description: This extension links this observation with the certified reference material used for the calibration.\nThe certified reference material is identified by using a CodeableConcept.\nThis extension should be used when the unit is UCUM [IU]. package_name: hl7.fhir.eu.laboratory derivation: constraint name: ObservationCertifiedRefMaterialCodeable type: Extension elements: extension: {index: 0} url: pattern: {type: Uri, value: 'http://hl7.eu/fhir/laboratory/StructureDefinition/observation-certifiedRefMaterialCodeable'} index: 1 value: choices: [valueCodeableConcept] index: 3 valueCodeableConcept: {type: CodeableConcept, choiceOf: value, index: 4} package_version: 2.0.0 extensions: {} class: extension kind: complex-type url: http://hl7.eu/fhir/laboratory/StructureDefinition/observation-certifiedRefMaterialCodeable base: http://hl7.org/fhir/StructureDefinition/Extension version: 2.0.0