{
  "resourceType": "Questionnaire",
  "status": "active",
  "item": [
    {
      "linkId": "kidney",
      "text": "Kidney Function",
      "type": "group",
      "item": [
        {
          "linkId": "kidney-age",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "30525-0"
            }
          ],
          "text": "Age (years)",
          "type": "integer",
          "extension": [
            {
              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-unit",
              "valueCoding": {
                "system": "http://unitsofmeasure.org",
                "code": "a",
                "display": "years"
              }
            }
          ]
        },
        {
          "linkId": "kidney-sex",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "76689-9"
            }
          ],
          "text": "Sex assigned at birth (used by both formulas)",
          "type": "choice",
          "extension": [
            {
              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-itemControl",
              "valueCodeableConcept": {
                "coding": [
                  {
                    "system": "http://hl7.org/fhir/questionnaire-item-control",
                    "code": "radio-button"
                  }
                ]
              }
            }
          ],
          "answerOption": [
            {
              "valueCoding": {
                "system": "http://loinc.org",
                "code": "LA3-6",
                "display": "Female"
              }
            },
            {
              "valueCoding": {
                "system": "http://loinc.org",
                "code": "LA2-8",
                "display": "Male"
              }
            }
          ]
        },
        {
          "linkId": "kidney-weight",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "29463-7"
            }
          ],
          "text": "Weight (kg)",
          "type": "decimal",
          "extension": [
            {
              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-unit",
              "valueCoding": {
                "system": "http://unitsofmeasure.org",
                "code": "kg",
                "display": "kg"
              }
            }
          ]
        },
        {
          "linkId": "kidney-creatinine",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "2160-0"
            }
          ],
          "text": "Serum creatinine (mg/dL)",
          "type": "decimal",
          "extension": [
            {
              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-unit",
              "valueCoding": {
                "system": "http://unitsofmeasure.org",
                "code": "mg/dL",
                "display": "mg/dL"
              }
            }
          ]
        },
        {
          "linkId": "kidney-egfr",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "98979-8"
            }
          ],
          "text": "eGFR (mL/min/1.73 m², CKD-EPI 2021)",
          "type": "decimal",
          "readOnly": true,
          "extension": [
            {
              "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-calculatedExpression",
              "valueExpression": {
                "language": "text/fhirpath",
                "expression": "iif((%resource.item.where(linkId='kidney').item.where(linkId='kidney-creatinine').answer.valueDecimal) > 0 and (%resource.item.where(linkId='kidney').item.where(linkId='kidney-age').answer.valueInteger).exists() and (%resource.item.where(linkId='kidney').item.where(linkId='kidney-sex').answer.valueCoding.code).exists(), (142 * iif(((%resource.item.where(linkId='kidney').item.where(linkId='kidney-creatinine').answer.valueDecimal) / iif(((%resource.item.where(linkId='kidney').item.where(linkId='kidney-sex').answer.valueCoding.code) = 'LA3-6'), 0.7, 0.9)) < 1, ((%resource.item.where(linkId='kidney').item.where(linkId='kidney-creatinine').answer.valueDecimal) / iif(((%resource.item.where(linkId='kidney').item.where(linkId='kidney-sex').answer.valueCoding.code) = 'LA3-6'), 0.7, 0.9)), 1).power(iif(((%resource.item.where(linkId='kidney').item.where(linkId='kidney-sex').answer.valueCoding.code) = 'LA3-6'), -0.241, -0.302)) * iif(((%resource.item.where(linkId='kidney').item.where(linkId='kidney-creatinine').answer.valueDecimal) / iif(((%resource.item.where(linkId='kidney').item.where(linkId='kidney-sex').answer.valueCoding.code) = 'LA3-6'), 0.7, 0.9)) > 1, ((%resource.item.where(linkId='kidney').item.where(linkId='kidney-creatinine').answer.valueDecimal) / iif(((%resource.item.where(linkId='kidney').item.where(linkId='kidney-sex').answer.valueCoding.code) = 'LA3-6'), 0.7, 0.9)), 1).power(-1.2) * 0.9938.power((%resource.item.where(linkId='kidney').item.where(linkId='kidney-age').answer.valueInteger)) * iif(((%resource.item.where(linkId='kidney').item.where(linkId='kidney-sex').answer.valueCoding.code) = 'LA3-6'), 1.012, 1)).round(0), {})"
              }
            }
          ]
        },
        {
          "linkId": "kidney-crcl",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "35591-7"
            }
          ],
          "text": "Creatinine clearance (mL/min, Cockcroft–Gault)",
          "type": "decimal",
          "readOnly": true,
          "extension": [
            {
              "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-calculatedExpression",
              "valueExpression": {
                "language": "text/fhirpath",
                "expression": "iif((%resource.item.where(linkId='kidney').item.where(linkId='kidney-sex').answer.valueCoding.code).exists(), ((((140 - (%resource.item.where(linkId='kidney').item.where(linkId='kidney-age').answer.valueInteger)) * (%resource.item.where(linkId='kidney').item.where(linkId='kidney-weight').answer.valueDecimal)) / (72 * (%resource.item.where(linkId='kidney').item.where(linkId='kidney-creatinine').answer.valueDecimal))) * iif((%resource.item.where(linkId='kidney').item.where(linkId='kidney-sex').answer.valueCoding.code) = 'LA3-6', 0.85, 1)).round(0), {}).where($this >= 0)"
              }
            }
          ]
        }
      ]
    }
  ]
}