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© International Health Terminology Standards Development Organisation 2012. All rights reserved.
SNOMED CT® was originally created by the College of American Pathologists.
The International Release of SNOMED CT® is distributed by the International Health Terminology Standards Development Organisation (IHTSDO), and is subject to the IHTSDO's SNOMED CT® Affiliate Licence. Details of the SNOMED CT® Affiliate Licence may be found at http://www.ihtsdo.org/our-standards/licensing/.
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<ac:structured-macro ac:name="anchor" ac:schema-version="1" ac:macro-id="f5203417-0842-4193-893a-0a81bc1ddf5b"><ac:parameter ac:name="">TableOfContents</ac:parameter></ac:structured-macro><span style="color: #1f2b7c">Table of Contents</span>
<span style="color: #1f2b7c">1 Glossary</span>
1.1 Domain Terms
<span style="color: #1f2b7c">2 Introduction</span>
2.1 Purpose
2.2 Audience and stakeholder domain
2.2.1 Input from stakeholders
2.2.2 Degree of consensus on the statement of problem
<span style="color: #1f2b7c">3 Statement of the problem or need</span>
3.1 Summary of problem or need, as reported
3.2 Summary of requested solution
3.3 Statement of problem as understood
3.4 Detailed analysis of reported problem, including background
3.4.1 Background
3.4.2 Detailed analysis of the problem
3.4.3 Distinction between clinical finding, situation with explicit context, and observable entity content
3.5 Subsidiary and interrelated problems
3.6 Summary of discussion and preliminary considerations for solutions
<span style="color: #1f2b7c">4 Risks / Benefits</span>
4.1 Risks of not addressing the problem
4.2 Risks of addressing the problem
4.3 Benefits of addressing the problem
<span style="color: #1f2b7c">5 Requirements: criteria for success and completion</span>
5.1 Criteria for success/completion
5.2 Strategic and/or specific operational use cases
5.2.1 Use case 1
5.2.2 Use case 2
<span style="color: #1f2b7c">6 Solution Development</span>
6.1 Initial Design
6.1.1 Outline of initial design
6.1.2 Significant design or implementation decisions / compromises
6.1.3 Evaluation of Design
<span style="color: #1f2b7c">7 Recommendation</span>
7.1.1 Detailed design final specification
<span style="color: #1f2b7c">8 Quality program criteria</span>
8.1 Quality metrics
8.1.1 Quality metric 1
8.1.2 Quality metric 2
8.1.3 Quality metric 3
8.1.4 Quality metric 4
<span style="color: #1f2b7c">9 Project Resource Estimates</span>
9.1 Projection of remaining overall project resource requirements
9.1.1 Expected project resource requirement category
9.1.2 Expected project impact and benefit
<span style="color: #1f2b7c">10 Appendices</span>
10.1 Appendix A – IHTSDO SIRS Requests as of September 2015
10.2 Appendix B – Presence of <device> Concepts
10.3 Appendix C – Presence of <surgically created anatomical structure> Concepts
10.4 Appendix D – Proposed Observable Entity Concept Model for Observation Results
10.5 Appendix E – References

Glossary

Domain Terms

Introduction

Purpose

The purpose of this project is to consider content and modelling issues related to existing and newly requested SNOMED CT concepts following the pattern "Presence of X."
This document combines the documentation of the Inception and Elaboration Phases. The Inception Phase focuses on understanding the problem and its scope, identifying stakeholders and their requirements, and identifying risks. The purpose of the Elaboration Phase is to develop, document and test one (or more) possible technical solutions, and to reach a recommendation and provide a detailed specification of a preferred solution to be taken forward to the construction phase.

Audience and stakeholder domain

The audience for this document includes all standards terminology leaders, implementers and users, but it is especially targeted at the community of SNOMED CT authors that may be requested to implement the recommended specification. The content of this document may also be relevant to request submitters from National Release Centres as well as those clinicians or implementers who utilize SNOMED CT for recording patient data within clinical information systems.

Input from stakeholders

Many requests for SNOMED CT concepts following the pattern, "Presence of X" (or very similar patterns), have been received. As of September 2015, there are at least 39 requests for content that follow this or a similar pattern within the IHTSDO SNOMED CT International Request Submission (SIRS) system. While this may not seem to be a large number, these types of requests continue to be received and are related to larger content issues within SNOMED CT. For these reasons, it would be beneficial to evaluate this issue for the SNOMED CT authors who address these requests as well as and to seek input from them regarding any potential solution, particularly in relation to any difficulties they have been experiencing to date with this type of content.
Feedback received to date includes a brief discussion with a Consultant Terminologist who pointed to a presentation on the Observables and Investigation Procedures Redesign work which addresses Presence/Absence of X content (artf6283).  The presentation proposed an observables conformant approach to representing the presence/absence of observation results, including surgically created structures, therefore directly relevant to this current project.
Further discussion with IHTSDO editors regarding the approach suggested as an interim measure to scope the project to management of requests within the current concept model and the production of terming guidance to standardize this was well received. Though they did not see the detailed terming/modelling guidance presented in this paper.  They also agreed it was important that the project ensured any recommended disposition would carefully consider the larger associated projects and not have an adverse impact upon them. 

Degree of consensus on the statement of problem

The degree of consensus on the statement of problem is currently unknown because this content issue is related to multiple large-scale projects currently under development within SNOMED CT. The degree of consensus regarding the problem as well as relevant solutions will depend on the related projects. This document aims to provide background information related to this content project, define the problem, outline specific modelling issues, identify associated large scale projects, and provide solutions which can be implemented in the near future while awaiting the outcomes and dependencies of the larger content projects.

