Comment:

I don't understand how common CQL libraries work, so hopefully this is a silly question. In the trivial example of patient age as a question backed by CQL. The CQL defines the data element as a LOINC code. I'd typically interpret that to mean that a SMART app would translate this LOINC code into a query on the Observation resource for the given patient. Is this true? Patient DOB is typically available on the FHIR Patient resource instead. I wouldn't expect age to be commonly associated with a LOINC code as an observation. Could you please clarify that somehow the DTR app or CQL libraries are smart enough to figure this out?

Summary:

Patient age as observation vs DOB on Patient resource.