description: Other preceding or concurrent observations that must be known to correctly interpret the the observation.  For example an fiO2 measure taken alongside of a SpO2 measurement.  See the [Observation notes](observation.html#notes) section for additional guidance.
package_name: hl7.fhir.core
derivation: constraint
name: precondition
type: Extension
elements:
  extension: {index: 0}
  url:
    type: uri
    pattern: {type: Uri, value: 'http://hl7.org/fhir/StructureDefinition/observation-precondition'}
    index: 1
  valueReference:
    type: Reference
    refers: ['http://hl7.org/fhir/StructureDefinition/Observation']
    index: 2
package_version: 3.5.0
extensions: {}
class: extension
kind: complex-type
url: http://hl7.org/fhir/StructureDefinition/observation-precondition
base: http://hl7.org/fhir/StructureDefinition/Extension
version: null