LINKS:

https://projects.jira.snomed.org/browse/IHTSDO-41

Document review: JIRA IHTSDO-41(artf222643) Modelling of X in remission Documentation Review (Please note this review page is not public)

Amendment History

Review Timetable

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Glossary

Domain Terms

Introduction

Purpose

The purpose of this project is to propose a Concept Model for "<disease> in remission" in SNOMED CT.

Audience and stakeholder domain

The audience for this document includes standards terminology leaders, implementers and users but is especially targeted at those stakeholders involved in the practice of oncology and mental health which are predominant domains for "<disease> in remission" content as well as authors of precoordinated SNOMED CT content and postcoordinated expressions following the recommended specification.

Input from stakeholders

As of the July 2015 International Release, there are 217 requests in SIRS related to disease in remission of which 162 were initiated since January 2013 and 79 remain active. Additionally, section 3.5 of this document on Subsidiary and Interrelated Problems addresses a number of related projects which indicate a user need to describe disease behaviors over time.

Degree of consensus on the statement of problem

There appears to be consensus on the need for a Concept Model to represent "<disease> in remission".
Areas where consensus is yet to be achieved include:

1. Whether "<disease> in remission" should be a subtype of |Disease (disorder)| or a subtype of 413350009 |Finding with explicit context (situation)|

2. The extent to which "<disease> in remission" content should be precoordinated in SNOMED CT.

Statement of the problem or need

Summary of problem or need, as reported

Description of the problem as per the Content Tracker artf222643 Modeling of "X in remission":

• Should "remissions" be modeled as "situations" instead of "disorders"

• If modeled as "situations" identify a template to be used for concept definitions

Summary of requested solution

A solution was not proposed with the initial request. However, in August 2011, the IHTSDO Chief Terminologist offered the following insight:
"A disease X in remission is not a separate kind of disease X, it is a status of the disease course.
In prior terminologies (SNOMED RT, CTV3) there was no situation hierarchy, so remission concepts were put in as subtype in the Is-a hierarchy of disease.
I would model disease in remission as a situation. Instead of modeling the fact that some disease manifestation is absent (exactly what must be absent, in order to achieve remission, varies from disease to disease), it seems it would be wise to assert a positive about disease phase. One modeling possibility is perhaps to activate the attribute "disease phase" as an attribute that can be used in the situation hierarchy, and model "disease phase" = "remission phase".
In other words, we would say that "schizophrenia in remission" is a situation, with associated-finding = schizophrenia, finding-context = known present, and disease-phase = remission phase."

Statement of problem as understood

A Concept Model is needed to represent "<disease> in remission".
Challenges include:

• Determining the context in which "In remission" has a meaning that can be consistently represented by the Concept Model and, in particular, whether the following two specific categories of remission can be modeled with one model.

  • Remission in response to treatment

  • Spontaneous remission as a natural disease process

• Developing the Concept Model for representing "<disease> in remission" including:

  • Determining whether "<disease> in remission" should be represented in the |Disease (disorder)| or |Finding with explicit context (situation)| hierarchy

  • Determining whether there is a reproducible boundary between disease stages, phases and courses and into which of those "In remission" falls.

  • Integrating the approach to modeling "<disease> in remission" with the approach for other similar disease characteristics (e.g., status, course, phase etc.)

• Determining the appropriate level of granularity (e.g., early remission, partial remission, complete remission) for precoordination of "<disease> in remission" content in SNOMED CT

Detailed analysis of reported problem, including background

Determining the context in which "In remission" has a reproducible meaning

A key issue in considering a model for "<disease> in remission" is whether there is a disease context in which "In remission" has a reproducible meaning that can be consistently represented with one Concept Model.
Examples of the varied clinical contexts in which remission is used include:

1. Remission as part of the natural history of a disease (e.g., spontaneous remission)

2. Remission as a response to treatment of a disease

3. Remission in disorders with very objective measures of disease (e.g., signs observed on examination or by testing)

4. Remission in disorders with more subjective measures of disease (e.g., some behaviors and mental health disorders/findings)

The SNOMED CT concepts qualified with "in remission" and the related requests in SIRS are varied. However, two common categories of content qualified with "in remission" include:

• Chronic, generally progressive diseases which may or may not be curable (e.g., malignancies)

• Behavior and mental health disorders which may or may not be progressive

Examples of "in remission" as a modifier for findings/disorders
Concepts in bold are already in SNOMED CT. Concepts in italics represent SIRS requests not yet added as of the July 2015 release (which generally have their origins in ICD codes):

•  

  • Ulcerative colitis in remission (disorder)

