When a third party may be providing conditions that have been detected, as well as questionnaires that a practitioner may use regarding the condition, how would you make the connection between the two? From looking at the specs, it doesn’t appear that there’s a direct way of associating these (it would have to be from Condition to Questionnaire, since Condition is patient-specific). IQuestionnaire has a “useContext” property which can have a CodeableConcept, which could be used to match against the Condition Category Codes in Condition.category, except that useContext isn’t a specified search parameter for Questionnaire… Thoughts on how you’d do this?
At the moment, it looks like you’d need an extension. However, it sounds like this might be a common enough use-case for HL7 to at least consider a common extension or perhaps a core element - something like the “supportingInfo” found on other resources. You might want to submit a change request to get that conversation started.