Quality Measure Implementation Guide
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## Extension: CQM Population Basis

Official URL: http://hl7.org/fhir/uv/cqm/StructureDefinition/cqm-populationBasis | Version: 1.0.0 | Highlight text changes?
Standards status: Trial-use Active as of 2026-04-07 | Maturity Level: 4 | Computable Name: CQMPopulationBasis
Other Identifiers: OID:2.16.840.1.113883.4.642.40.61.42.21

The population basis specifies the type of elements in the population. For a subject-based measure, this is boolean (because the subject and the population basis are the same, and the population criteria define yes/no values for each individual in the population). For measures that have a population basis that is different than the subject, this element specifies the type of the population basis. For example, an encounter-based measure has a subject of Patient and a population basis of Encounter, and the population criteria all return lists of Encounters. Note that the subject of a measure can be found in the element subject[x].

Context of Use

This extension may be used on the following element(s)

- Element ID: `Measure`
- Element ID: `Measure.group`
- Element ID: `Measure.group.population`

Usage info

Usages:

- Use this Extension: CQM Computable Measure and CQM Ratio Measure
- Examples for this Extension: Bundle/EmergencyCapacityReportingExample, BCSComponent, BedCapacityMeasureDaily, BedCapacityMeasureMonthly... Show 19 more, CAUTIRateExample, CAUTISIRExample, CCSComponent, EXM108, EXM124, EXM125, EXM130, EXM146, EXM55, MeasureEXM, EXMRatioMeasure, HBPComponent, MultiRateExample, PVSComponent, SupportingEvidenceExample, TSCComponent, Terminology_FHIR, MeasureAgeStratifiedExample and PublishableMeasureEXM

You can also check for usages in the FHIR IG Statistics

### Formal Views of Extension Content

Description Differentials, Snapshots, and other representations.

- Differential Table
- Snapshot Table
- Statistics/References
- All

Name | Flags | Card. | Type | Description & Constraints Filter: Bindings Constraints Obligations
--- | --- | --- | --- | ---
Extension | C | 0..* | Extension | What type of population Constraints: popBasis-1
url |  | 1..1 | uri | "http://hl7.org/fhir/uv/cqm/StructureDefinition/cqm-populationBasis"
value[x] |  | 0..1 |  | Value of extension Binding: FHIRAllTypes (required): The type of elements in the population
valueCode |  |  | code |
valueDataRequirement |  |  | DataRequirement |
Documentation for this format

#### Terminology Bindings (Differential)

Path | Status | Usage | ValueSet | Version | Source
Extension.value[x] | Base | required | FHIRAllTypes | 📦4.0.1 | FHIR Std.

#### Constraints

Id | Grade | Path(s) | Description | Expression
popBasis-1 | error | Extension | If DataRequirement.type is present, it may only contain the elements 'profile' and 'codeFilter'. | `value.exists() and value.is(DataRequirement) implies ( value.as(DataRequirement).type.exists() and value.as(DataRequirement).limit.empty() and value.as(DataRequirement).sort.empty() and value.as(DataRequirement).dateFilter.empty() and value.as(DataRequirement).subject.empty() and value.as(DataRequirement).mustSupport.empty())`

Name | Flags | Card. | Type | Description & Constraints Filter: Bindings Constraints Obligations
--- | --- | --- | --- | ---
Extension | C | 0..* | Extension | What type of population Constraints: popBasis-1
id |  | 0..1 | string | Unique id for inter-element referencing
extension |  | 0..* | Extension | Additional content defined by implementations Slice: Unordered, Open by value:url
url |  | 1..1 | uri | "http://hl7.org/fhir/uv/cqm/StructureDefinition/cqm-populationBasis"
value[x] |  | 0..1 |  | Value of extension Binding: FHIRAllTypes (required): The type of elements in the population
valueCode |  |  | code |
valueDataRequirement |  |  | DataRequirement |
Documentation for this format

#### Terminology Bindings

Path | Status | Usage | ValueSet | Version | Source
Extension.value[x] | Base | required | FHIRAllTypes | 📦4.0.1 | FHIR Std.

