Support Continuous-Variable measure scoring using Measure Observation aggregation

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This is a feature request to implement 'Continuous-Variable' measure scoring using Measure Observation aggregation

Continuous variable measure scoring is defined in QM IG to allow for use of measure-observation defined function pointed at results of the 'measure-population' and a specific aggregation method to calculate measure score. Use the shared link to review more specifics of the standard.

The way to define a Measure Observation in a Measure resource is to have the following required fields:

• extension: criteria reference- this is used to specify the population.id of the measure.group that holds the input parameter values that are evaluated
• criteria: which is the CQL function used to generate Quantity based values for aggregation
• extension: aggregate method- this is the type of aggregation performed on the generated results from the function

Example Measure Observation as defined in Measure Resource

{
  "extension": [
    {
      "url": "http://hl7.org/fhir/us/cqfmeasures/StructureDefinition/cqfm-criteriaReference",
      "valueString": "measure-population-identifier"
    },
    {
      "url": "http://hl7.org/fhir/us/cqfmeasures/StructureDefinition/cqfm-aggregateMethod",
      "valueCode": "median"
    }
  ],
  "identifier": {
    "value": "measure-observation-identifier"
  },
  "code": {
    "coding": [
      {
        "code": "measure-observation"
      }
    ]
  },
  "criteria": "\"Measure Observation\""
}

Example Measure Report

{
  "resourceType": "MeasureReport",
  "id": "cv-summary",
  "status": "complete",
  "type": "summary",
  "measure": "http://example.org/fhir/Measure/avg-length-of-stay",
  "period": {
    "start": "2025-01-01",
    "end": "2025-06-30"
  },
  "group": [
    {
      "id": "length-of-stay",
      "population": [
        {
          "id": "ip",
          "code": {
            "coding": [
              {
                "system": "http://terminology.hl7.org/CodeSystem/measure-population",
                "code": "initial-population",
                "display": "Initial Population"
              }
            ]
          },
          "count": 120
        },
        {
          "id": "mp",
          "code": {
            "coding": [
              {
                "system": "http://terminology.hl7.org/CodeSystem/measure-population",
                "code": "measure-population",
                "display": "Measure Population"
              }
            ]
          },
          "count": 118
        },
        {
          "id": "mpe",
          "code": {
            "coding": [
              {
                "system": "http://terminology.hl7.org/CodeSystem/measure-population",
                "code": "measure-population-exclusion",
                "display": "Measure Population Exclusion"
              }
            ]
          },
          "count": 2
        },
        {
          "id": "mo",
          "code": {
            "coding": [
              {
                "system": "http://terminology.hl7.org/CodeSystem/measure-population",
                "code": "measure-observation",
                "display": "Measure Observation"
              }
            ]
          },
          "extension": [
            {
              "url": "http://hl7.org/fhir/us/cqfmeasures/StructureDefinition/cqfm-aggregateMethod",
              "valueCodeableConcept": {
                "text": "avg"
              }
            }
          ],
          "count": 118
        }
      ],
      "measureScore": {
        "value": 5.2
      }
    }
  ]
}

aggregate methods to implement

• sum, max, min, avg, count, median

rules assumptions

• population defined extensions should display on produced measure report (aggregate method) to assist with readability
• given measureObservation currently only outputs to group score, only one measureObservation can be specified per group. If multiple need to be exposed, it will have to be in a different group. Example: aggregate avg in group1, max group2...etc
• units are not seeded as part of this feature