“We should only use FHIR resource types that are normative.”
I’ve heard this many times, usually from project leaders new to FHIR.
The trigger for this conversation is often the FHIR documentation itself. The new project lead will spend some time reading up on FHIR, paying particular attention to the resource types used in the project — as they should.
They end up in the FHIR documentation for a common resource type such as Condition where they meet the TU flag for the first time.
TU = TRIAL USE.
The capitalization is mine. I’m using it to illustrate how this looks and sounds to a technically aware but FHIR unaware project lead.
They dig a little deeper into the documentation, keen to understand what Trial Use really means. The explanation does not ease their minds.
Future versions of FHIR may make significant changes to Trial Use content that are not compatible with previously published content.
An emergency meeting with the project’s technical leads at this point is not uncommon.
At these meetings we talk about FHIR R4, what maturity levels mean, and how the project will not be migrating to R5 or even R6 any time in the next five years — if ever.
We might also discuss US regulations mandating the use of FHIR R4 and how the NHS in the UK is fully invested in R4.
There are 145 resource types in FHIR R4. Only 13 of them are “normative”. The rest are all designated “Trial Use”.
FHIR itself is a long way from being normative. But that doesn’t mean you cannot or should not use it. Or that you cannot or should not use specific resource types.
Once you commit to a FHIR version (R4 or R5), you should feel confident using all resource types in that version, irrespective of their maturity level.
Having said all that, the FHIR documentation could do with a big DON’T PANIC button next to the description of “Trial Use”.
More about FHIR stability and maturity levels: https://hl7.org/fhir/R4/versions.html#std-process
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