SNOMED Documentation Search


 Other Documents

Versions Compared

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

The SNOMED CT hierarchy

The SNOMED CT 

Gloss
PreSpacefalse
tsubtype hierarchy
 refers to the organization of
Gloss
PreSpacefalse
tconcepts
in
Gloss
PreSpacefalse
tSNOMED CT
from the most general concepts, at the top of the
Gloss
PreSpacefalse
thierarchy
, to the more specific concepts at the bottom. The
Gloss
PreSpacefalse
tconcepts
that make up the top level of the
Gloss
PreSpacefalse
thierarchy
are shown in 
Caption reference
CapRefIdtop-level
CapRefTypeTable
 . All other 
Gloss
tactive concepts
 are subtypes of at least one of these concepts.


Caption label
CapIdtop-level
CapTypeTable
Top Level
  • Concept
    t404684003|Clinical finding|

  • Concept
    t71388002|Procedure|

  • Concept
    t363787002|Observable entity|

  • Concept
    t123037004|Body structure|

  • Concept
    t410607006|Organism|

  • Concept
    t105590001|Substance|

  • Concept
    t373873005|Pharmaceutical / biologic product|

  • Concept
    t123038009|Specimen|

  • Concept
    t370115009|Special concept|

  • Concept
    t106237007|Linkage concept|

  • Concept
    t78621006|Physical force|

  • Concept
    t272379006|Event|

  • Concept
    t308916002|Environment or geographical location|

  • Concept
    t48176007|Social context|

  • Concept
    t243796009|Situation with explicit context|

  • Concept
    t254291000|Staging and scales|

  • Concept
    t260787004|Physical object|

  • Concept
    t362981000|Qualifier value|

  • Concept
    t419891008|Record artifact|

Several levels of increasingly fine categorization may exist between the top level of the

Gloss
PreSpacefalse
thierarchy
and
Gloss
PreSpacefalse
tconcepts
that have sufficient detail to be recorded in a patient's medical record. shows the levels of
Gloss
PreSpacefalse
thierarchy
that exist between the top-level
Gloss
PreSpacefalse
tConcept
Concept
t404684003|Clinical finding|
ShowFormatinline
and the finding "Catatonic reaction."


Caption label
CapIdhierarchy-example-catatonic-reaction
CapTypeFigure
Hierarchy example: Catatonic Reaction

Hierarchy Representation in the relationships table

The

Gloss
PreSpacefalse
tSNOMED CT Relationship
table represents
Gloss
PreSpacefalse
trelationships
between one
Gloss
PreSpacefalse
tSNOMED CT concept
and another by including a row in the table for each such
Gloss
PreSpacefalse
trelationship
. The columns
Specref
RefTypefield
tsourceId
,
Specref
RefTypefield
ttypeId
and
Specref
RefTypefield
tdestinationId
define the source of the
Gloss
PreSpacefalse
trelationship
, the kind of
Gloss
PreSpacefalse
trelationship
that exists and the target of the
Gloss
PreSpacefalse
trelationship
respectively. Each of these fields, contains a
Gloss
PreSpacefalse
tSNOMED CT Concept
Gloss
PreSpacefalse
tIdentifier
. Hierarchical
Gloss
PreSpacefalse
trelationships
are expressed by linking the source
Gloss
PreSpacefalse
tconcept
to its "parents" (i.e. the
Gloss
PreSpacefalse
tconcept
or
Gloss
PreSpacefalse
tconcepts
immediately above it in the
Gloss
PreSpacefalse
thierarchy
). The
Specref
RefTypefield
ttypeId
used to represent the
Gloss
PreSpacefalse
tsubtype hierarchy
is the
Concept
t116680003|is a|
ShowFormatinline
Gloss
PreSpacefalse
trelationship
.

For example, the fact that 

Concept
ShowPartsterm
t102909009|catatonic reaction|
ShowFormatinline
 is a subtype of 
Concept
ShowPartsterm
t116367006|psychological finding|
 is expressed in the
Gloss
PreSpacefalse
tRelationship
Table as shown in 
Caption reference
CapRefIdsubtype-relationship
CapRefTypeTable
:

Caption label
CapIdsubtype-relationship
CapTypeTable
Subtype Relationship Example

Specref
RefTypefield
tsourceId

Specref
RefTypefield
ttypeId

Specref
RefTypefield
tdestinationId

Concept
ShowPartsid
t102909009|Catatonic reaction (finding)|

Concept
ShowPartsid
t116680003|Is a (attribute)|

Concept
ShowPartsid
t116367006|Psychological finding (finding)|

Where the identifiers shown above represent the following concepts:

  •  

    Concept
    t102909009 catatonic reaction|

  •  

    Concept
    t116680003 is a
    ShowFormatinline

  •  

    Concept
    t116367006 psychological finding|
    .

Following these relationships in the opposite direction (i.e. from destinationId to sourceId) we can find all the

Gloss
PreSpacefalse
tsubtype children
of a concept.

Using "is a" Relationships to enhance search capabilities

This section is concerned with the ways in which the

Gloss
PreSpacefalse
thierarchy
can be used to help a
Gloss
PreSpacefalse
tSNOMED CT
user when they are searching or browsing the terminology.

Note: The primary use of the

Gloss
PreSpacefalse
tSNOMED CT
Gloss
PreSpacefalse
tsubtype
Gloss
PreSpacefalse
thierarchy
is to support effective retrieval and aggregation of data. This is discussed in
Gloss
PreSpacefalse
tTesting and traversing subtype relationships
.