Statement of the problem or need

Summary of problem or need, as reported

As stated in the IHTSDO CollabNet tracker description for artf222786 : Concept model: Presence of X (situation) - presence of X (finding):
https://csfe.aceworkspace.net/sf/go/artf222786?qkSrchApp=objectId
"Requests for "Presence of X (situation)" where X is either an implanted device (e.g. Presence of shoulder joint replacement (situation)) or else a surgically created anatomical structure (e.g. Presence of urostomy (situation))
The 'accepted' working approach dictates that the presence of 'normal' structures or functions are findings, while the outright statement of presence of abnormal structures or findings (as opposed to just naming them) would be treated as situations, with a context of "known present." Laboratory findings when 'present' are also findings. Though the rationale by which a "Clinical finding present" is a situation while "Laboratory findings present" is a finding is based on an assumption that the laboratory findings name things not normally present (e.g. abnormal cells), which isn't universally the case (some name things normally present, or in quantities/ranges that are normal)."

Summary of requested solution

As stated on the IHTSDO CollabNet tracker for artf222786:
"Solutions should take account of the newer definition of situation (period of the subject's life in which a condition is present), and condition (a structure, process or disposition); and separately take account of the newer definition of observation results, into which many laboratory findings will fit."

Statement of problem as understood

Requests for content following the patterns "Presence of X" and "X present" continue to be received and require modelling guidance. While there has been a working modelling approach to address this content, existing content does not follow the approach consistently. In addition, new requests for specific types of "Presence of X" and "X present" content related to devices and surgically created anatomical structures present modelling challenges such that the working approach cannot be easily implemented. Furthermore, there are large-scale content projects currently under development within SNOMED CT that will likely impact how this content will be addressed once those projects are completed. The expectation is that usable editorial guidance will be produced for "Presence of X" content in relation to devices and surgically created anatomical structures. This guidance would result in consistent content development in these areas, also meeting the needs of the current requesters pending the outcome of larger associated content projects.

Detailed analysis of reported problem, including background

The following topics will be addressed in this section:

• Review of background information: Existing SNOMED CT editorial policy, SIRS requests, and existing content following the patterns "Presence of X" and "X present" (Section 3.4.1)
• Review of specific content areas that present challenges for modelling (Section 3.4.2)
• Review of larger content projects currently under development within SNOMED CT and their relevance to (and dependency for) this artefact (Section 3.4.3)

Background

Existing Editorial Policy
In general, concepts following the patterns "Presence of X" and "X present" may be used to represent assertions of context that a condition exists or is occurring in a patient at this time. As stated in the SNOMED CT Editorial Guide Section 6.4.3.2 (January 2015):
"The default context for a clinical finding code implies that the finding has actually occurred (vs. being absent), that it applies to the subject of the record (the patient), and that it is occurring currently or occurred at a past time that is given by a date - time record linked to the code.
The FINDING CONTEXT attribute [used to model concepts within the situation explicit context hierarchy] is used to represent a situation in which a Clinical finding is known or unknown, and if known, whether it is present, absent, or uncertain (possible); and also to express the meaning that the finding is not actual but instead an anticipated or possible future finding."
Currently this content can be found in multiple hierarchies in SNOMED CT – as clinical finding, situation with explicit context, or observable entity concepts – indicating that this content has been modelled inconsistently over time. With respect to specific modelling guidelines, according to artf222786, the working approach for modelling "Presence of X" and "X present" content has been to model "Presence of <normal structures or functions>" content as clinical findings and to model "Presence of <abnormal structures or findings>" as situations with explicit context. However, as will be seen, this guidance has not been uniformly implemented.
IHTSDO SIRS Requests
Numerous new requests for "Presence of X" and "X present" content continue to be received. As of September 2015, there are 39 requests in the IHTSDO SNOMED CT International Request Submission (SIRS) system associated with artf222786. The majority of these requests are for content following the patterns "Presence of <device>" and "Presence of <surgically created anatomical structure>." In addition, there may be over 25 additional related requests that have not been specifically associated with this artefact, but may still be relevant. These requests are related to laboratory and other test results as well as content following the pattern "On examination – X." A few examples of these SIRS requests are shown below, but please see Appendix A for a complete list.

Survey of Existing Content
A search of the July 2015 International Release yielded a fair number of existing concepts with "presence" or "present" in fully specified names (FSNs) and descriptions across the clinical finding, situation with explicit context, and observable entity hierarchies. The table below lists the number of related concepts found in each hierarchy; the majority of the content is located within the clinical finding hierarchy and is related to laboratory content. The list of concepts for each set of results can be found in a spreadsheet associated with this project: artf222786_PresenceOfX_Concepts_Combined_Inception_Elaboration_Phase_v0.1.xlsx

Detailed analysis of the problem

This section will provide a more detailed review of specific content issues and challenges related to this artefact.

Existing content modelling inconsistencies

While some existing content does follow the working modelling approach, there are a number of instances of inconsistencies. For example, the current working approach recommends that content following the pattern "Presence of <abnormal structures or findings>" should be modelled as situation with explicit context concepts, however, the concepts listed below are found in the clinical finding hierarchy:

• 302111002 | Ileostomy present (finding)
• 307699005 | Nystagmus present (finding)
• 162236007 | Weakness present (finding)
• 274825006 | Ptosis present (finding)
• 301920009 | Enophthalmos present (finding)
• 302113004 | Urostomy present (finding)
• 164274003 | On examination - stridor present (finding)

In addition, some content can also be found in the observable entity hierarchy. While these concepts were likely created to encode data elements within clinical questionnaires or forms, when these types of concepts are encountered in search results, their use case may not be immediately apparent to implementers:

• 284089007 | Presence of orthopedic joint implant (observable entity)
• 428395000 | Medical identification bracelet present (observable entity)
• 278652005 | Tooth presence (observable entity)

Presence of device / Device present / Device in situ content

"Presence of <device>" and "<Device> present" concepts are likely used to assert that a device is present in the subject of record. Most of this content is located in the 397578001 | Device in situ (finding) hierarchy. Based on the modelling and descriptions of existing concepts, the terms "presence of device" and "device present" appear to be synonymous with "device in situ" in SNOMED CT. As of the July 2015 International Release, there are 58 concepts in this sub-hierarchy (and there may be other existing concepts that should be in this sub-hierarchy, but are not). In addition, there are multiple new requests for similar concepts in SIRS. (Please see Appendix A for SIRS requests and Appendix B for a list of existing Device in situ (finding) concepts.)
Since the presence of a device would not be considered a normal finding or structure, according to existing guidance, it is expected that this content would be in the situation with explicit context hierarchy. However, as shown in the table below, this content has been added in the clinical finding hierarchy, specifically as subtypes of 397578001 | Device in situ (finding). This is likely because current editorial policy does not allow <physical object> concepts as values for the ASSOCIATED FINDING attribute in the situations with explicit context hierarchy concept model. Therefore, modelling this content in the situations hierarchy presents a significant challenge. Modelling recommendations for this content will be addressed in Section 6 of this document.