  • Leukemia in remission (disorder)

  • Eating disorder in remission (disorder)

  • Schizophrenia in remission (disorder)

  • Cocaine dependence in remission (disorder)

  • Postpartum major depression in remission (disorder)

  • Peer problems in remission (finding)

  • Relationship problems in remission (finding)

  • Codependency in remission (finding)

  • Bereavement in remission (finding)

  • Alcohol dependence in early full remission (disorder)

  • Compulsive gambling in remission (disorder)

  • Age related cognitive decline in remission (disorder)

Definition of Remission

Specific criteria and definitions for remission may vary by disease or specialty. Most definitions include some variation of Dorland's general definition

:

1. Diminution or abatement of symptoms of a disease

2. The period during which such diminution occurs

The first definition above describes the disease state, whereas the second describes the period of time during which the state occurs.
Other definitions for remission are increasingly granular. For example:

• Diminution or abatement of signs and symptoms of a disease

• Diminution or abatement of sign and symptoms of chronic or malignant diseases

• Diminution or abatement of sign and symptoms of chronic or malignant diseases in response to treatment

• Diminution or abatement of sign and symptoms of incurable, chronic or malignant diseases in response to treatment

Essentially all definitions for remission include some type of lessening of symptoms. While terms like "diminution", and "abatement" generally imply a change in the nature of the disease, they also insinuate that the disease is ongoing. Remission is not a cure, it is temporary. It can be partial or complete and can occur spontaneously or as a response to treatment.
For the purpose of trying to move forward with this model, it is it is suggested that SNOMED CT use the following definitions:
In remission: the period in the course of a disease/condition during which there is temporary lessening or abatement of signs and/or symptoms of the disease
This definition does not constrain the meaning of remission with respect to how the remission was achieved (spontaneous or in response to treatment).
In partial remission the period in the course of a disease/condition during which the signs and/or symptoms of the disease have temporarily lessened but remain present/detectable to some degree
In complete remission the period in the course of a disease/condition during which the signs and/or symptoms of the disease are temporarily no longer present/detectable. Complete remission is not a cure.
In spontaneous remission the period in the course of a disease/condition during which there is unexpected (in the absence of treatment) lessening or abatement of the signs and/or symptoms of the disease. In some disease contexts, this is also called spontaneous regression.
Remission is followed by disease relapse or recurrence which are also terms that may have different meanings in different contexts. Defining the meaning of relapse and recurrence is not part of this project. However, they are considered here because the model for "<disease> in remission" should logically extend to other phases which are also part of the natural course of a disease. Although some of the other disease phases (e.g., prodrome, convalescence, incubation etc.) are minimally used as disease descriptors in SNOMED CT, recurrence and relapse are used for several hundred concepts. For this reason, the definitions for relapse and recurrence, although not being suggested as part of this project, are presented here. In particular, this creates a significant dependency on the outcome of the project related to artf6221: Recurrent malignant neoplasm.
Relapse (as a phase) the period in the course of a disease/condition that follows remission (or an interval of improvement) during which there is a reappearance of the signs and/or symptoms of the disease
Recurrence of disease and recurrent disease are terms with significant ambiguity in clinical use. Two possible uses are provided.
Recurrence of disease the return of signs and/or symptoms of a disease/condition after remission

.
Recurrent disease is often used to refer to an entirely new episode (e.g., a separate disease) of a disease/condition which the patient has previously experienced (e.g., |Recurrent miscarriage (disorder)|, |Recurrent bacterial cystitis (disorder)|, |Recurrent pneumonia (disorder)|).
However, for malignancies, the return of the original disease can be called a recurrence (e.g., |Local recurrence of malignant tumor of colon (disorder)|). In some contexts, this may also be called recurrent malignant disease (e.g., recurrent multiple myeloma).
Determining when "recurrence of <disease>" and "recurrent <disease>" represent a disease phase that follows remission in the course of a single disease as opposed to a disease that represents an entirely new episode of a previously experienced disease can be challenging (see artf6221: Recurrent malignant neoplasm).
This project has a general dependency on many of the projects listed in Section 3.5 which address modeling of disease courses and phases. For example, the model for |Chronic disease (disorder)| in SNOMED CT is also quite relevant because, often, remission is a phase in a chronic disease. Therefore, consideration should also be given to how the model for remission will be integrated with the model for chronic disease. (See project related to artf222304 & artf222305 Review "Chronic respiratory disease in perinatal period" as a chronic condition & Review "Lichen simplex chronicus" as a chronic condition). The dependencies on other projects will be further addressed in Section 3.4.2 on the Concept Model for representing "<disease> in remission".

