This structure is based on the Patient Care Concern act, which went through "Harmonization" (The RIM modification process) in 2005/2006, but probably finished being implemented properly in the RIM sometime in 2010 or thereabouts (due to administrative rather than technical issues, and mostly dropped balls on the administrative side).
The Concern Act that the Patient Care Workgroup developed has a great deal of capability. Current "concerns" among CCDA implementers and HL7 developers is that it is overkill for many uses, e.g., handling allergy lists.
Back in the day (2006) when it was first added to a CDA Implementation Guide (the IHE PCC Technical Framework was first to adopt it), the rationale for including it was to address two issues:
- Tracking who added the item to the current (allergies or problems) list.
- Tracking when it was added or removed.
Several have noted that this information also appears in audit logs, which is certainly a true statement. However, audit logs are not information items that are typically made available to normal users.
These two pieces of data have clinical significance. The who tells you who added (or removed) the item from the list, so you can track down what happened. This may be distinct from who made the observation (e.g., a DX of a disease may have come from another provider).
The question arose from Grahame's work on supporting CCDA capabilities in FHIR. In looking through FHIR, there are two Resources of interest for Concern. One is Condition, and the other is AllergyIntollerance.
In examining these two resources, they both support capture of "who recorded" the information and when, in the Condition case, called the Asserter, and in the Allergy case, the Recorder. Condition also includes onset and abatement dates. So it already has the necessary components needed to support the capabilities of Concern that are used in the wild to MY knowledge. The allergy case is missing the onset/abatement dates, likely because of the [mistaken in my opinion] assumption that this is either not important, or that allergies never go away (Never and always are two dangerous words to use in Healthcare or in any other endeavor). I can live without this capability in allergies because it can be added back through the extension mechanism.
So, to handle what is needed for CCDA in FHIR, applying the 80/20 rule, I'd just use Condition and AllergyIntollerance, and push all the concern pieces NOT present into extension.
NOTE: In CDA and elsewhere in HL7 Version 3, Allergy is treated simply as a specialization of problem. While this makes sense to engineers, it makes little sense to many physicians. This is in part why Concern is used in both places, but also because it supports the capture of information not found in Observation.