COVID-19 FHIR Profile Library IG Informative Version
1.0.0 - Informative US

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## Extension: COVID19UnderlyingConditionReference - Detailed Descriptions

Active as of 2022-07-25

Definitions for the covid19-underlying-condition-reference extension.

1. Extension
Definition | An extension to capture the referred-to condition resource for the underlying condition to COVID-19
Control | 0..* This element is affected by the following invariants: ele-1
Invariants | Defined on this element ele-1: All FHIR elements must have a @value or children (: hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (: extension.exists() != value.exists())
2. Extension.id
Definition | Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
Control | 0..1
Type | string
3. Extension.extension
Definition | An Extension
Control | 0..0
Type | Extension
Invariants | Defined on this element ele-1: All FHIR elements must have a @value or children (: hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (: extension.exists() != value.exists())
Slicing | This element introduces a set of slices on Extension.extension. The slices are unordered and Open, and can be differentiated using the following discriminators: value @ url
4. Extension.url
Definition | Source of the definition for the extension code - a logical name or a URL.
Control | 1..1
Type | uri
Comments | The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Fixed Value | http://hl7.org/fhir/us/covid19library/StructureDefinition/covid19-underlying-condition-reference
5. Extension.value[x]
Definition | Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
Control | 0..1
Type | Reference
[x] Note | See Choice of Data Types for further information about how to use [x]
Invariants | Defined on this element ele-1: All FHIR elements must have a @value or children (: hasValue() or (children().count() > id.count()))