{
  "resourceType": "StructureDefinition",
  "id": "DataStandardsWales-Observation-VitalSigns-BMI",
  "url": "https://fhir.nhs.wales/StructureDefinition/DataStandardsWales-Observation-VitalSigns-BMI",
  "version": "1.2.0",
  "name": "DataStandardsWalesObservationVitalSignsBMI",
  "title": "Data Standards Wales Observation Vital Signs BMI",
  "status": "active",
  "date": "2026-02-26",
  "publisher": "NHS Wales",
  "contact": [
    {
      "name": "NHS Wales",
      "telecom": [
        {
          "system": "email",
          "value": "fhir.standards@wales.nhs.uk",
          "use": "work",
          "rank": 1
        }
      ]
    }
  ],
  "description": "Resource structure is derived from Data Standards Wales - Observation - Vital Signs. It has drawn on UK Core - Observation - BMI v 1.0.0 (not yet included in a balloted release) for guidance on specific content and constraints for use when the observation is a BMI measurement.",
  "purpose": "To provide implementers with additional support when implementing measuring and recording body mass index and to provide a consistent structure to how the data is presented.",
  "copyright": "2026 NHS Wales",
  "fhirVersion": "4.0.1",
  "kind": "resource",
  "abstract": false,
  "type": "Observation",
  "baseDefinition": "https://fhir.nhs.wales/StructureDefinition/DataStandardsWales-Observation-VitalSigns",
  "derivation": "constraint",
  "differential": {
    "element": [
      {
        "id": "Observation.code.coding:loinc",
        "path": "Observation.code.coding",
        "sliceName": "loinc"
      },
      {
        "id": "Observation.code.coding:loinc.code",
        "path": "Observation.code.coding.code",
        "fixedCode": "39156-5"
      },
      {
        "id": "Observation.code.coding:snomedCT",
        "path": "Observation.code.coding",
        "sliceName": "snomedCT",
        "min": 1,
        "max": "1",
        "binding": {
          "strength": "preferred",
          "valueSet": "https://fhir.nhs.wales/ValueSet/DataStandardsWales-BMI"
        }
      },
      {
        "id": "Observation.code.coding:snomedCT.system",
        "path": "Observation.code.coding.system",
        "min": 1
      },
      {
        "id": "Observation.code.coding:snomedCT.code",
        "path": "Observation.code.coding.code",
        "min": 1
      },
      {
        "id": "Observation.value[x]",
        "path": "Observation.value[x]",
        "min": 1,
        "type": [
          {
            "code": "Quantity"
          }
        ]
      },
      {
        "id": "Observation.value[x].value",
        "path": "Observation.value[x].value",
        "min": 1
      },
      {
        "id": "Observation.value[x].system",
        "path": "Observation.value[x].system",
        "min": 1,
        "fixedUri": "http://unitsofmeasure.org"
      },
      {
        "id": "Observation.value[x].code",
        "path": "Observation.value[x].code",
        "min": 1,
        "fixedCode": "kg/m2"
      },
      {
        "id": "Observation.note.author[x]",
        "path": "Observation.note.author[x]",
        "type": [
          {
            "code": "Reference",
            "targetProfile": [
              "https://fhir.nhs.wales/StructureDefinition/DataStandardsWales-Organization",
              "https://fhir.nhs.wales/StructureDefinition/DataStandardsWales-RelatedPerson",
              "https://fhir.nhs.wales/StructureDefinition/DataStandardsWales-Patient",
              "https://fhir.nhs.wales/StructureDefinition/DataStandardsWales-Practitioner"
            ]
          },
          {
            "code": "string"
          }
        ]
      }
    ]
  }
}