Supplemental Metadata

The purpose of FHIR is to enable the interoperability of healthcare data so that all systems send and receive data in a standardised way. In general, this will include high level pieces of information on a patients history such as a medication they were prescribed. FHIR is not, however, expected to include every piece of metadata associated with a concept that appears in the patient history.

An example of this would be the associated metadata or hierarchical neighbourhood that accompanies SNOMED-CT or dm+d codes. It would be expected that on the presentation of such codes to refer to external sources that provide a full catalogue of these code systems. The metadata associated with these concepts can then be read as required.

Another consideration is that certain metadata needs to be curated and is in a constant state of flux. Including this within the profile rather than referring to an external source may make the data out of date and difficult to maintain. While FHIR profiles could contain this information they would require constant updates to ensure they currently have valid values. An example of this would be if a medication is on a formulary and then removed. If this information was included on all records where this medication was dispensed then an update transaction would need to occur. Therefore to prevent such occurrences the metadata should be excluded from the profile and an external reference made to find the current status/value. The external resource should have a full history which can be pooled to find out information in a given time frame (e.g. this drug was on the formulary between X and Y dates but not after Z date).