<status value="active"/> <date value="2014-03-26"/> <description value="Indicates the result of a particular allergy test. E.g. Negative, Mild, Moderate, Severe"/> <compose> <include> <system value="http://terminology.hl7.org/CodeSystem/v3-ObservationValue"/> <filter> <property value="concept"/> <op value="is-a"/> <value value="_AllergyTestValue"/> </filter> </include> </compose> </ValueSet>