FHIR Observations derived from questionnaire responses

Question

I want to create an Observation derived from a QuestionnaireResponse. What is the convention for pointing to a specific item in a QuestionnaireResponse object from which the Observation was derived? I was thinking you could point at the QuestionnaireResponse object and then refer to a linkId (or even the linkId of a nested item).

E.g.

QuestionnaireResponse = {
  "id": "QR1",
  "item": [
    {
      "linkId": "I1",
      ..
    }
  ],
  ..
}

The Observation derivedFrom the questionnaire response in "I1" would be

{
  "derivedFrom": [
    "type": ?,
    "reference": ?
  ],
  ..
}

Answer 1

At the moment, there's no standard way to point to the specific 'item' within the QuestionnaireResponse, just the response itself. We've approved a proposal in R5 to add an extension to Reference that would allow you to refer to a specific 'id' within the QuestionnaireResponse - though that would mean the relevant item would need to have an id.