Presence of surgically created anatomical structure content

In a similar way to devices, surgically created anatomical structures, which are acquired body structures created as a result of an operative procedure, would also not be considered "normal findings."
Within SNOMED CT, surgically created anatomical structures are represented as morphological abnormalities:

• There are two sub-hierarchies with concepts representing this type of content: 245849007 | Post-surgical anatomy (morphologic abnormality) and 43526002 | Operative site (morphologic abnormality).
• For example 245857005 | Stoma (morphologic abnormality) and its subtypes are used to model the FINDING SITE and DIRECT MORPHOLOGY for clinical finding and procedures concepts respectively.

Based on existing guidance, "Presence of <surgically created anatomical structure>" would expect to be represented as situation with explicit context concepts.  However, this content is also located within the clinical finding hierarchy. As shown in the table below, there are several existing concepts of this nature. In addition, there are several requests in SIRS for this type of concept and all have been requested as clinical findings.  (Please see Appendix A for SIRS requests and Appendix C for a list of existing concepts.) The current situation with explicit context concept model does not allow <body structure> concepts as values for the ASSOCIATED FINDING attribute. Therefore, like the pattern "Presence of <device>," this content also presents significant modelling challenges, and recommendations will be addressed in Section 6 of this document.

Laboratory finding contents

Existing subtypes of 441742003 | Evaluation finding (finding) include over 200 concepts following the patterns "Presence of X" and "X present." Although there are instances of something normally present e.g., 250441008 | Epithelial cells present (finding), this is not always the case e.g., 250439007 | Pus cells present (finding). Some laboratory findings are expressed in the format we would expect of an observable entity concept e.g. 365707003 | Finding of presence of viral antigen (finding).  These are grouper concepts and although some have subtypes of "X present (finding)"; others have no subtypes so do not appear to stand on their own merit as findings.  In the example given, the concept is modelled with the attribute INTERPRETS with the value 122433001 | Viral antigen assay (procedure).  Concepts following the pattern, "Finding of presence of X," without subtypes seem ambiguous.  Some of this content originates from United Kingdom National Health Service (UK NHS) Read codes, but within the Read codes, the map from X76zR | Presence of viral antigen (this is a synonym of 365707003 | Finding of presence of viral antigen (finding)) is to 122433001 | Viral antigen assay (procedure), supporting the suggestion that the concept is redundant and ambiguous.
Laboratory finding content was an exception to the working modelling approach and some content representing abnormal test results was historically added to the clinical finding hierarchy. However, in 2013, the IHTSDO entered a cooperative agreement with the Regenstrief Institute, the owners of the Logical Observation Identifiers Names and Codes (LOINC) standardized terminology. As part of this agreement, the addition of new pre-coordinated laboratory content will be significantly restricted within SNOMED CT. Existing content is now being addressed as part of artf6144 : Evaluation findings, evaluation procedures and artf6283 : Observables and investigation procedures redesign. For these reasons, the domain of laboratory content will be considered out of scope for the purposes of this project.

Absence of X / X absent / X not present content

Content representing the patterns "Absence of X," "X absent," and "X not present" are similar in nature to "Presence of X" and "X present" as these patterns are explicit assertions of context. A search of the July 2015 International Release yielded a fair number of existing concepts with these patterns in fully specified names (FSNs) and descriptions across the clinical finding and situation with explicit context hierarchies. The table below lists the number of concepts by hierarchy there are also a few requests within SIRS that can be found in Appendix A. Of note, there are additional negation patterns such as "No X" and "Non-X" which are difficult to detect and quantify due to naming inconsistencies. The list of concepts for each set of results below can be found in a spreadsheet associated with this project:
artf222786_PresenceOfX_Concepts_Combined_Inception_Elaboration_Phase_v0.1.xlsx

The meaning of these concepts depends conceptually on negation; therefore, the content would be expected to be in the situation with explicit context hierarchy. However, as shown below, there is inconsistent representation of these concepts such that some concepts follow the format of "<normal structure> absent" represented as a clinical finding and an "<abnormal structure> absent" represented as a situation, e.g.:

• 37280007 | Absent reflex (finding)
• 162363005 | No ear discharge (situation)
• 163010002 | On examination - pulse absent (finding)
• 164016004 | On examination - ptosis absent (situation)

In addition, there are some inconsistencies in that 274824005 | Ptosis absent (finding) could be a duplicate to 164016004 | On examination - ptosis absent (situation) and confusing when presented with both to clinicians. There are also some inconsistencies in modelling: 234948008 | Tooth absent (finding) is modelled with the attribute-value pair HAS INTERPRETATION 2667000 | Absent, whereas 300309008 | Appendix absent (finding) is not. The representation and classification of content representing negation presents significant challenges within SNOMED CT, and has been the subject of much discussion. This content is currently actively under review as part of artf7618 : Negation and Context, and therefore content pertaining to negation will be considered out of scope for the purposes of this project.

