A common type of Care Gap or Outcome groups track are based on an event that then requires follow up. One term I have heard for these are Episodic based measures so I will refer to them as such. Medication Reconciliation Post-Discharge is one such measure. For these measures it is important to know the underlying date that the event happened (in the example this will be the discharge). That will allow groups that to know how actionable the gap is or if it is more informational. 

Suggested Solution: Add an extension to allow sending an Anchor Encounter Date that is used when the care gaps is for an Episodic based measure.

• Anchor Encounter Date: For episodic-based measures, this is the date of the encounter the qualifying event occurred for the measure outcome.  

Alternate Solution: Today we could link to the encounter in evaluatedResource (Using MeasureReport.evaluatedResource.extension-populationReference as well). However I worry that not all groups using this will be able to give us robust encounter references depending on capabilities of their Outcome Calculation system and Clinical Data repositories.