Related Persons
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This page discusses the manner in which FHIR RelatedPerson resources are handled and the various caveats of how those relate to the iCDR relationships.
The CDR storage model support robust linkages between patients and persons. Some SanteDB services such as the Immunization Management Service (IMS) represent relationships between non-patient persons as a direct relationship between an instance of a Patient entity and a Person entity with a relationship type.
This example illustrates a simple non-patient entity (Sarah Smith) is the mother of a Patient (Baby Joe Smith).
Additionally, the CDR also supports the direct linking of patient entities to other patient entities in relationships. The illustration below illustrates a patient entity (Sarah Smith) is the mother of Patient (Baby Joe Smith).
This relationship works because in SanteDB a Patient is a Person.
In FHIR, the RelatedPerson resource is used to represent a related person. Unlike SanteDB's RIM model, FHIR's RelatedPerson maps to one of the following internal concepts in SanteDB:
A combination of Person and EntityRelationship where the Person may only contain one relationship to one Patient, or
An EntityRelationship only, where only the relationship type is expressed.
A RelatedPerson represents a combination of Personand EntityRelationship when it is expressed as:
This condition is described in the section Simple Relationships on this page. However, a RelatedPerson is only an EntityRelationship when it is represented as:
The behavior of the iCDR is described in Complex Relationships in this page.
The manner in which HL7 FHIR views patient relationships is reversed from the CDR's view of relationships. Primarily, HL7 FHIR would represent a non-patient person relationship to a patient as.
In effect, the FHIR resource RelatedPerson is a mashup of a Person and an EntityRelationship, as the RelatedPerson contains elements of both objects.
The CDR handles these relationship types automatically. When querying from FHIR with _revInclude=RelatedPerson:patient , the CDR will interpret either of these relationships and will construct the appropriate response messages for broadcasts and searches.
The CDR will treat the target of the personal relationship as a Person. Since the CDR support hierarchy and Patient is a Patient, this translation is transparent to the FHIR interface. The CDR treats the instance of RelatedPerson as the EntityRelationship instance between the two entities. The CDR's FHIR plugin will reverse the relationship to ensure that the FHIR RelatedPerson references is correctly associated.
This behaviour matches the HL7 processor when an NK1 segment is present. For example, this HL7 message
And this FHIR message
Will both result in this structure in the database.
Relationships between Patients in FHIR are slightly more complex, take for example, a scenario where a Sarah Smith is a patient and is related to Baby Joe Smith. In FHIR the structure of this message would be as follows.
The HL7 FHIR processor on a read will not reproduce this when a patient is read from the database and is directly related to another patient. Instead the simple case of representation is performed on a query.
When creating or updating a related person in this manner the following structure is created in the RIM structure.
This structure is also created from the HL7v2 process when an NK1 segment points at a previously registered PID segment. For example, the following HL7v2 structure also creates a similar structure as the FHIR interface.
This structure will indicate that a patient is admitted to hospital (Sarah Smith) and then is linked to Baby Joe Smith as a next of kin. In FHIR this structure is represented as.
When querying a patient which has a relationship with another patient (for example, querying for ?identifier=HL7-3 ) you can use _revInclude=RelatedPerson:patient to join a RelatedPerson instance, however the included RelatedPerson instance will be represented as a simple relationship rather than a complex relationship.
It is not possible to perform a _revInclude=Patient:link on order to retrieve patient information about the RelatedPerson , this is because there is no relationship or link per-se between the Person and Patient, in SanteDB they are the same resource
The id and fullUrl of the RelatedPerson is the id property of the EntityRelationship rather than the Person. This is because in FHIR a RelatedPerson can have exactly one relationship to exactly one Patient, however in SanteDB RIM a Person can have infinite relationships to infinite Patient resources.
When querying directly for a Patient instance on the FHIR interface, you may see one or more link properties such as listed below, this link information is provided to indicate there exists a relationship where the patient is a target of a relationship.