"On examination" content

As of the July 2015 International Release, there are over 1900 "On examination – X (finding)" concepts and over 120 "On examination – X (situation)" concepts. The list of concepts for each set of results can be found in a spreadsheet associated with this project: artf222786_PresenceOfX_Concepts_Combined_Inception_Elaboration_Phase_v0.1.xlsx
These concepts represent a clinical finding "observed" or "not observed" on examination, and therefore, could be construed as an assertion of context – presence or absence – of that clinical finding. In some cases "present" or "absent" is explicitly stated in the FSN, while in other cases it is not. In addition, there are many instances of concepts representing the presence of abnormal findings, which would expect to be found in the situations hierarchy, but are instead are found in the clinical findings hierarchy:

In addition, there are instances of sets of concepts that are very similar to each other (if not duplicates), which has the potential to cause confusion for implementers:

The "On examination" content in SNOMED CT originates from the NHS Read Codes and any changes to this content are likely to have significant impact on implementation within the NHS. This content has already been designated as a separate IHTSDO content project under artf6321 : On examination – semantics; therefore this content will be considered out of scope for the purposes of this project.

Distinction between clinical finding, situation with explicit context, and observable entity content

As the above sections demonstrate, content following the patterns "Presence of X" and "X present" can be found in multiple hierarchies in SNOMED CT. Furthermore, the content within these hierarchies is represented inconsistently and may in some cases be redundant. Addressing existing content and new requests will ultimately depend on clear definitions and distinctions between the clinical finding/disorder, situation with explicit context, event, and observable entity hierarchies to ensure that content is modelled in a consistent and reproducible manner. Therefore, addressing "Presence of X" content is significantly dependent upon the outcomes of several related artefacts, including:

• artf6167 : Situation hierarchy refinement
• artf6283 : Observables and investigation procedures redesign
• artf231800 : Refining meaning in clinical findings, including situation, disorder, observation result.

Section 6.1.1 of the IHTSDO Editorial Guide also refers to the challenges of this distinction:
"More precise and reproducible definitions of clinical findings, and the precise boundaries between findings and events, between findings and observables, between findings and situations, and the distinction between finding and disorder, remain ongoing challenges at the margins."
Clearly defining and distinguishing these hierarchies is also a subject of active discussion within the artf6209 : Event, condition, episode working group. In addition, the Inception-Elaboration phase document associated with artf231800 states that existing clinical finding/disorder, situation with explicit context, event, and observable entity hierarchies do not sufficiently distinguish between several distinct categories of content as shown below:

With respect to these categories, "Presence of X" content could be divided into two general types of content:

1. Laboratory content: Existing laboratory content will likely fall into the observation result category, though because of the cooperative agreement between the IHTSDO and Regenstrief Institute, the addition of new laboratory content will likely be significantly restricted.

1. Non-laboratory content: Addressing non-laboratory "Presence of X" content (e.g., the other content areas described in Section 3.4) requires that the categories listed above be further defined and implemented within SNOMED CT. However, there is an important comment made in the artf231800 Inception-Elaboration phase document, which references "Presence of X" content. Specifically, there is a question as to whether this content should even be included as pre-coordinated content within SNOMED CT:

"Most "situation" codes clearly imply that they must be an information entity about a clinical phase; however, when it comes to "disease present (situation)" there is a decision needed. The question is about whether it is useful in any way to have two codes, one for the situation and one for the disorder. For example, "Chronic disease present (situation)" represents an information entity – an assertion that a chronic disease is present, and "Chronic disease (disorder)" represents the life phase in which a chronic disease is borne by the patient. There may not be a need for two codes, but two exist, and there are two different meanings that can be discerned. Some users expect that there should be either a complete prohibition of precoordination of any situation codes of this type; or else they assume it implies a commitment to complete expansion to precoordinate all possible situation codes of this type… Expectations that SNOMED CT must require complete prohibition, or that it must allow complete expansion, are both unrealistic…"
Based on this information, how the "Presence of X" pattern is addressed going forward will depend on the outcome of content decisions made at a higher level within SNOMED CT. Please see the Inception-Elaboration phase document associated with artf231800 for further details.

Subsidiary and interrelated problems

The following artefacts are associated with artf222786 : Concept model: Presence of X (situation) - presence of X (finding) on the IHTSDO CollabNet content tracker:

• artf6167 : Situation hierarchy refinement
• artf6311 : Adopt systematic naming for FSNs with "on examination", "X present", "X absent", etc
• artf222785 : Concept model: Presence
• artf222838 : Concept model: "X presence known absent" or "X absence known present"

As stated in Section 3.4.3, the Situation hierarchy refinement project is a significant dependency for this project. The Situation hierarchy refinement project is under active review; however, this "Presence of X" project (artf222786) as well as all of the projects listed above depend on content decisions to be determined at a higher level. More specifically, each of the artefacts listed above will depend on 1) whether pre-coordinated "Presence of X" content will continue to be allowed in SNOMED CT, and 2) if allowed, how this content will be able to be integrated within the top-level categories of clinical condition, clinical life phase, and information entity as defined in artf231800 : Refining meaning in clinical findings, including situation, disorder, observation result.

Summary of discussion and preliminary considerations for solutions

This section has highlighted content issues related to the "Presence of X" and "X present" pattern:

• New requests for this content continue to be received, indicating that this content is needed for user implementation. Some requests have been outstanding since December 2013, suggesting that an interim solution would be valuable to address immediate user needs.
• There remain questions as to whether this content should be pre-coordinated within SNOMED CT, and if so, how it should be modelled.
• A working modelling approach has been in place, though some existing content is modelled inconsistently. "Presence of X" and "X present" content can be found in multiple hierarchies and in a few cases may be redundant.
• A review of "Presence of X" content in the July 2015 International Release yielded subsets of content which are being addressed in other content projects and therefore are considered out of scope for the purposes of this project:
  • Laboratory finding content – addressed in artf6144 : Evaluation findings, evaluation procedures and artf6283 : Observables and investigation procedures redesign
  • "On examination" content – addressed in artf6321 : On examination – semantics
  • Absence of X / X absent / X not present content – addressed in artf7618 : Negation and Context
• Ensuring that existing "Presence of X" and "X present" content and new requests are modelled consistently will ultimately depend on changes under consideration for the clinical finding/disorder, situation with explicit context, event, and observable entity hierarchies. This includes defining and implementing the newer content categories: clinical condition, clinical life phase, and information entity (which includes observation results). Therefore, addressing "Presence of X" content is significantly dependent upon the outcomes of several related artefacts, including:
  • artf6167 : Situation hierarchy refinement
  • artf6283 : Observables and investigation procedures redesign
  • artf231800 : Refining meaning in clinical findings, including situation, disorder, observation result

