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When a performing laboratory or imaging facility completes a diagnostic study, the results are represented in FHIR as a [`DiagnosticReport`](/content/docs/api/fhir/resources/diagnosticreport/index.html) linked to individual [`Observation`](/content/docs/api/fhir/resources/observation/index.html) resources. This guide covers how results connect back to orders, how to structure them for display, and how to handle abnormal findings.

## How Results Connect to Orders

Every `DiagnosticReport` should reference the original order via `basedOn`. This link is what allows the UI to display results in the context of the order that requested them.

basedOn

result

result

ServiceRequest (order)

DiagnosticReport (results summary)

Observation (Glucose)

Observation (BUN)

A single `ServiceRequest` (e.g. a panel order) produces one `DiagnosticReport` containing multiple `Observation` results. Each `Observation` records a single measurement with its value, units, and reference range.

## DiagnosticReport Structure

A completed lab result looks like the following:

```json
{

"resourceType": "DiagnosticReport",

"status": "final",

"category": [

{

"coding": [{

"system": "http://terminology.hl7.org/CodeSystem/v2-0074",

"code": "LAB",

"display": "Laboratory"

}]

}

],

"code": {

"coding": [{

"system": "http://loinc.org",

"code": "24323-8",

"display": "Comprehensive metabolic 2000 panel - Serum or Plasma"

}]

},

"subject": { "reference": "Patient/example" },

"basedOn": [{ "reference": "ServiceRequest/order-123" }],

"issued": "2024-07-15T14:30:00Z",

"result": [

{ "reference": "Observation/glucose-result" },

{ "reference": "Observation/bun-result" }

]

}
```

### Category Coding

The `category` field determines where a report appears in the UI. The Medplum provider app uses the `v2-0074` code system to classify reports:

| Code | Display | Use |
| --- | --- | --- |
| `LAB` | Laboratory | General lab results; required for the patient summary sidebar |
| `HM` | Hematology | Specialty subtype (always pair with `LAB`) |
| `CH` | Chemistry | Specialty subtype (always pair with `LAB`) |
| `MB` | Microbiology | Specialty subtype (always pair with `LAB`) |

caution

Reports that only include a specialty code without `LAB` will not appear in the patient summary sidebar. Always include at least one `LAB` category entry alongside any specialty categories.

### Report Status

The `DiagnosticReport.status` field tracks the lifecycle of the result:

| Status | Meaning |
| --- | --- |
| `registered` | Report has been created but results are not yet available |
| `partial` | Some results are available but the report is incomplete |
| `preliminary` | Results are available but not yet verified or finalized |
| `final` | Report is complete and verified |
| `amended` | Report was modified after being finalized |
| `corrected` | Report was corrected due to an error in a previously finalized result |
| `cancelled` | Report was cancelled (e.g. specimen was rejected) |

## Observation Results

Each line item in a lab report is an [`Observation`](/content/docs/api/fhir/resources/observation/index.html):

```json
{

"resourceType": "Observation",

"status": "final",

"category": [

{

"coding": [{

"system": "http://terminology.hl7.org/CodeSystem/observation-category",

"code": "laboratory",

"display": "Laboratory"

}]

}

],

"code": {

"coding": [{

"system": "http://loinc.org",

"code": "2345-7",

"display": "Glucose [Mass/volume] in Serum or Plasma"

}]

},

"subject": { "reference": "Patient/example" },

"valueQuantity": {

"value": 95,

"unit": "mg/dL",

"system": "http://unitsofmeasure.org",

"code": "mg/dL"

},

"referenceRange": [

{

"low": { "value": 70, "unit": "mg/dL" },

"high": { "value": 100, "unit": "mg/dL" }

}

],

"interpretation": [

{

"coding": [{

"system": "http://terminology.hl7.org/CodeSystem/v3-ObservationInterpretation",

"code": "N",

"display": "Normal"

}]

}

]

}
```

### Reference Ranges and Interpretation

Each `Observation` can carry a `referenceRange` that defines the expected normal range for the measured value. The `interpretation` field provides a coded flag (e.g. `N` for normal, `H` for high, `L` for low, `HH` / `LL` for critically abnormal).

Reference ranges may come from the performing lab as part of the result, or they can be configured by clinical administrators using [`ObservationDefinition`](/content/docs/api/fhir/resources/observationdefinition/index.html) resources.

### Critical and Abnormal Results

When a result falls outside the expected range, the `interpretation` code signals the severity:

| Code | Meaning |
| --- | --- |
| `N` | Normal |
| `H` | High |
| `L` | Low |
| `HH` | Critically high |
| `LL` | Critically low |
| `A` | Abnormal |

For integration-based workflows, the receiving system may also create a [`DetectedIssue`](/content/docs/api/fhir/resources/detectedissue/index.html) resource to flag clinical workflow concerns such as unsolicited results or unmatched patients.

## Imaging Results

Imaging results follow the same `DiagnosticReport` pattern but typically differ in structure:

- The `category` uses an imaging-specific code (e.g. `RAD` for radiology).
- Reports often include a narrative interpretation in `DiagnosticReport.conclusion` rather than discrete `Observation` values.
- The original study may be attached via `DiagnosticReport.presentedForm` (e.g. a PDF radiology report) or `DiagnosticReport.imagingStudy` for DICOM references.

```json
{

"resourceType": "DiagnosticReport",

"status": "final",

"category": [

{

"coding": [{

"system": "http://terminology.hl7.org/CodeSystem/v2-0074",

"code": "RAD",

"display": "Radiology"

}]

}

],

"code": {

"coding": [{

"system": "http://loinc.org",

"code": "36643-5",

"display": "XR Chest 2 Views"

}]

},

"subject": { "reference": "Patient/example" },

"basedOn": [{ "reference": "ServiceRequest/imaging-order-456" }],

"conclusion": "No acute cardiopulmonary abnormality."

}
```

## Integrations

Results can arrive through multiple paths depending on your integration:

- [Health Gorilla](/content/docs/integration/health-gorilla/receiving-results/index.html) synchronizes structured lab results from Quest, Labcorp, and regional labs as FHIR resources via a Medplum Bot.
- Direct HL7v2 feeds can be mapped to FHIR using the [HL7 Interface](/content/docs/integration/hl7-interfacing/index.html) and [Bots](/content/docs/bots/index.html).
- Organizations with internal labs can create `DiagnosticReport` and `Observation` resources directly via the FHIR API.

Regardless of the ingestion path, the same FHIR resource patterns apply: `DiagnosticReport` references the `ServiceRequest` via `basedOn`, and individual measurements are stored as `Observation` resources linked through `result.`