Specification

This page covers the elements of the FHIR R4 Observation resource that Rad AI Reporting actually reads: what it takes to find an Observation for a study, and what it takes to get a value out of one. See Template Integration for how a matched Observation's value gets into a report.

Element descriptions and cardinality

Element                       Card.  Comment
---------------------------------------------------------------------------------------------------
Observation
├── resourceType              1..1   The type of the resource
├── status                    1..1   ObservationStatus binding
├── subject                   1..1   A reference to the patient
│   └── identifier            1..1   Logical reference to the patient
│       ├── system            0..1   The assigning system for the patient identifier
│       └── value             1..1   The patient's MRN
├── partOf                    1..1   A reference to the study
│   └── identifier            1..1   Logical reference to the study
│       ├── system            0..1   The assigning system for the accession number
│       ├── value             1..1   The accession number
│       └── type              1..1   The kind of identifier
│           └── coding        1..1   Identifier type must match:
│               ├── system    1..1   "http://terminology.hl7.org/CodeSystem/v2-0203"
│               └── code      1..1   "ACSN"
├── code                      1..1   The code being observed
│   └── coding                1..1   Only the first coded element is used
│       ├── system            0..1   The coding system
│       ├── code              1..1   Matched against observationValue(code)
│       └── display           0..1   Optional label, human-friendly value
├── valueQuantity             0..1   See Template Integration
│   ├── value                 1..1   The numeric value of the observation
│   └── unit                  0..1   Optionally displayed alongside the value
├── valueString               0..1   See Template Integration
└── text                      0..1   Narrative fallback, used only if no value[x] is present
    ├── status                1..1   Required if text is present
    └── div                   1..1   The narrative, in XHTML

FHIR's value[x] pattern means only one of valueQuantity or valueString can be set on a given Observation.

Example Resource

{
  "resourceType": "Observation",
  "status": "final",
  "subject": {
    "identifier": {
      "system": "http://example.org/patient-ids",
      "value": "1234"
    }
  },
  "partOf": [
    {
      "identifier": {
        "system": "http://example.org/filler-order-number",
        "value": "1234",
        "type": {
          "coding": [
            {
              "system": "http://terminology.hl7.org/CodeSystem/v2-0203",
              "code": "ACSN"
            }
          ]
        }
      }
    }
  ],
  "code": {
    "coding": [
      {
        "system": "http://loinc.org",
        "code": "10231-9",
        "display": "Right ventricular Ejection fraction"
      }
    ]
  },
  "valueQuantity": {
    "value": 29,
    "unit": "%"
  }
}