{
  "resourceType": "Questionnaire",
  "status": "active",
  "item": [
    {
      "linkId": "chem",
      "text": "Chemistry Calculations",
      "type": "group",
      "item": [
        {
          "linkId": "chem-na",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "2951-2"
            }
          ],
          "text": "Sodium (mmol/L)",
          "type": "decimal",
          "extension": [
            {
              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-unit",
              "valueCoding": {
                "system": "http://unitsofmeasure.org",
                "code": "mmol/L",
                "display": "mmol/L"
              }
            }
          ]
        },
        {
          "linkId": "chem-cl",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "2075-0"
            }
          ],
          "text": "Chloride (mmol/L)",
          "type": "decimal",
          "extension": [
            {
              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-unit",
              "valueCoding": {
                "system": "http://unitsofmeasure.org",
                "code": "mmol/L",
                "display": "mmol/L"
              }
            }
          ]
        },
        {
          "linkId": "chem-hco3",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "1963-8"
            }
          ],
          "text": "Bicarbonate (mmol/L)",
          "type": "decimal",
          "extension": [
            {
              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-unit",
              "valueCoding": {
                "system": "http://unitsofmeasure.org",
                "code": "mmol/L",
                "display": "mmol/L"
              }
            }
          ]
        },
        {
          "linkId": "chem-ca",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "17861-6"
            }
          ],
          "text": "Total calcium (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": "chem-alb",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "1751-7"
            }
          ],
          "text": "Albumin (g/dL)",
          "type": "decimal",
          "extension": [
            {
              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-unit",
              "valueCoding": {
                "system": "http://unitsofmeasure.org",
                "code": "g/dL",
                "display": "g/dL"
              }
            }
          ]
        },
        {
          "linkId": "chem-glucose",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "1558-6"
            }
          ],
          "text": "Fasting glucose (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": "chem-insulin",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "20448-7"
            }
          ],
          "text": "Fasting insulin (µU/mL)",
          "type": "decimal",
          "extension": [
            {
              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-unit",
              "valueCoding": {
                "system": "http://unitsofmeasure.org",
                "code": "u[IU]/mL",
                "display": "µU/mL"
              }
            }
          ]
        },
        {
          "linkId": "chem-anion-gap",
          "code": [
            {
              "system": "http://loinc.org",
              "code": "33037-3"
            }
          ],
          "text": "Anion gap (mmol/L)",
          "type": "decimal",
          "readOnly": true,
          "extension": [
            {
              "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-calculatedExpression",
              "valueExpression": {
                "language": "text/fhirpath",
                "expression": "((%resource.item.where(linkId='chem').item.where(linkId='chem-na').answer.valueDecimal) - ((%resource.item.where(linkId='chem').item.where(linkId='chem-cl').answer.valueDecimal) + (%resource.item.where(linkId='chem').item.where(linkId='chem-hco3').answer.valueDecimal)))"
              }
            }
          ]
        },
        {
          "linkId": "chem-corrected-ca",
          "text": "Albumin-corrected calcium (mg/dL)",
          "type": "decimal",
          "readOnly": true,
          "extension": [
            {
              "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-calculatedExpression",
              "valueExpression": {
                "language": "text/fhirpath",
                "expression": "((%resource.item.where(linkId='chem').item.where(linkId='chem-ca').answer.valueDecimal) + (0.8 * (4 - (%resource.item.where(linkId='chem').item.where(linkId='chem-alb').answer.valueDecimal)))).round(1)"
              }
            }
          ]
        },
        {
          "linkId": "chem-homa-ir",
          "text": "HOMA-IR",
          "type": "decimal",
          "readOnly": true,
          "extension": [
            {
              "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-calculatedExpression",
              "valueExpression": {
                "language": "text/fhirpath",
                "expression": "(((%resource.item.where(linkId='chem').item.where(linkId='chem-glucose').answer.valueDecimal) * (%resource.item.where(linkId='chem').item.where(linkId='chem-insulin').answer.valueDecimal)) / 405).round(2)"
              }
            }
          ]
        }
      ]
    }
  ]
}