The original CollabNet description of artf222786 references two specific types of "Presence of X" content: "Presence of <device>" and "Presence of <surgically created anatomical structure>." In addition, these two subsets of content comprise the vast majority of new SIRS requests pertaining to this artefact. Upon further discussion with the IHTSDO Consultant Terminologist Program (CTP) leader and 2015 CTP cohort, it was decided that "Presence of <device>" and "Presence of <surgically created anatomical structure>" would be considered the content which is in scope for suggested solutions. The primary objective of the following sections will be to provide modelling recommendations which can be implemented in the near term while awaiting the outcomes of the larger scale projects.

Risks / Benefits

Risks of not addressing the problem

Risks of not addressing the problem include:

• The potential for continued inconsistent modelling of content across multiple hierarchies as well as content duplication, all of which can cause confusion for modellers and implementers.
• Not addressing the problem will cause implementers to use inconsistent terminology when recording patient problem list entries.
• As stated in the Inception-Elaboration phase document associated with artf231800, if the problems are not addressed, "there is a risk of erosion of clinical confidence in SNOMED CT, resulting in lower levels of adoption, lower value to the clinical users, and increased potential for the creation or adoption of alternative or competing terminologies."

Risks of addressing the problem

Risks of addressing the problem include:

• It may be determined that some existing content should be changed or retired, which may cause problems for implementers.
• The outcomes of larger projects are dependencies for this project. Recommendations made for smaller content areas in the near term will likely be impacted by, if not conflict with, future decisions made for the larger projects.
  • Multiple changes over time can cause issues for implementers.
  • Multiple changes can require increased modelling time for terminology authors, however, harmonizing existing and new content in the short term should hopefully assist with making content changes in the future if/when new modelling recommendations are made.
• More detailed review of existing content may result in the discovery of additional problems that have not yet been addressed.

Benefits of addressing the problem

Benefits of addressing the problem include:

• Addressing the problem should result in improved consistency of modeling and harmonization of content, which should in turn result in easier, more accurate, and more consistent concept selection by users for recording patient data.
• Addressing the problem should also increase user confidence that their requests are being addressed in a timely manner.

Requirements: criteria for success and completion

Criteria for success/completion

The criteria for success will be:

• Sufficient guidance given to IHTSDO editors to enable them to author the existing requests for "Presence of <device>" and "Presence of <surgically created anatomical structure>" content with clear scope and definition whilst paying due regard to the larger associated projects. This will result in:
  • Consistent application of a terming pattern for these requests
  • Consistent application of a logic-based modelling pattern to these requests
• Whilst responsive in meeting the current needs of the requesters, consistency of application of the solution suggested here will not adversely impact any of the ongoing project work. Indeed, with consistent application it will be an easier task to identify affected content when required at a later date.

Strategic and/or specific operational use cases

Based on the document, IHTSDO Strategic Directions to 2015, this project meets the following IHTSDO strategic goals:

• IHTSDO Strategic Priority 1: Make it easier to use SNOMED CT for priority use cases.
  • This solution could make it easier to use SNOMED CT in contributing to the improved delivery of care with completeness in problem lists.
  • Facilitating the accurate collection and sharing of clinical and related health information by improving the semantic representation and interoperability of health records.

• IHTSDO Strategic Priority 2: Produce robust terminology standards that are "fit for purpose" for priority use cases
  • Include documentation of the agreed solution to ensure consistent application and maintenance of related content.
  • As noted above in Section 4.1: The Inception-Elaboration phase document associated with artf231800 states if the problems are not addressed, "there is a risk of erosion of clinical confidence in SNOMED CT, resulting in lower levels of adoption, lower value to the clinical users, and increased potential for the creation or adoption of alternative or competing terminologies."

• IHTSDO Strategic Priority 4: Strengthen the responsiveness and clinical governance of SNOMED CT
  • Users are likely to be strongly engaged if IHTSDO are responsive to their needs and although some requests may be held pending completion of associated projects interim solutions should be considered where possible.

Use case 1

Requests for content relating to "Presence of <device>" for use within a problem list.
1A Patient summary / Discharge summary
1B Problem list
2B Continuity of care / Discharge plans

Fit with IHTSDO strategy

Addressing this content with the prosed solutions could make it easier to use SNOMED CT. The proposed terming / modelling patterns should make SNOMED CT query results more consistent and robust. Therefore, these solutions support IHTSDO Strategic Priority 1: Make it easier to use SNOMED CT for priority use cases and IHTSDO Strategic Priority 2: Produce robust terminology standards that are "fit for purpose" for priority use cases.

Use case 2

Requests for content relating to "Presence of <surgically created anatomical structures>" for use within a problem list.
1A Patient summary / Discharge summary
1B Problem list
2B Continuity of care / Discharge plans

Fit with IHTSDO strategy

As above, addressing this content with the prosed solutions could make it easier to use SNOMED CT. The proposed terming / modelling patterns should make SNOMED CT query results more consistent and robust. Therefore, these solutions support IHTSDO Strategic Priority 1: Make it easier to use SNOMED CT for priority use cases and IHTSDO Strategic Priority 2: Produce robust terminology standards that are "fit for purpose" for priority use cases.