#### Constraints

Id | Grade | Path(s) | Description | Expression
ele-1 | error | **ALL** elements | All FHIR elements must have a @value or children | `hasValue() or (children().count() > id.count())`
ext-1 | error | **ALL** extensions | Must have either extensions or value[x], not both | `extension.exists() != value.exists()`
popBasis-1 | error | Extension | If DataRequirement.type is present, it may only contain the elements 'profile' and 'codeFilter'. | `value.exists() and value.is(DataRequirement) implies ( value.as(DataRequirement).type.exists() and value.as(DataRequirement).limit.empty() and value.as(DataRequirement).sort.empty() and value.as(DataRequirement).dateFilter.empty() and value.as(DataRequirement).subject.empty() and value.as(DataRequirement).mustSupport.empty())`

Summary

Simple Extension with the type code, DataRequirement: The population basis specifies the type of elements in the population. For a subject-based measure, this is boolean (because the subject and the population basis are the same, and the population criteria define yes/no values for each individual in the population). For measures that have a population basis that is different than the subject, this element specifies the type of the population basis. For example, an encounter-based measure has a subject of Patient and a population basis of Encounter, and the population criteria all return lists of Encounters. Note that the subject of a measure can be found in the element subject[x].

Maturity: 4

Differential ViewDifferential View

Name | Flags | Card. | Type | Description & Constraints Filter: Bindings Constraints Obligations
--- | --- | --- | --- | ---
Extension | C | 0..* | Extension | What type of population Constraints: popBasis-1
url |  | 1..1 | uri | "http://hl7.org/fhir/uv/cqm/StructureDefinition/cqm-populationBasis"
value[x] |  | 0..1 |  | Value of extension Binding: FHIRAllTypes (required): The type of elements in the population
valueCode |  |  | code |
valueDataRequirement |  |  | DataRequirement |
Documentation for this format

#### Terminology Bindings (Differential)

Path | Status | Usage | ValueSet | Version | Source
Extension.value[x] | Base | required | FHIRAllTypes | 📦4.0.1 | FHIR Std.

#### Constraints

Id | Grade | Path(s) | Description | Expression
popBasis-1 | error | Extension | If DataRequirement.type is present, it may only contain the elements 'profile' and 'codeFilter'. | `value.exists() and value.is(DataRequirement) implies ( value.as(DataRequirement).type.exists() and value.as(DataRequirement).limit.empty() and value.as(DataRequirement).sort.empty() and value.as(DataRequirement).dateFilter.empty() and value.as(DataRequirement).subject.empty() and value.as(DataRequirement).mustSupport.empty())`

Snapshot View

Name | Flags | Card. | Type | Description & Constraints Filter: Bindings Constraints Obligations
--- | --- | --- | --- | ---
Extension | C | 0..* | Extension | What type of population Constraints: popBasis-1
id |  | 0..1 | string | Unique id for inter-element referencing
extension |  | 0..* | Extension | Additional content defined by implementations Slice: Unordered, Open by value:url
url |  | 1..1 | uri | "http://hl7.org/fhir/uv/cqm/StructureDefinition/cqm-populationBasis"
value[x] |  | 0..1 |  | Value of extension Binding: FHIRAllTypes (required): The type of elements in the population
valueCode |  |  | code |
valueDataRequirement |  |  | DataRequirement |
Documentation for this format

#### Terminology Bindings

Path | Status | Usage | ValueSet | Version | Source
Extension.value[x] | Base | required | FHIRAllTypes | 📦4.0.1 | FHIR Std.

#### Constraints

Id | Grade | Path(s) | Description | Expression
ele-1 | error | **ALL** elements | All FHIR elements must have a @value or children | `hasValue() or (children().count() > id.count())`
ext-1 | error | **ALL** extensions | Must have either extensions or value[x], not both | `extension.exists() != value.exists()`
popBasis-1 | error | Extension | If DataRequirement.type is present, it may only contain the elements 'profile' and 'codeFilter'. | `value.exists() and value.is(DataRequirement) implies ( value.as(DataRequirement).type.exists() and value.as(DataRequirement).limit.empty() and value.as(DataRequirement).sort.empty() and value.as(DataRequirement).dateFilter.empty() and value.as(DataRequirement).subject.empty() and value.as(DataRequirement).mustSupport.empty())`

Summary

Simple Extension with the type code, DataRequirement: The population basis specifies the type of elements in the population. For a subject-based measure, this is boolean (because the subject and the population basis are the same, and the population criteria define yes/no values for each individual in the population). For measures that have a population basis that is different than the subject, this element specifies the type of the population basis. For example, an encounter-based measure has a subject of Patient and a population basis of Encounter, and the population criteria all return lists of Encounters. Note that the subject of a measure can be found in the element subject[x].

Maturity: 4

Other representations of profile: CSV, Excel, Schematron