The FHIR Clinical Reasoning Module defines the Measure resource and several associated operations. The Measure Resource represents a structured, computable definition of a health-related measure such as a clinical quality measure, public health indicator, or population analytics measure. These Measures can then be used for reporting, analytics, and data-exchange purposes.
Electronic Clinical Quality Measures (eCQMs) in FHIR are represented as a FHIR Measure resource containing metadata and terminology, a population criteria section, and at least one FHIR Library resource containing a data criteria section as well as the logic used to define the population criteria. The population criteria section typically contains initial population criteria, denominator criteria, and numerator criteria subcomponents, among others. This is elaborated upon in greater detail in the CQF Measures IG. An example of an eCQM as defined in FHIR looks like:
{
"resourceType" : "Measure",
"library" : [
"http://hl7.org/fhir/us/cqfmeasures/Library/EXMLogic"
],
"group" : [
{
"population" : [
{
"code" : {
"coding" : [
{
"code" : "initial-population"
}
]
},
"criteria" : {
"language" : "text/cql-identifier",
"expression" : "Initial Population"
}
},
{
"code" : {
"coding" : [
{
"code" : "numerator"
}
]
},
"criteria" : {
"language" : "text/cql-identifier",
"expression" : "Numerator"
}
},
{
"code" : {
"coding" : [
{
"code" : "denominator"
}
]
},
"criteria" : {
"language" : "text/cql-identifier",
"expression" : "Denominator"
}
}
]
}
]
}
Measures are then scored according the whether a subjects (or subjects) are members of the various populations.
For example, a Measure for Breast Cancer screening might define an Initial Population (via CQL expressions) of "all women", a Denominator of "women over 35", and a Numerator of "women over 35 who have had breast cancer screenings in the past year". If the Measure is evaluated against a population of 100 women, 50 are over 35, and of those 25 have had breast cancer screenings in the past year, the final score would be 50%1 (total number in numerator / total number in the denominator).
HAPI implements the $evaluate-measure operation. Support for additional operations is planned.
The $evaluate-measure
operation is used to execute a Measure as specified by the relevant FHIR Resources against a subject or set of subjects. This implementation currently focuses primarily on supporting the narrower evaluation requirements defined by the CQF Measures IG. Some support for extensions defined by other IGs is included as well, and the implementation aims to support a wider range of functionality in the future.
Several example Measures are available in the ecqm-content-r4 IG. Full Bundles with all the required supporting resources are available here. You can download a Bundle and load it on your server as a transaction:
POST http://your-server-base/fhir BreastCancerScreeningFHIR-bundle.json
These Bundles also include example Patient clinical data so once posted Measure evaluation can be invoked with:
GET http://your-server-base/fhir/Measure/BreastCancerScreeningFHIR/$evaluate-measure?periodStart=2019-01-01&periodEnd=2019-12-31&subject=numerator&reportType=subject
The FHIR Measure specification defines several types of Measures and various parameters for controlling the Measure evaluation. This section describes the features supported by HAPI.
The periodStart
and periodEnd
parameters are used to control the Reporting Period for which a report is generated. This corresponds to Measurement Period
defined in the CQL logic, as defined by the conformance requirements in the CQF Measures IG. Both periodStart
and periodEnd
must be used or neither must be used.
If neither are used the default reporting period specified in the CQL logic is used, as shown here
parameter "Measurement Period" Interval<DateTime>
default Interval[@2019-01-01T00:00:00.0, @2020-01-01T00:00:00.0)
If neither are used and there is no default reporting period in the CQL logic an error is thrown.
A request using periodStart
and periodEnd
looks like:
GET fhir/Measure/<MeasureId>/$evaluate-measure?periodStart=2019-01-01&periodEnd=2019-12-31
periodStart
and periodEnd
support Dates (YYYY, YYYY-MM, or YYYY-MM-DD) and DateTimes (YYYY-MM-DDThh:mm:ss+zz:zz)
Measure report types determine what data is returned from the evaluation. This is controlled with the reportType
parameter on the $evaluate-measure Operation
Report Type | Supported | Description |
---|---|---|
subject | Measure report for a single subject (e.g. one patient). Includes additional detail, such as evaluatedResources | |
subject-list | Measure report including the list of subjects in each population (e.g. all the patients in the "numerator") | |
population | Summary measure report for a population |
NOTE: There's an open issue on the FHIR specification to align these names to the MeasureReportType value set.
