Stream: IG creation
Topic: data-absent-reason extension vs "nullFlavor"s in value set
Sarah Gaunt (Nov 12 2021 at 00:23):
We (@David deRoode) are wondering what current best practice is around using the data-absent-reason extension vs specifying "nullFlavor" type values in a value set? Are there cases where one would be better than another or is one way always preferred?
Eric Haas (Nov 12 2021 at 00:39):
Sarah Gaunt said:
We (David deRoode) are wondering what current best practice is around using the data-absent-reason extension vs specifying "nullFlavor" type values in a value set? Are there cases where one would be better than another or is one way always preferred?
Bottom line is to use codes instead of DAR for coded elements:
see http://hl7.org/fhir/us/core/general-guidance.html#missing-data
We got our hands slapped for originally trying to DAR coded elements, because you can't use an extension for extensible and required bindings for min=1 coded elements - the bindings prohibit a DAR work-around. Besides it makes more sense to express the DAR concept as a code in element itself. You are screwed if you have a min=1
and required binding and no code available. ( Had trackers to make this guidance more explicit and obvious, but I don't think it has been applied yet - need to follow up on that)
Sarah Gaunt (Nov 12 2021 at 02:41):
Eric Haas said:
We got our hands slapped for originally trying to DAR coded elements, because you can't use an extension for extensible and required bindings for min=1 coded elements - the bindings prohibit a DAR work-around. Besides it makes more sense to express the DAR concept as a code in element itself. You are screwed if you have a min=1
and required binding and no code available. ( Had trackers to make this guidance more explicit and obvious, but I don't think it has been applied yet - need to follow up on that)
Yikes - thinking I might have done that in a few places... Better go and check.
Frank Oemig (Nov 13 2021 at 09:02):
What about creating value sets that include the null-flavour codesystem?
Lloyd McKenzie (Nov 14 2021 at 20:06):
@Frank Oemig That's what's recommended. Though we generally encourage people to draw on the DAR code system rather than the null flavor code system.
Last updated: Apr 12 2022 at 19:14 UTC
