> ## Documentation Index
> Fetch the complete documentation index at: https://docs.omophub.com/llms.txt
> Use this file to discover all available pages before exploring further.

# ConceptMap read

> Read a single HL7 FHIR-to-OMOP IG ConceptMap by id.

## Overview

`GET /fhir/{version}/ConceptMap/{id}` returns a single [HL7 FHIR-to-OMOP IG](https://hl7.org/fhir/uv/omop/INFORMATIVE1/en/) ConceptMap as a FHIR `ConceptMap` resource. The `{id}` is the IG artifact id, e.g. `GenderClass`, `EncounterClass`, `ConditionStatusConcepts`, `ImmunizationVaccine`.

## Request

```bash theme={null}
curl "https://fhir.omophub.com/fhir/r4/ConceptMap/EncounterClass" \
  -H "Authorization: Bearer oh_your_api_key"
```

## Response

```json theme={null}
{
  "resourceType": "ConceptMap",
  "id": "EncounterClass",
  "url": "http://hl7.org/fhir/uv/omop/ConceptMap/EncounterClass",
  "version": "1.0.0",
  "status": "active",
  "group": [
    {
      "source": "http://terminology.hl7.org/CodeSystem/v3-ActCode",
      "target": "https://fhir-terminology.ohdsi.org",
      "element": [
        {
          "code": "IMP",
          "target": [
            {
              "code": "9201",
              "display": "Inpatient Visit",
              "equivalence": "equivalent"
            }
          ]
        },
        {
          "code": "OBSENC",
          "target": [
            {
              "code": "262",
              "display": "Emergency Room and Inpatient Visit",
              "equivalence": "narrower",
              "comment": "The source code does not necessarily mean that the patient has moved to an inpatient visit"
            }
          ]
        }
      ]
    }
  ]
}
```

<Note>
  On `/fhir/r5/` and `/fhir/r6/`, target entries use the FHIR R5 `relationship`
  code (e.g. `source-is-broader-than-target`) instead of R4 `equivalence`.
  Source codes the IG leaves unmapped appear as target-less elements.
</Note>

An unknown id returns a `404` `OperationOutcome`.

## See also

* [ConceptMap search](/api-reference/fhir-terminology/conceptmap-search) - list all hosted maps