The Concept Model for representing "<disease> in remission"

The concept model for "<disease> in remission" requires:

• Determining whether "<disease> in remission" should be represented in the |Disease (disorder)| or |Finding with explicit context (situation)| hierarchy

• Determining whether there is a reproducible boundary between disease courses, phases and stages and into which of those "remission" falls

• Integrating the model for "<disease> in remission" with the approach for modeling other similar qualifiers that describe disease status/behavior over time (e.g., recurrence of disease)

Representation of "<disease> in remission" as a |Disease (disorder)| or a |Finding with explicit context (situation)|

The issue of whether "<disease> in remission" should be represented in the |Disease (disorder)| hierarchy or the |Finding with explicit context (situation)| hierarchy requires consideration of how "<disease> in remission" has been modeled in SNOMED historically as well as how similar content is being modeled or will be modeled going forward.
Since 2004, SNOMED CT editorial policy guidance on the |Disease (disorder)| hierarchy has provided the following three criteria related to disorders (from the July 2015 SNOMED CT Editorial Guide Section 6.1.1.1 Disorders):

1. Disorders necessarily are abnormal.

2. They have temporal persistence, with the (at least theoretical) possibility of their manifestations being treated, in remission, or quiescent even though the disorder itself still present.

3. They necessarily have an underlying pathological process

Criteria #2 aligns with the proposed definition of "In remission" in that it specifically addresses the idea that a disorder is still considered to be present even when it is in remission. It also establishes that that the existing approach has been to represent "<disease> in remission" in the |Disease (disorder)| hierarchy.

Representation of "<disease> in remission" as a |Finding with explicit context (situation)|

One suggestion on the Content Tracker proposes modeling "<disease> in remission" as a situation (in the |Finding with explicit context (situation)| hierarchy). From the Content Tracker on 10/18/2011:
Instead of modeling the fact that some disease manifestation is absent (exactly what must be absent, in order to achieve remission, varies from disease to disease), it seems it would be wise to assert a positive about disease phase. One modeling possibility is perhaps to activate the attribute "disease phase" as an attribute that can be used in the situation hierarchy, and model "disease phase" = "remission phase".
The above approach for representing "<disease> in remission" as a situation proposes making 278174000 |Disease phase (attribute)| an approved attribute with a range of 303105007 |Disease phases (qualifier value)|.
Following the above proposal, "<Disease X> in remission" might be modeled:

=== |Clinical finding present (situation)| :

            { |Associated finding (attribute)| =  |Disease X (disorder)|,

               |Temporal context (attribute)| = |Current or specified time (qualifier value)|,

               |Finding context (attribute)| = |Known present (qualifier value)|,

               |Subject relationship context (attribute)| = |Subject of record (person)|

 |Disease phase (attribute)| = Remission phase (qualifier value) }

The July 2015 value set for |Disease phases (qualifier value)| includes:

• Accelerated phase (qualifier value)

• Acute phase (qualifier value)

• Chronic phase (qualifier value)

•  Convalescent phase (qualifier value) 

• Prodromal phase (qualifier value) 

• Relapse phase (qualifier value) 

• Remission phase (qualifier value) 

  • In complete remission (qualifier value) 

  • In partial remission (qualifier value) 

• Transformed phase (qualifier value)

Potential issues related to |Disease phases (qualifier value)| and the proposal to make |Disease phase (attribute)| an approved attribute include:

1. The set of values for | Disease phases (qualifier value) | may be relative to the diseases that they qualify. For example, the phases for infectious diseases are different than the phases for malignant diseases. Therefore, determining the value set and the hierarchical ranking of the values may be challenging. 

2. While spontaneous remission is a naturally occurring disease phase, remission in response to treatment (the more likely meaning when applied to malignant diseases) is actually a treatment response rather than a naturally occurring disease phase. (The same may be true for |Convalescent phase| in some cases.)

3.  If | Disease phase (attribute) | is made an approved attribute, a review of existing SNOMED CT content indicates that several of the values in the | Disease phases (qualifier value) | value set would only apply to few (if any) existing disease concepts. For example, as of the July 2015 Release, there are only 2 disorders in SNOMED CT concept with "prodromal" in their FSNs.

4. The values in the set which might have a broader use include:

These values overlap to some degree with values in the |Courses (qualifier value)| hierarchy and this overlap may lead to further inconsistency in concept definitions.

