http://hl7.org/fhir/StructureDefinition/flag-detail|4.0.1

Points to the Observation, AllergyIntolerance or other record that provides additional supporting information about this flag.
typedestination
baseDefinitionhttp://hl7.org/fhir/StructureDefinition/Extension
typehttp://hl7.org/fhir/StructureDefinition/Extension
Extension.value[x].typehttp://hl7.org/fhir/StructureDefinition/Reference
Extension.value[x].targetProfilehttp://hl7.org/fhir/StructureDefinition/Resource