology server will accept CTU expressions matching the following pattern:

[[<< 404684003 |Clinical finding| @finding]]:
[[0..1]] 408729009 |Finding context| = [[+id(<< 410514004 |Finding context value| )@context]],
[[0..1]] 408731000 |Temporal context| = [[+id(<< 410510008 |Temporal context value| )@time]],
[[0..1]] 408732007 |Subject relationship context| = [[+id(<< 125676002 |Person| )@person]]

This pattern allows attributes applicable to the 413350009 | Finding with explicit context (situation)| domain to be used to add contextual information to clinical finding concepts.

The generated classifiable form must be based on the following expression with 413350009 | Finding with explicit context (situation)| as the focus concept and the following default attributes and values unless otherwise specified by the CTU. The value of the Associated finding attribute will be replaced by the focus concept of the CF expression.

=== 413350009 |Finding with explicit context| :
{ 246090004 |Associated finding| = 404684003 |Clinical finding| ,
408729009 |Finding context| = 410515003 |Known present| ,
408732007 |Subject relationship context| = 410604004 |Subject of record| ,
408731000 |Temporal context| = 410512000 |Current or specified time| }

Examples of CTU expressions and their evaluation at level 1.

Adding Context to Procedures

At level 1, the terminology server will accept CTU expressions matching the following pattern:

[[<< 71388002 |Procedure| @procedure]]:
[[0..1]] 408730004 |Procedure context| = [[+id(<< 288532009 |Context values for actions| ))@context]],
[[0..1]] 408731000 |Temporal context| = [[+id(<< 410510008 |Temporal context value| )@time]],
[[0..1]] 408732007 |Subject relationship context| = [[+id(<< 125676002 |Person| )@person]]

This pattern allows attributes applicable to the 29125009 | Procedure with explicit context (situation)| domain to be used to add contextual information to procedures.

The generated classifiable form must be based on the following expression with 29125009 | Procedure with explicit context (situation)| as the focus concept and the following default attributes and values, unless otherwise specified by the CTU. The value of the Associated procedure attribute will be replaced by the focus concept of the CF expression.

=== 129125009 |Procedure with explicit context| :
{ 363589002 |Associated procedure| = 71388002 |Procedure| ,
408730004 |Procedure context| = 385658003 |Done| ,
408732007 |Subject relationship context| = 410604004 |Subject of record|
408731000 |Temporal context| = 410512000 |Current or specified time| }

Examples of CTU expressions and their evaluation at level 1

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