A request using reportType
looks like:
GET fhir/Measure/<MeasureId>/$evaluate-measure?reportType=subject-list
The subject of a measure evaluation is controlled with the subject
(R4+) and patient
(DSTU3) operation parameters. Currently, the only subject type supported by HAPI is Patient. This means that all Measure evaluation and reporting happens with respect to a Patient or set of Patient resources.
Subject Type | Supported | Description |
---|---|---|
Patient | A Patient | |
Practitioner | A Practitioner | |
Organization | An Organization | |
Location | A Location | |
Device | A Device | |
Group1 | A set of subjects |
A request using subject
looks like:
GET fhir/Measure/<MeasureId>/$evaluate-measure?subject=Patient/123
The set of Patients used for Measure evaluation is controlled with the subject
(R4+) or patient
(DSTU3), and practitioner
parameters. The two parameters are mutually exclusive.
Parameter | Supported | Description |
---|---|---|
Not specified | All Patients on the server | |
subject=XXX or subject=Patient/XXX | A single Patient | |
practitioner=XXX or practitioner=Practitioner/XXX | All Patients whose generalPractitioner is the referenced Practitioner | |
subject=Group/XXX 1 | A Group containing subjects | |
subject=XXX AND practitioner=XXX | Not a valid combination |
A request using practitioner
looks like:
GET fhir/Measure/<MeasureId>/$evaluate-measure?practitioner=Practitioner/XYZ
The following table shows the combinations of the subject
(or patient
), practitioner
and reportType
parameters that are valid
subject reportType | subject-list reportType | population reportType | |
---|---|---|---|
subject parameter | 1,2 | 1,2 | |
practitioner parameter | 3 |
subject
(or patient
) parameter to get report for multiple Patients. The subject-list and population report types have less detail than a subject report.subject
with a subject-list or population reportType
will be a valid combination once Group support is implemented.The Measure scoring method determines how a Measure score is calculated. It is set with the scoring element on the Measure resource.
The HAPI implementation conforms to the requirements defined by the CQF Measures IG. A more detailed description of each scoring method is linked in the table below.
Scoring Method | Supported | Description |
---|---|---|
proportion | Proportion Measures | |
ratio | Ratio Measures | |
continuous-variable | Continuous Variable | |
cohort | * | Cohort |
composite | See below |
An example Measure resource with scoring
defined looks like:
{
"resourceType": "Measure",
"scoring": {
"coding": [ {
"system": "http://terminology.hl7.org/CodeSystem/measure-scoring",
"code": "proportion",
"display": "Proportion"
} ]
}
}
A composite Measure is scored by combining and/or aggregating the results of other Measures. The compositeScoring element is used to control how composite Measures are scored. HAPI does not currently support any composite scoring method.
Composite Scoring Method | Supported | Description |
---|---|---|
opportunity | Combines Numerators and Denominators for each component Measure | |
all-or-nothing | Includes individuals that are in the numerator for all component Measures | |
linear | Gives an individual score based on the number of numerators in which they appear | |
weighted | Gives an individual a cored based on a weighted factor for each numerator in which they appear |
The HAPI implementation uses the populations defined by the CQF Measures IG for each scoring type. A matrix of the supported populations is shown in the Criteria Names section of the CQF Measures IG.
The logical criteria used for determining each Measure population is defined by the Measure.group.population.criteria element. The Measure specification allows population criteria to be defined using FHIR Path, CQL, or other languages as appropriate. The HAPI implementation currently only supports using CQL. The relationship between a Measure Population and CQL is illustrated in the Population Criteria section of the CQF Measures IG.