It is possible to start at the top of

Gloss
PreSpacefalse
thierarchy
and navigate from parent to
Gloss
PreSpacefalse
tchild
in order to find a
Gloss
PreSpacefalse
tConcept
or
Specref
RefTypefield
tterm
in
Gloss
PreSpacefalse
tSNOMED CT
. A more efficient approach, however, is to use the
Gloss
PreSpacefalse
thierarchy
to supplement a
Specref
RefTypefield
tKeyword
search by enabling the user to look at related
Gloss
PreSpacefalse
tConcepts
in order to consider them as alternative matches, or to check the context of a search result. The following examples illustrate these two uses of the
Gloss
PreSpacefalse
tSNOMED CT
Gloss
PreSpacefalse
thierarchy
.

Example:

  1. Checking supertypes
    • A user wishes to find a

      Gloss
      PreSpacefalse
      tdescription
      that relates to the condition of a patient who is hypersensitive to an allergen. The user performs a search on the
      Specref
      RefTypefield
      tKeyword
      "Hypersensitivity" and finds an exact match. Before the user selects the
      Gloss
      PreSpacefalse
      tdescription
      for inclusion in the patient record, they check the
      Gloss
      PreSpacefalse
      tFully Specified Name
      , which is "Sensitivity (finding)." The user then checks the
      Gloss
      PreSpacefalse
      thierarchy
      and discovers that the selected
      Gloss
      PreSpacefalse
      tConcept
      has "Psychological finding" as an
      Gloss
      PreSpacefalse
      tancestor
      , which indicates that this is not the correct
      Gloss
      PreSpacefalse
      tdescription
      to use in this context.

  2. Checking

    Gloss
    PreSpacefalse
    tsubtypes
    :
    Anchor
    _b261a940-2e45-4362-bff4-6c837e6f1cd9__1
    _b261a940-2e45-4362-bff4-6c837e6f1cd9__1

    • A user wishes to find a

      Gloss
      PreSpacefalse
      tdescription
      that relates to the condition of a patient who is hypersensitive to an allergen. The user searches for the
      Specref
      RefTypefield
      tKeyword
      "allergy," and finds one
      Gloss
      PreSpacefalse
      tConcept
      having a
      Gloss
      PreSpacefalse
      tdescription
      that is an exact match. The user then looks at the
      Gloss
      PreSpacefalse
      tchildren
      of the
      Gloss
      PreSpacefalse
      tConcept
      (i.e. those
      Gloss
      PreSpacefalse
      tconcepts
      immediately below it in the
      Gloss
      PreSpacefalse
      thierarchy
      ). One of the
      Gloss
      PreSpacefalse
      tchildren
      has the preferred
      Gloss
      PreSpacefalse
      tdescription
      "Contact Hypersensitivity" which matches the user's intended meaning. The user selects this
      Gloss
      PreSpacefalse
      tConcept
      for inclusion in the patient record.

Using "is a" Relationships to display hierarchical information in applications

Most visual application development tools contain a

Gloss
PreSpacefalse
tcomponent
designed to display hierarchical information as a tree in which branches can be expanded or collapsed. Tree views are well-suited to displaying
Gloss
PreSpacefalse
tSNOMED CT
hierarchical
Gloss
PreSpacefalse
tRelationships
(see
Caption reference
CapRefIdhierarchy-as-tree
CapRefTypeTable
). These views are used in many different user-interfaces where information needs to be represented as a hierarchy (e.g. displaying a file-system as a hierarchy of folders or providing a collapsable outline of a document or help file). Therefore, most users will already be familiar this paradigm.

Caption label
CapIdhierarchy-as-tree
CapTypeFigure
SNOMED CT hierarchy represented in a tree view


The process of creating a tree view from the

Gloss
PreSpacefalse
tSNOMED CT Relationship
table is straightforward as long as a few simple ideas are mastered:

  • Most standard tree-views controls start from a single root and require that higher level branches must be added before sub-branches. This means that when viewing part of the

    Gloss
    PreSpacefalse
    thierarchy
    from the bottom up, the tree must be compiled in temporary form before it can be displayed.

  • Since the depth of the

    Gloss
    PreSpacefalse
    thierarchy
    is not known in any particular case, operations that iterate up or down the depth of the
    Gloss
    PreSpacefalse
    thierarchy
    must be done using a recursive algorithm. However, this recursion must usually be limited since placing the entirety of the
    Gloss
    PreSpacefalse
    tSNOMED CT
    hierarchy in a single tree control is likely to create performance issues and may exceed physical limits on the capacity of the control.

  • Standard tree view controls are not good at displaying the multiple parent nodes that occur in a

    Gloss
    PreSpacefalse
    tpolyhierarchy
    like
    Gloss
    PreSpacefalse
    tSNOMED CT
    . Therefore, some compromises need to be made to present options for navigation up the hierarchy.

  • Effective use of some tree controls requires unique keys for each node. Multiple parents and multiple roots through the hierarchy mean that the same

    Gloss
    PreSpacefalse
    tConcepts
    will appear in multiple places in the hierarchy. Therefore, the
    Gloss
    PreSpacefalse
    tconcept identifier
    cannot be used to provide a key that is globally unique within the hierarchy.