it seems a quite basic question, but I am still not clear what's the best practice in industry.
As you know, in both Dicom and HL7, patient has id and issuer, ( or assigning authority in HL7)
for example, in HL7 PID3 ,
subcomponents of assigning authority : &&
In FHIR, patient has identifier , so quite straightforward, we can use the identifier's value to represent the patient id.
for issuer, we first wanted to use system to represent, it also looks quite handy, because we have a very common user case that search patient via patient id + issuer, then we can use issuer|id to search, like NHS|PA12345
unfortunately, this violate FHIR'S constraints, because the system is an uri, here it need to be a full url or a string start with 'urn'.
One of the possible solution is we declare system as below
but what if we also want to support universal ID and universal ID type code
wondering the constraint to system under Identifier, is it too strict?
and what's best practice for patient id handing in FHIR?
Thanks in advance.