An example Measure resource with a population criteria referencing a CQL identifier looks like:
{
"resourceType": "Measure",
"group": [ {
"population": [ {
"code": {
"coding": [ {
"system": "http://terminology.hl7.org/CodeSystem/measure-population",
"code": "initial-population",
"display": "Initial Population"
} ]
},
"criteria": {
"language": "text/cql-identifier",
"expression": "Initial Population"
}
}]
}]
}
Expression Type | Supported |
---|---|
CQL | |
FHIR Path |
Supplemental Data Elements are used to report additional information about the subjects that may not be included in the Population criteria definitions. For example, it may be of interest to report the gender of all subjects for informational purposes. Supplemental data elements are defined by the Measure.supplementalData element, and are reported as Observations in the evaluatedResources of the MeasureReport.
Supplemental Data Elements can be specified as either CQL definitions or FHIR Path expressions.
Expression Type | Supported |
---|---|
CQL | |
FHIR Path |
An example Measure resource with some supplemental data elements set looks like:
{
"resourceType": "Measure",
"supplementalData": [ {
"code": {
"text": "sde-ethnicity"
},
"criteria": {
"language": "text/cql-identifier",
"expression": "SDE Ethnicity"
}
}]
}
Stratifiers are used divide Measure populations into segments of interest. For example, it may be of interest to compare the Measure score between different age groups or genders. Each stratum within a stratification is scored the same way as the overall population. Stratifiers are defined using the Measure.group.stratifier element.
An example Measure resource with a stratifier set looks like:
{
"resourceType": "Measure",
"group": [ {
"stratifier": [ {
"code": {
"text": "Stratum 1"
},
"criteria": {
"language": "text/cql-identifier",
"expression": "Stratification 1"
}
}]
}]
}
As with Populations and Supplemental Data Elements the criteria used for Stratification may be defined with CQL or FHIR Path.
Expression Type | Supported |
---|---|
CQL | |
FHIR Path |
The Measure specification also supports multidimensional stratification, for cases where more than one data element is needed.
Stratifier Type | Supported |
---|---|
Single Component | |
Multi Component |
A FHIR MeasureReport permits referencing the Resources used when evaluating in the MeasureReport.evaluatedResource element. HAPI includes these resources when generating subject
reports for a single Patient. Evaluated resources for population
or subject-list
reports are not included. For large populations this could quickly become an extremely large number of resources.
The evaluated resources will not include every resource on the HAPI server for a given subject. Rather, it includes only the resources that were retrieved from the server by the CQL logic that was evaluated. This corresponds to the data-requirements for a given Measure. As an example, consider the following CQL:
valueset "Example Value Set" : 'http://fhir.org/example-value-set'
define "Example Observations":
[Observation : "Example Value Set"]
That CQL will only select Observation Resources that have a code in the "Example Value Set". Those Observations will be reported in the Evaluated Resources while any others will not.
The lastReceivedOn
parameter is the date the Measure was evaluated and reported. It is used to limit the number of resources reported in the Measure report for individual reports. It is currently not supported by HAPI.
A number of extensions to Measure evaluation defined by various IGs are supported. They are described briefly in the table below.
Extension | Description |
---|---|
http://hl7.org/fhir/us/cqframework/cqfmeasures/StructureDefinition/cqfm-productLine | Used to evaluate different product lines (e.g. Medicare, Private, etc.) |
http://hl7.org/fhir/StructureDefinition/cqf-measureInfo | Used to denote a Measure Observation |
http://hl7.org/fhir/us/davinci-deqm/StructureDefinition/extension-populationReference | Used to specify the population that triggered a particular evaluatedResource |
There's not currently a way to configure which extensions are enabled. All supported extensions are always enabled.
Q: I get an error saying HAPI can't locate my library, and I've verified it's on the server.
A: HAPI follows the Library conformance requirements defined by the CQF Measures IG, meaning the Library must have a logic-library
type, the name and versions of the FHIR Library and CQL Library must match, and the url of the Library must end in the name of the Library.
FHIR Libraries generated from CQL via the IG Publisher follow these requirements automatically.
Q: Does HAPI support partitions for evaluation?
A: Yes, though the Measure and associated Resources must be in the same partition as the clinical data being used.
$data-requirements
, $collect-data
, $submit-data
, and $care-gaps
operations