FHIR Chat · extension on choice data type

Stream: implementers

Topic: extension on choice data type

Yunwei Wang (Jun 22 2021 at 19:01):

How do I add extension to an element having choice data type. For example: how do I add DAR extension to Condition.onset (in JSON)?

Eric Haas (Jun 23 2021 at 04:48):

{
  "resourceType": "Condition",
  "id": "example",
  "meta": {
    "profile": [
      "http://hl7.org/fhir/us/core/StructureDefinition/us-core-condition"
    ]
  },
  "clinicalStatus": {
    "coding": [
      {
        "system": "http://terminology.hl7.org/CodeSystem/condition-clinical",
        "code": "active",
        "display": "Active"
      }
    ],
    "text": "Active"
  },
  "verificationStatus": {
    "coding": [
      {
        "system": "http://terminology.hl7.org/CodeSystem/condition-ver-status",
        "code": "confirmed",
        "display": "Confirmed"
      }
    ],
    "text": "Confirmed"
  },
  "category": [
    {
      "coding": [
        {
          "system": "http://terminology.hl7.org/CodeSystem/condition-category",
          "code": "problem-list-item",
          "display": "Problem List Item"
        }
      ],
      "text": "Problem"
    }
  ],
  "code": {
    "text": "Single liveborn, born in hospital"
  },
  "subject": {
    "display": "Amy V. Shaw"
  },
  "_onsetDateTime": {
    "extension": [
      {
        "url": "http://hl7.org/fhir/StructureDefinition/data-absent-reason",
        "valueCode": "unknown"
      }
    ]
  }
}

Eric Haas (Jun 23 2021 at 04:51):

JSON representation of primitive elements

Yunwei Wang (Jun 23 2021 at 14:28):

@Eric Haas But the interpretation of this is "I don't know the onsetDateTime". How do I say "I don't know any of the onset, no matter it is onsetDatetime, or onsetPeriod, or onsetAge". Do I need to list all the choices like

  "_onsetDateTime": {
    "extension": [
      {
        "url": "http://hl7.org/fhir/StructureDefinition/data-absent-reason",
        "valueCode": "unknown"
      }
    ]
  },
  "_onsetAge": {
    "extension": [
      {
        "url": "http://hl7.org/fhir/StructureDefinition/data-absent-reason",
        "valueCode": "unknown"
      }
    ]
  }
...

Eric Haas (Jun 23 2021 at 14:57):

good question, but note that if you knew the time and the Age you would only report one.

Eric Haas (Jun 23 2021 at 14:58):

and no you would not list them as above since max=1

Eric Haas (Jun 23 2021 at 15:01):

what you are really asking for is:

"_onset[x]": {
"extension": [
{
"url": "http://hl7.org/fhir/StructureDefinition/data-absent-reason",
"valueCode": "unknown"
}
]
},

which I think would be really confusing for implementers since onset[x] doesn't exist over the wire

Eric Haas (Jun 23 2021 at 15:04):

so if the element is min=0 it is omitted. I assume what you are asking is if the min=1

Yunwei Wang (Jun 24 2021 at 13:43):

Yes. I agree that using _onset[x] is confusing. So I think the current consensus is that I can pick any one of the choice and add DAR there.

Eric Haas (Jun 24 2021 at 15:56):

do you think we should document that.

Yunwei Wang (Jun 25 2021 at 14:42):

I think we should document at least in DAR extension. I don't know if other extension could have similar confusion.

Lloyd McKenzie (Jun 25 2021 at 16:03):

You have to pick a type. You can't say "I don't know independent of type" because every instance must have a specific type.

Yunwei Wang (Jun 25 2021 at 17:06):

In US Core, the US Core DiagnosticReport Lab profile has a mandatory sliced element DiagnosticReport.effective image.png. So if I want to use DAR on that element, I have to pick one of the concrete type, either effectiveDateTime or effectivePeriod, to apply DAR extension. Is my understanding correct?

Lloyd McKenzie (Jun 25 2021 at 21:06):

Correct

Last updated: Apr 12 2022 at 19:14 UTC

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FHIR Chat · extension on choice data type · implementers