http://hl7.org/fhir/StructureDefinition/observation-delta|4.0.1

The qualitative change in the value relative to the previous measurement. Usually only recorded if the change is clinically significant.
typedestination
baseDefinitionhttp://hl7.org/fhir/StructureDefinition/Extension
typehttp://hl7.org/fhir/StructureDefinition/Extension
Extension.value[x].typehttp://hl7.org/fhir/StructureDefinition/CodeableConcept