Subject Participation and Subject Relationship Context
The HL7 participation type “subject” relates a finding or procedure to a subject who may or may not be the subject of the record. This allows specific named individuals to be identified as the subject of an Act. It can also be used to associate a related person by specifying their relationship rather than by identifying them. For example [ 303071001 | person in the family ], [ 72705000 | mother], [ 70862002 | contact person], etc.
The SNOMED CT [ 408732007 | subject relationship context ] attribute provides a mechanism for indicating that the subject of a procedure or finding is a person (or other entity) related to the subject of the record. This facility is used to define some SNOMED CT concepts (e.g. "family history of asthma" has [ 408732007 | subject relationship context ] = [ 303071001 | person in the family ]). The same attribute can also be used to create post-coordinated expressions. For example, it can be used to express a family history of a disorder without requiring the a concept that expresses a family history of that particular disorder. Unlike the HL7 "subject" participation, the SNOMED CT mechanism does not directly support reference to an identified person.
The following rules are specified to encourage explicit recording of the [ 408732007 | subject relationship context ] in order to minimize risks of overlooking this aspect of the information.
- When using SNOMED CT to represent an observation or procedure that applies to a subject other than the record target, the appropriate [ 408732007 | subject relationship context ] SHOULD be specified in the SNOMED CT expression.
- For example "family history" should be represented using an expression that specifies the [ 408732007 | subject relationship context ] as [ 303071001 | person in the family ].
- The HL7 subject participation MAY also be used and SHALL be used if there is a requirement to specifically identify an individual subject.
- If the HL7 subject participation is used in addition to the SNOMED CT representation of [ 408732007 | subject relationship context ], the Role.code of the role that is the target of the subject SHOULD be represented using SNOMED CT with the value applied to the [ 408732007 | subject relationship context ] or with a subtype of that value.
These recommendations leave some situations in which either approach may be used. Therefore, to compute equivalence, a map between the values used in the code attribute of the associated subject role is required. The simplest option would be to specify that when the classCode attribute of the HL7 Role specifies "personal relationship" the code attribute should have a value from the SNOMED CT [ 408732007 | subject relationship context ] hierarchy.
Ambiguity may be introduced if the information is coded using a concept with explicit [ 408732007 | subject relationship context ] and also has an association to a specific subject. For example, if the concept [ 160303001 | FH: diabetes mellitus ] is stated in an observation linked to a person other than the subject of the record, this could mean either (a) "the patient has a family history of diabetes, in the named family member" or (b) "the identified subject has a family history of diabetes".
Specific recommendations on this should be included in communication specifications. Where a communication pertains to an individual patient interpretation (a) is recommended. However, specific instances of the subject participation in a communication about a group of patients may need to specify interpretation (b).