Solution Development

Initial Design

Outline of initial design

This section will describe the existing modelling challenges related to "Presence of <device>" and "Presence of <surgically created anatomical structure>" and provide recommended solutions to harmonize this content within SNOMED CT while awaiting the outcomes of larger content project dependencies. The recommended approaches apply to both new SIRS requests as well as existing content and include:

• Suggestions for naming conventions for FSNs and descriptions
• Guidelines for modelling

In addition, this section will provide a brief overview of a potential future solution as proposed by the Observables and Investigation Procedures Redesign project.

Presence of device / Device present / Device in situ content

As previously discussed, based upon the working modelling approach, a concept following the pattern "Presence of <device> (finding)" would actually expect to be found in the situation with explicit context hierarchy and might be modelled as shown below, with an ASSOCIATED FINDING value of Device (physical object) and a FINDING CONTEXT value of Known present (qualifier value):


However, currently, this content is found within the clinical finding hierarchy, specifically in the Device in situ (finding) sub-hierarchy. This is likely because existing editorial policy has prohibited the use of a <physical object> concept as the value for the ASSOCIATED FINDING attribute.
To ensure consistent and accurate representation of "Presence of <device>" content within SNOMED CT, there are a few potential modelling approaches:

1. Consider expanding the allowable values for the ASSOCIATED FINDING attribute to include <physical object> concepts
2. Consider adding a new attribute to the situation with explicit context hierarchy to represent an "Associated <device>"

Each of these modelling approaches are valid, but would require a separate content project to fully evaluate all eligible content within the clinical findings and situations with explicit context hierarchies for which such modelling changes would apply and could be appropriately implemented. Given that this content is still subject to the outcomes of other larger content projects and additional future modelling changes, creating and assessing large interim projects would be of uncertain value.
Therefore, while awaiting the outcomes of these larger content projects, it is suggested that an interim solution be implemented with the goal of harmonizing existing content to the extent possible. At a high level, the recommendations are as follows:

• Because all relevant content currently resides within the clinical finding hierarchy, an exception could be made to the working modelling approach to allow this content to remain in the clinical findings hierarchy.
• A set of naming conventions and modelling guidelines could be applied to 1) organize this content within one hierarchical location within SNOMED CT; 2) continue the addition of new requests in a consistent manner; and 3) ensure harmonization of new content with existing content.

Naming conventions
Concepts in the Device in situ (finding) hierarchy have inconsistent naming conventions for their FSNs and descriptions. While the majority of concept FSNs have the naming pattern, "<Device> in situ," there are also concept FSNs with the pattern "<Device> present." Concepts in this hierarchy also have inconsistent description naming patterns. Examples are shown below:

It is suggested that a consistent naming pattern be applied to new requests, and for existing concepts, appropriate descriptions be added, where feasible, if they do not exist. Based on the majority of content currently in the Device in situ (hierarchy), the following naming conventions are recommended:

Modelling recommendations

1. Ensure all relevant concepts are in the Device in situ (finding) hierarchy

As previously stated, most of the existing relevant concepts are subtypes of the 397578001 | Device in situ (finding) hierarchy (please see Appendix B for a complete list of existing concepts as of the July 2015 International Release). There may also be additional concepts that should be in this hierarchy but are not; examples are listed below. This content should be considered for addition to the Device in situ (hierarchy) and modelled consistently with new and existing content.

1. Where feasible, these concepts could be modelled with the ASSOCIATED WITH attribute along with the appropriate <device> (physical object) value

While this recommendation is not as important as the first, nor would it necessarily alter the hierarchical arrangement or ancestor inheritance of these concepts, it may provide a benefit for querying SNOMED CT.
Example: A lexical search for all clinical finding concepts referencing "cardiac pacemaker" yielded 22 concepts. Of these concepts, all but 5 were found to be modelled with an ASSOCIATED WITH attribute (or one other attribute) with a value of 14106009 | Cardiac pacemaker, device (physical object). All five of these unmodelled concepts are in the Device in situ (finding) hierarchy (highlighted below in grey), suggesting that this hierarchy is under-modelled.

Presence of surgically created anatomical structure content

Similar to "Presence of <device>" content, based upon the working modelling approach, a concept following the pattern "Presence of <surgically created anatomical structure>" would also expect to be found in the situation with explicit context hierarchy. However, currently, this content is found within the clinical finding hierarchy, primarily in the Stoma finding (finding) sub-hierarchy. This is likely due to existing editorial policy prohibiting the use of a <body structure> or <morphologic abnormality> concept as the value for the ASSOCIATED FINDING attribute.
The options for modelling this content are similar to those detailed for "Presence of <device>" content. It is possible to consider expanding the allowable values for the ASSOCIATED FINDING attribute to include <body structure> concepts or to create an additional attribute in the situation with explicit context hierarchy to represent an "Associated <body structure>." However, as noted previously, each of these options would require a separate content project to fully evaluate all eligible content for which such a modelling change would apply and could be implemented. Because of the dependencies this content already has on previously noted large content projects and the high likelihood that this content is going to be re-modelled in the future, these options may cause a significant number of changes over a short period of time. Therefore, similar to "Presence of <device>" content, it is suggested that until the outcomes of the larger projects are determined, an interim solution could be implemented with the goal of harmonizing new and existing content to the extent possible. The high-level recommendations previously outlined for "Presence of <device>" content also apply to "Presence of <surgically created anatomical structure>" and detailed suggestions are provided below.
Naming conventions
FSNs of existing concepts consistently follow the pattern "<Surgically created anatomical structure> present" and, therefore, this pattern should be continued (to the degree feasible) when adding new content requests. However, since most of the new SIRS requests have been submitted with the pattern "Presence of <surgically created anatomical structure>," this pattern should be added as a description.

