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This guide covers how to order laboratory tests and imaging studies using Medplum, from building order forms through tracking results. For the FHIR data model overview, see [Labs & Imaging](/content/docs/labs-imaging/index.html). For medication ordering, see the [Medications](/content/docs/medications/index.html) section.

## End-to-End Ordering Flow

A typical diagnostic ordering workflow moves through five stages, each represented by FHIR resources and status transitions.

1. A clinician identifies the need for a diagnostic test or imaging study during a patient encounter.
2. The order is captured through a Computerized Physician Order Entry (CPOE) form, creating a [`ServiceRequest`](/content/docs/api/fhir/resources/servicerequest/index.html) resource.
3. The order is transmitted to the performing laboratory or imaging facility, either via an integration (e.g. [Health Gorilla](/content/docs/integration/health-gorilla/index.html)) or an internal process.
4. The `ServiceRequest.status` is updated as the order progresses through its lifecycle.
5. Results arrive as [`DiagnosticReport`](/content/docs/api/fhir/resources/diagnosticreport/index.html) and [`Observation`](/content/docs/api/fhir/resources/observation/index.html) resources linked back to the original order. See [Results and Review](/content/docs/labs-imaging/results-and-review/index.html) for details.

## Order Form (CPOE)

Certified EHRs are required to support CPOE for Medications, Labs, and Imaging. These correspond to the ONC (a)(1), (a)(2), and (a)(3) criteria described on [HealthIT.gov](https://www.healthit.gov/test-method/computerized-provider-order-entry-cpoe-medications).

Building a custom CPOE form that represents an organization's [Diagnostic Catalog](/content/docs/careplans/diagnostic-catalog/index.html) and enabling the appropriate provider integrations are the first steps. The form needs to capture:

- Which tests to order (e.g. HbA1c) and which performing lab (e.g. ACME Clinical Lab)
- Ask on Entry (AOE) questions specific to the test (e.g. whether the patient is fasted for a Renal Panel)
- Specimen details including collection time and specimen type
- Billing and insurance information indicating which account or payor should cover the test

This [questionnaire](https://storybook.medplum.com/?path=/story/medplum-questionnaireform--lab-ordering) demonstrates a sample CPOE order form and can be added to your Medplum app or provider-facing application.

## ServiceRequest Lifecycle

The [`ServiceRequest`](/content/docs/api/fhir/resources/servicerequest/index.html) resource tracks the full lifecycle of a diagnostic order. FHIR R4 defines the following status values:

| Status | Meaning |
| --- | --- |
| `draft` | Order is being composed but not yet finalized |
| `active` | Order has been placed and is awaiting fulfillment |
| `on-hold` | Order is temporarily paused or suspended |
| `completed` | Results have been received and the order is fulfilled |
| `revoked` | Order was cancelled before completion |
| `entered-in-error` | Order was created by mistake and should be disregarded |

### Creating an Order

When a clinician finalizes an order, create a `ServiceRequest` linked to the patient and, when applicable, the encounter:

```json
{
  "resourceType": "ServiceRequest",
  "status": "active",
  "intent": "order",
  "category": [{
    "coding": [{
      "system": "http://snomed.info/sct",
      "code": "108252007",
      "display": "Laboratory procedure"
    }]
  }],
  "code": {
    "coding": [{
      "system": "http://loinc.org",
      "code": "24323-8",
      "display": "Comprehensive metabolic 2000 panel - Serum or Plasma"
    }]
  },
  "subject": { "reference": "Patient/example" },
  "encounter": { "reference": "Encounter/visit-123" },
  "requester": { "reference": "Practitioner/dr-smith" },
  "performer": [{ "reference": "Organization/acme-lab" }],
  "priority": "routine"
}
```

The `intent` field is always `order` for clinician-placed orders. Use `priority` to distinguish routine orders from urgent/stat requests (`routine`, `urgent`, `asap`, `stat`).

### Cancelling and Amending Orders

To cancel an order that has not yet been fulfilled, update the `ServiceRequest.status` to `revoked`. If the order was created by mistake, use `entered-in-error` instead.

To amend an order (e.g. adding tests or changing the performing lab), update the existing `ServiceRequest` rather than creating a duplicate. If the integration partner requires a new transmission, coordinate cancellation of the original and creation of a replacement, linking them via `ServiceRequest.replaces`.

### Linking Orders to Encounters

When an order is placed during a visit, set `ServiceRequest.encounter` to reference the active [`Encounter`](/content/docs/api/fhir/resources/encounter/index.html). This allows the encounter chart to display all orders associated with the visit via a search like `ServiceRequest?encounter=Encounter/{id}`.

## Laboratory vs. Imaging Orders

While both laboratory and imaging orders use `ServiceRequest`, there are differences in the ordering workflow:

| Aspect | Laboratory | Imaging |
| --- | --- | --- |
| Specimen | Physical sample is collected (blood, urine, etc.) with collection time and handling requirements | No specimen; patient is scheduled for a study |
| AOE questions | Common (e.g. fasting status, last menstrual period) | Less common; clinical indication and contrast preferences are typical |
| Scheduling | Specimen collection may happen at point of care or at a draw station | Study is typically scheduled as a separate appointment at a facility |
| Results | Structured `Observation` values with reference ranges | `DiagnosticReport` often includes an attached imaging report (PDF or narrative) with fewer structured observations |
| Category coding | `laboratory` (SNOMED `108252007`) | `imaging` (SNOMED `363679005`) |

For imaging orders, use `ServiceRequest.locationReference` or `ServiceRequest.locationCode` to indicate the facility where the study should be performed.

## Logistics

CPOE should account for the logistics workflow a provider organization wants to enable:

| Scenario | Implications |
| --- | --- |
| Specimen collected on site | CPOE must collect specimen time and details; support printing requisitions to attach to specimens |
| Specimen collected elsewhere | No specimen collection details on the form; patients informed of draw station location |
| At-home lab | Patient data must include an accurate mailing address |

## Integrations

Medplum is provider-agnostic and supports connecting to lab and imaging orders of all types when an integration is in place. Common integrations can be found in the [Integrations](/content/docs/integration/index.html) section.

For lab ordering specifically, the [Health Gorilla](/content/docs/integration/health-gorilla/index.html) integration provides end-to-end support including [sending orders](/content/docs/integration/health-gorilla/sending-orders/index.html), [receiving results](/content/docs/integration/health-gorilla/receiving-results/index.html), and [manual result backfill](/content/docs/integration/health-gorilla/sync-resources-from-health-gorilla/index.html), with React components and bot-based automation. Quest, Labcorp, and regional labs are commonly connected through Health Gorilla.

Organizations that connect directly to a performing lab (e.g. via HL7v2 or a proprietary API) follow the same FHIR resource patterns described here. The [HL7 Interface](/content/docs/integration/hl7-interfacing/index.html) and [On-Prem Agent](/content/docs/agent/index.html) docs cover connectivity options.

caution

Lab and imaging ordering requires setup. Contact us at [info@medplum.com](mailto:info+diagnostics@medplum.com?subject=enabling%20diagnostic%20providers) to enable a provider.

## ONC Certification

CPOE for labs and imaging corresponds to ONC criteria (a)(2) and (a)(3). Certification is in progress; follow the [GitHub issue](https://github.com/medplum/medplum/issues/3003) for updates.