Examples:

• |Acute phase (qualifier value)| versus |Sudden onset AND short duration (qualifier value)| This might contribute to the existing ambiguity as to the meaning and model of Acute <disease> (as described in section 3.4.3.1) 

• |Relapse phase (qualifier value)| versus |Relapsing course (qualifier value)| |Relapse phase (qualifier value)| and |Relapsing course (qualifier value)| have dependencies on the model being developed for “recurrence of <disease>”.

5. Modeling of similar “disease status” content

Earlier proposals that suggested representing "<disease> in remission" as a situation modeled with |Disease phase (attribute)| suggested that other disease status concepts should also be situations. This would increase the scope of the task significantly. Recommended content to be moved to situations in a document titled "Event-condition-episode_notes-ks.doc" (see Appendix D - <disease> status notes) included:

• In remission, in relapse, in partial/complete remission -> disease phase (attribute)

• In control, not in control, in poor control, in good control -> NEW attribute needed.

• Disease phase (acute phase, convalescent phase, etc.) -> disease phase (attribute)

• Severity (mild, moderate, severe) -> severity (attribute)

• Stage -> staging of disease (attribute)

• Episodicity -> episodicity (attribute)

Many of the issues related to |Disease phases (qualifier value)| are similar to issues that impact the URU of |Clinical course (attribute)| and its value set |Courses (qualifier value)| which will be discussed in more detail in subsequent sections.

Representation of "<disease> in remission" as a |Disease (disorder)|

Representing "<disease> in remission" in the |Disease (disorder)| hierarchy might be an alternative solution to representing "<disease> in remission" as a |Finding with explicit context (situation)| for the following reasons:

1. In the |Disease (disorder)| hierarchy, "<disease > in remission" could also be modeled using either |Disease phase (attribute)| or |Clinical course (attribute)| with the value "In remission". Other options might include assigning stated high-level "Disease in remission" grouper concepts.

2.  Several hundred "<disease> in remission" concepts are already in the |Disease (disorder)| hierarchy where "<Disease X> in remission" is generally a subtype of "Disease X". 

3. Concepts representing disease characteristics similar to "In remission" are already largely represented in the |Disease| hierarchy.

   1. These include; disease course (e.g., chronic, relapsing), disease control status (e.g., poor, progressive, refractory, intractable, active), and disease severity and episodicity

   2. Similar content continues to be added to the |Disease| hierarchy (e.g., |Severe persistent asthma controlled co-occurrent with allergic rhinitis (disorder)|) 

4. If "<disease> in remission" is represented in the |Finding with explicit context (situation)| hierarchy, determining which of the similar, existing disease course/process/status/phase concepts should also be moved to the |Finding with explicit context (situation)| hierarchy would be an arduous (if not nearly impossible) task that is unlikely to be completed in the near future. In the interim, a lack of consistency in the modeling of similar content could present a barrier to implementation.

For example, changing |Single manic episode in full remission (disorder)| to a |Situation with explicit context| while leaving its similar siblings as subtypes of |Manic disorder, single episode (disorder)| will not facilitate implementation.

5. "<disease> in remission" content is somewhat similar to content in the |Evaluation finding (finding)| hierarchy which represents evaluation results.

Determining whether there is a reproducible boundary between disease courses, phases and stages and into which of those "<disease> in remission" falls

An additional consideration in the model for "<disease> in remission" is whether to represent remission as part of the disease course, as a disease phase or as a disease stage.
Some historical indicators of previous difficulties in determining the appropriate attribute and hierarchy for the concept model for "<disease> in remission" include:

1. 70919002 |In remission (qualifier value)| was once an allowed value for |Severity (attribute)| but it was later retired as |Ambiguous concept| with |MAY BE A| relationships to |Remission phase (qualifier value)| and |Patient in remission (qualifier value)|).

2. 110279003 |Inactive disease following therapy (finding)| is a concept in SNOMED CT.

   1. This is a similar concept to "<disease> in remission in response to treatment"

   2. |Inactive disease following therapy (finding)| previously had a description “Disease in remission” which was retired (possibly because not all remissions follow therapy).

   3. |Inactive disease following therapy (finding)| is currently a subtype of |General finding of observation of patient (finding)| but it was formerly a |Context-dependent finding (finding)| which is now retired and a synonym for |Finding with explicit context (situation)|. Thus, the debate as to whether this type of concept should be a finding or a situation is not new.

An initial reasonable approach might be to continue to model "<disease> in remission" concepts in the |Disease| hierarchy using |Disease phase (attribute)| to model "In remission" as a phase in the course of a disease. However, because definitions for disease phases/stages may be relative to the disease they qualify, it may be difficult to determine the value set for |Disease phase| and a hierarchical order for the values that is consistent for all diseases. Examples: