Many disorders can occur in combination within the same patient. Guidance on the modeling and terming of FSNs for disorder combinations aims to achieve consistency. Clinically significant disorder combinations are represented in SNOMED CT by a single concept so that users can document temporal (timing) and causal (cause/effect) relationships between the conditions.
To express an association between conditions, one of the following associations is used:
Simple co-occurrence: two or more conditions have no direct causal or temporal relationship but are found together more often than by random chance
Causation 1: the cause is another finding or disorder, an event, or procedure
Causation 2: the cause is a physical force, physical object, organism, or substance
When considering disorder combinations two questions can be asked:
The following table provides the possible combinations of answers. It allows authors to assign combination disorders to a corresponding category below, to which the appropriate modeling and FSN construction is applied.
Is there a stated causal relationship?
Yes, the cause is another finding or disorder, an event, or procedure.
This is causation 1.
Yes, the cause is a physical object or force, organism, or substance.
This is causation 2.
What is the temporal relationship?
X due to Y
X caused by Y
X and Y should be documented separately
X follows Y
X due to and following Y
X after Y
X precedes Y
X before Y
X before Y
X occurs during Y
X due to and during Y
X during Y
X occurs before, during, and/or after Y
X due to and temporally related to Y
X temporally related to Y*
*Note: Temporally related to (attribute) and its subtypes Before and During are only approved to model perioperative complications and a limited number of other clinical findings.
Assign each condition as a supertype (or ensure that each participating disorder is present in the ancestor tree following classification)
Use simple co-occurrence for two or more conditions that are strongly associated by means other than causality or a temporal relationship (e.g. a common predisposition) where representing such conditions as separate statements would result in a loss of the associated between the conditions
Do not use simple co-occurrence for those disorders with more than one anatomical site or more than one associated morphology. Those disorders should rather be represented as individual concepts in a medical record.
FSN: X with Y
Sinusitis with nasal polyps (disorder)
Acute bronchitis with bronchiectasis (disorder)
|Incorrectly named legacy examples (not to be repeated):|
Psoriasis-eczema overlap condition (disorder)
Hay fever with asthma (disorder)
Be aware of conditions which likely exist prior to a disorder or procedure.
For example, legacy term 609454008 | Induced termination of pregnancy complicated by acute necrosis of liver (disorder)|
|Cause is another finding, disorder, event, or procedure|
For a condition caused by a clinical finding/disorder
For a condition caused by a procedure
For a condition caused by an event
For conditions that are causal, or causal and co-occurring, construct the FSN with due to
For conditions specified as causal and temporal, construct the FSN with due to and the temporal relationship
735173007 | Shock due to anaphylaxis (disorder)| is an example of a condition caused by a clinical finding/disorder. Because the shock and the anaphylaxis are co-occurring, both conditions are represented in the supertypes and axioms, in addition to the Due to relationship.
413532003 | Anemia due to blood loss (disorder)| is an example of a condition caused by a clinical finding/disorder. Because the bleeding could have been controlled and thus not necessarily present, only causation is modeled in this concept. The blood loss/bleeding is not represented as a supertype.
Incorrectly named legacy examples (not to be repeated):
Neutropenia associated with acquired immunodeficiency syndrome (disorder)
Dilated cardiomyopathy secondary to granuloma (disorder)
Determining causation only versus causation and co-occurrence
There are no heuristics to standardize the determination of a precoordinated combination modeled using only the Due to relationship versus modeling the Due to relationship in addition to representing the causative condition in the supertypes. If both conditions must be present for the other to occur, both should be represented in the supertypes. Whether both conditions must be present concurrently is determined by an understanding of the disease process. Considerations include whether the conditions are chronic diseases, as these types of conditions will be ever present and thus require representation in the supertypes. If the causing condition resolves but the resultant condition can remain, then representation of both conditions in the supertypes is unwarranted.
There are approximately 425 legacy concepts with 'co-occurrent and due to' in the description. Do not add new concepts with the terming 'co-occurrent and due to', instead use co-occurrence modeling (both conditions are represented in a supertype) in addition to the Due to (attribute) if warranted by the clinical condition.
Umbilical cord complication
Causation 2 is when 1the cause is a material entity, and 2the means of exposure/introduction are not significant.
Assign the caused disorder (X) as a supertype, or ensure that the caused disorder is a supertype following classification
Assign the causal factor (Y) as the value of a Causative agent (attribute)
X caused by Y
Incorrectly named legacy examples (not to be repeated):
Choking due to airway obstruction (finding)
Coma associated with diabetes mellitus (disorder)
Laser-induced burn (disorder)
|Temporal sequencing without causation|
Assign the condition or procedure that occurred first in the patient as the target of an After (attribute) relationship. Assign the condition that occurred second as a supertype (or ensure its presence in the ancestor tree).
402490007 |Calcinosis following localized fat necrosis (disorder)|
The fat necrosis occurred first in the patient, so this concept will have an After (attribute) with a value of Fat necrosis (disorder). The calcinosis occurred secondarily, and thus Calcinosis (disorder) is a supertype of this concept.
16055031000119100 |Astigmatism of right eye following operative procedure (disorder)|
The operative procedure occurred first in the patient, so this concept will have an After (attribute) with a value of Surgical procedure (procedure). The astigmatism occurred secondarily, so Astigmatism (disorder) is a supertype of this concept.
Where X occurs after Y:
Not all disorders occurring in combination should be precoordinated into a single concept. Multiple clinical conditions should not be precoordinated in order to facilitate convenient recording in the medical record, even if the two conditions are often reported together.
In general, 47429007 |Associated with (attribute)| should be avoided due to the ambiguity which it conveys and the difficulty in applying this role consistently. Instead, Due to is used when there is a direct causal relationship between the conditions; otherwise, the clinical conditions should be recorded as separate concepts in the medical record.
There are a couple of exceptions when the use of 47429007 |Associated with (attribute)| is appropriate:
e.g. 6211002 |Polyarthritis associated with another disorder (disorder)| subsumes two children
201972000 |Allergic arthritis of multiple sites (disorder)| modeled with 42752001 |Due to (attribute)| of 419076005 |Allergic reaction (disorder)|
422565003 |Post-infective polyarthritis (disorder)| modeled with 255234002 |After (attribute)| of 40733004 |Infectious disease (disorder)|
It must be determined if a disorder is caused either by another disorder or by a material entity. A material entity is a concept found in Substance, Physical object, Pharmaceutical/biologic product, Physical force, or Organism subhierarchies. These subhierarchies are the current range constraints for the Causative agent (attribute) in the Clinical finding domain. For combined disorders where a cause can be either a disorder (eg, alcoholism) or a material entity (eg, alcohol):
Model as due to disorder if it is the indirect cause.
Model as caused by material entity if it is the direct cause.
In modeling concepts related to infectious diseases, a number of considerations need to be taken in to account.
Firstly, when the disorder is an infectious disease itself, and the organism is specified, then the concept will be modeled with
Secondly, Disorders can be modeled with |Due to|, |After| or |Due to| and |After| relationships to infectious diseases. Note If the focus disorder is itself an infectious disorder, it will also have a |Causative agent| relationship when the organism is specified.
|Causative agent| relationship: 721742004 |Otitis media caused by Streptococcus pneumoniae (disorder)|
|Due to| relationship: 698733009 |Intestinal obstruction due to tuberculosis (disorder)|
|Due to| and |Causative agent| relationship: 866044006 |Mycosis due to human immunodeficiency virus infection (disorder)|
|After| relationship: 182961000119101 |Acute disseminated encephalomyelitis following infectious disease (disorder)|
|After| and |Causative agent| relationship: 4740000 |Herpes zoster (disorder)|
|Due to| and |After| relationship: 1148594002 |Chronic arthritis due to and following rheumatic fever (disorder)|
|Due to| and |After| and |Causative agent| relationship: 15992311000119100 |Keratitis of left eye due to herpes zoster (disorder)|
Applying the |Due to|, |After| or |Due to| and |After| relationships to a concept will not lead to it being a subtype of |Infectious disease (disorder)| unless it is itself an infectious disease.
Exceptions may exist to the above guidance which requires review on a case-by-case basis.
The FSN submitted by a requestor may be used as preferred term even if it does not comply with the above recommended pattern. However, do not use phrases such as secondary to, as a result of, etc. in lieu of due to.
Rather than the naming conventions described above, use the names that are accepted clinical parlance and that represent specific pathophysiologic entities for some combined disorders, as the preferred term.
Disorder combination modeling
(See also, Appendix, Concept Models: Disorder Combinations)