Modelling recommendations

1. Ensure all relevant concepts are in the Stoma finding (finding) hierarchy (as feasible)

A considerable review of SNOMED CT content was undertaken to find all concepts that could qualify for this set of concepts. This included a query for all <clinical finding> concepts with a description containing "presence" or "present" and modelled with a FINDING SITE or an ASSOCIATED MORPHOLOGY value of any subtype of either 245849007 | Post-surgical anatomy (morphologic abnormality) or 43526002 | Operative site (morphologic abnormality). As shown below, the list of concepts comprising the set of "Presence of <surgically created anatomical structure>" content is limited and most existing concepts are subtypes of the 225577002 | Stoma finding (finding) hierarchy. One concept, 302108003 | Tracheostomy present (finding) (highlighted below), is a not a subtype and should be reviewed for inclusion in this hierarchy. There are additional new content requests in SIRS and, if added, they should be added to this hierarchy as feasible (please see Appendix A for new SIRS requests).

1. Where feasible, these concepts could be modelled with the FINDING SITE attribute along with the appropriate <morphologic abnormality> value

As previously stated, this recommendation is not as important as the first, nor would it necessarily alter the hierarchical arrangement or ancestor inheritance of these concepts; however, it may provide a benefit for querying SNOMED CT. All of the above concepts above, except 302108003 | Tracheostomy present (finding), are modelled with a FINDING SITE value from the 415588005 | Stoma AND/OR site of stoma (morphologic abnormality) hierarchy and it might be beneficial to continue this modelling pattern for new SIRS requests.

Anticipated future modelling: Observable Entity Concept Model

While the above solutions provide immediately implementable modelling solutions, ultimately, this content will be dependent on the outcomes of other content projects, most notably artf231800 : Refining meaning in clinical findings, including situation, disorder, observation result and artf6283 : Observables and investigation procedures redesign
artf231800: As noted in Section 3.4.3, artf231800 aims to distinguish between multiple types of clinical content (as shown in the table below). Future changes to the clinical findings, events, situation with explicit context, and observable entity hierarchies will likely impact the modelling of "Presence of X" content.

artf6283: An important related artefact to artf231800, is the artf6283 : Observables and investigation procedures redesign project. This project defines the meanings and provides a draft concept model for observation procedures, observable entities and observation results and the relationships between them. In this draft model, observable entities represent a property or quality which is observed by an observation procedure. An observation result is the outcome of the observation procedure. Within the Observable Entity Concept Model documentation, a new attribute has been proposed to assert the context that an observation result is present or absent: the HAS VALUE attribute. The proposed HAS VALUE attribute would allow "presence" and "absence" as values to model these context assertions.
The diagram below demonstrates a specific example of how an existing concept might be remodelled in the future. (This diagram was obtained from a slide set entitled "Concept Models for observables, investigations, and observation results." This slide deck is available as an associated document for artf6283.) It is anticipated that future "Presence of X" content will be modelled in this manner. In addition, a diagram of the proposed representation of observation results for presence/absence content obtained from the Observables Redesign project can be found in Appendix D. Please see the following documents for further details regarding the Observable Entity Concept Model and modelling "presence/absence observables":

• artf6283 Observables and investigation procedures redesign inception-elaboration document
• artf6283 Presence-absence observables inception phase document

Significant design or implementation decisions / compromises

The following implementation decisions / compromises were made:

• Because "Presence of X" content is comprised of content from multiple areas (e.g., laboratory, on examination, etc.), each of which is being addressed through other content projects, it was decided (through group consensus) that the scope would be limited to "Presence of <device>" and "Presence of <surgically created anatomical structure>." In addition:
  • These two content areas were specifically noted in the CollabNet artefact description
  • These two types of content encompass the majority of the new requests in SIRS
  • These two areas allow for interim solutions which could be implemented immediately
• It was accepted that while the two content areas that were addressed ("Presence of <device>" and "Presence of <surgically created anatomical structure>") belong in the situation with explicit context hierarchy, the current editorial policy does not support this, and a compromise was made to suggest maintaining this content in the clinical finding hierarchy for the time being. The alternative – to create additional content projects to evaluate all new and existing content for which a change in editorial policy could be applied for the addition of this content in the situation with explicit hierarchy – did not seem reasonable given that this content is already subject to the outcome of other larger content projects.
• Because "Presence of X" content is significantly dependent on the outcomes of other content projects, a pragmatic decision was made to provide a short-term set of solutions which could be implemented immediately. These solutions – specific naming convention and modelling guidelines – aim to ensure consistent modelling of new and existing content.

Evaluation of Design

Exceptions and Problems

Because this content is subject to other content projects (in particular artf231800 : Refining meaning in clinical findings, including situation, disorder, observation result), it is possible that this content will be require remodelling at a future date – potentially as described in Section 6.1.1.3. Nevertheless, by maintaining a consistent modelling approach in the interim, this content will be easier to locate and re-address in the future.

Design Strengths

• The suggested modelling guidelines are consistent with URU (Understandable, Reproducible, and Useful) criteria and attempt to provide guidelines which terminology authors can reference and implement consistently when addressing this content. Furthermore, these guidelines can be implemented essentially immediately.
• The two content areas for which recommendations were provided – "Presence of <device>" and "Presence of <surgically created anatomical structure>" – comprise the majority of new "Presence of X" related content requests currently within SIRS; therefore, the proposed solutions are relevant to both new and existing content.
• The solutions address and provide solutions for modelling inconsistencies in existing content, such that when they are implemented, existing content should aggregate in the appropriate hierarchical location (where feasible). In addition, the application of consistent naming conventions should assist with user search results.

Design Weakness

This content may need to be remodelled at a future date when the outcomes of the larger content projects are implemented.

Design Risks

Recommendation

Detailed design final specification

The approach outlined in Section 6 was reviewed with IHTSDO terminology authors as well as the 2015 IHTSDO CTP leader and 2015 CTP cohort. Though this was not at the level of detail presented here it was determined that the general approach described in Section 6 was appropriate and sufficient and therefore will remain the final design specification at this time.
In summary, the recommendations aim to harmonize content and apply to both existing concepts as well as new SIRS requests to be added:

1. Until further recommendations are provided by the previously noted larger SNOMED CT content projects, an exception can be made to the existing working approach to allow "Presence of <device>" and "Presence of <surgically created anatomical structure>" content to continue to remain in the clinical findings hierarchy.

