> ## 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 search

> List or look up the HL7 FHIR-to-OMOP IG ConceptMaps hosted by OMOPHub.

## Overview

`GET /fhir/{version}/ConceptMap` returns the [HL7 FHIR-to-OMOP Implementation Guide](https://hl7.org/fhir/uv/omop/INFORMATIVE1/en/) ConceptMaps that OMOPHub hosts — gender, encounter class/admit-source/discharge-disposition, condition status, allergy/intolerance categories, immunization route/source, vital signs, blood pressure, vaccine, and clinical-findings maps. These back the `$translate` `url` parameter (see [\$translate](/api-reference/fhir-terminology/translate)) and let IG-driven tooling discover the maps by canonical URL.

<Note>
  Targets use FHIR R4 `equivalence` on `/fhir/r4/` and `/fhir/r4b/`, and the R5
  `relationship` code on `/fhir/r5/` and `/fhir/r6/`.
</Note>

## Request

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

```bash Filter by canonical URL theme={null}
curl "https://fhir.omophub.com/fhir/r4/ConceptMap?url=http://hl7.org/fhir/uv/omop/ConceptMap/GenderClass" \
  -H "Authorization: Bearer oh_your_api_key"
```

## Response

A FHIR searchset `Bundle`. With no `url`, every hosted ConceptMap is returned; with a `url`, a single-entry Bundle (or an empty Bundle, `total: 0`, for an unknown URL, per FHIR search semantics).

```json theme={null}
{
  "resourceType": "Bundle",
  "type": "searchset",
  "total": 1,
  "entry": [
    {
      "fullUrl": "https://fhir.omophub.com/fhir/r4/ConceptMap/GenderClass",
      "resource": {
        "resourceType": "ConceptMap",
        "id": "GenderClass",
        "url": "http://hl7.org/fhir/uv/omop/ConceptMap/GenderClass",
        "version": "1.0.0",
        "status": "active",
        "group": [
          {
            "source": "http://hl7.org/fhir/administrative-gender",
            "target": "https://fhir-terminology.ohdsi.org",
            "element": [
              {
                "code": "male",
                "target": [
                  {
                    "code": "8507",
                    "display": "Male",
                    "equivalence": "equivalent"
                  }
                ]
              }
            ]
          }
        ]
      }
    }
  ]
}
```

## See also

* [ConceptMap read](/api-reference/fhir-terminology/conceptmap-read) - fetch one map by id
* [\$translate](/api-reference/fhir-terminology/translate) - translate codes, optionally via a specific ConceptMap `url`