1. For "Presence of <device> content:
   1. Utilize consistent naming conventions:

1. 1. Utilize a consistent modelling approach:
      1. Ensure all relevant concepts are in the Device in situ (finding) hierarchy (see Section 6.1.1.1 for a list of existing concepts that could potentially be added to this sub-hierarchy)
      2. Where appropriate, model concepts with the ASSOCIATED WITH attribute along with the appropriate <device> (physical object) value

1. For "Presence of <surgically created anatomical structure> content"
   1. Utilize consistent naming conventions:

1. 1. Utilize a consistent modelling approach:
      1. Ensure all relevant concepts are in the Stoma finding (finding) hierarchy or other appropriate hierarchy as feasible
      2. Where appropriate, model these concepts with the FINDING SITE attribute along with the appropriate <morphologic abnormality> value

Quality program criteria

Quality metrics

Quality metric 1

Quality metric 2

Quality metric 3

Quality metric 4

Project Resource Estimates

The scope of implementation of the suggested guidelines is relatively small and, for the most part, could be implemented in one release period (depending on the number of new SIRS requests received). The following estimated number of concepts is based on existing content within the July 2015 International Release and SIRS requests at the time of this writing (September 2015):

There are currently approximately 130-160 concepts to consider. Some concepts will involve more modelling than others, depending on whether they are new or existing. If existing, concepts will also require review for missing modelling components such as descriptions or relationships. Overall, the number of existing concepts and new requests is relatively small, and therefore the impact to users is expected to be relatively low as well.
To model 2-4 concepts per hour, for 8 hours per work day, implementing the suggested guidelines would take between 4-10 days. However, please note that new requests continue to be received and that future scope is difficult to estimate. Furthermore, the recommendations are highly subject to change due to the dependencies on other content projects.
If the recommendation is accepted this would require an evaluation to take place based on the quality criteria presented above. It is suggested that this is undertaken by an IHTSDO author following editing and as part of the quality assurance of this content prior to release. Additional QA could extend the period for implementation of the recommendations.
The risks and benefits of addressing this content have been outlined in Section 4. The value in implementing the suggested guidelines is to improve consistency of modelling and harmonization of content, which should in turn result in easier, more accurate, and more consistent concept search and selection by users for recording patient data.

Projection of remaining overall project resource requirements

Expected project resource requirement category

The size of the project is relatively small and does not require project management, though there should likely be a primary terminology author and a secondary terminologist review to ensure consistently.

Expected project impact and benefit

The expected impact is not likely to be significant (i.e., small) since no major hierarchical or concept model changes are recommended. The benefit is harmonizing existing content to ensure that concepts have consistent naming conventions and are modelled in a manner that will allow them to aggregate in defined sub-hierarchies.

Appendices

Appendix A – IHTSDO SIRS Requests as of September 2015

The table below reflects all content requests associated with artf222786 in SIRS.

Requests for new concepts not specifically associated with artf222786 in SIRS, but may be related:

*Note that there are four sets of requests for new concepts that have different statuses in SIRS. These requests are listed in the table below; the status of these requests should likely be made consistent within SIRS.

Appendix B – Presence of <device> Concepts

The table below reflects the existing SNOMED CT content in the 397578001 | Device in situ (finding) sub-hierarchy. The pattern "Presence of <device>" applies to these concepts.

The table below reflects additional content for which the pattern "Presence of <device>" applies, but which is currently not in the Device in situ (finding) sub-hierarchy.

Appendix C – Presence of <surgically created anatomical structure> Concepts

The table below reflects the existing SNOMED CT content in the 225577002 | Stoma finding (finding) sub-hierarchy. The pattern "Presence of <surgically created anatomical structure>" applies to these concepts. One concept, 302108003 | Tracheostomy present (finding) (highlighted below in grey), is not a subtype and should be reviewed for inclusion in this hierarchy.

Appendix D – Proposed Observable Entity Concept Model for Observation Results

The diagram below outlines the proposed concept model for representing the presence or absence of observation results – as outlined in the slide set entitled "Concept Models for observables, investigations, and observation results" (December 26, 2014). This slide deck is available as an associated document for the content project Observable and Investigation Model Project.
https://csfe.aceworkspace.net/sf/go/artf6283?returnUrlKey=1442173204384&nav=1&selectedTab=associations

Appendix E – References

This Appendix lists titles and links to additional documentation referenced in this document:

1. artf231800: Refining Meaning in Clinical Findings, including Situation, Disorder, and Observation Result: Combined Inception and Elaboration Phases document

https://csfe.aceworkspace.net/sf/go/doc11649?returnUrlKey=1442177198771

1. artf6167 : Situation hierarchy refinement: Inception Phase document

https://csfe.aceworkspace.net/sf/go/artf6167?returnUrlKey=1442179114795&selectedTab=associations

1. artf6283 : Observables and investigation procedures redesign: Combined Inception and Elaboration Phases document

https://csfe.aceworkspace.net/sf/go/doc11647?returnUrlKey=1442173217651

1. Observable and Investigation Model Project: Presence-absence observables: Inception Phase document

https://csfe.aceworkspace.net/sf/docman/do/listDocuments/projects.observable_and_investigation_mod/docman.root.projects.presence_is_about

1. Observable and Investigation Model Project (slide set): Concept Models for observables, investigations, and observation results

https://csfe.aceworkspace.net/sf/go/artf6283?returnUrlKey=1442173204384&nav=1&selectedTab=associations

1. IHTSDO Strategic Directions to 2015

http://www.ihtsdo.org/about-ihtsdo/objectives-and-results/strategic-directions

1. IHTSDO Product/Content Development Plan (2010)

1. The IHTSDO SNOMED CT Editorial Guide (January and July 2015)

http://ihtsdo.org/fileadmin/user_upload/doc/