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curl -G "https://api.omophub.com/v1/concepts/201826/relationships" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  --data-urlencode "relationship_ids=Is a,Maps to" \
  --data-urlencode "page_size=50"

{
  "success": true,
  "data": {
    "relationships": [
      {
        "concept_id_1": 201826,
        "concept_id_2": 73211009,
        "relationship_id": "Is a",
        "relationship_name": "Is a",
        "reverse_relationship_id": "Subsumes",
        "concept_1": {
          "concept_id": 201826,
          "concept_name": "Type 2 diabetes mellitus",
          "concept_code": "44054006",
          "vocabulary_id": "SNOMED",
          "vocabulary_name": "SNOMED",
          "domain_id": "Condition",
          "concept_class_id": "Clinical Finding",
          "standard_concept": "S",
          "valid_start_date": "2002-01-31",
          "valid_end_date": "2099-12-31",
          "invalid_reason": null
        },
        "concept_2": {
          "concept_id": 73211009,
          "concept_name": "Diabetes mellitus",
          "concept_code": "73211009",
          "vocabulary_id": "SNOMED",
          "vocabulary_name": "SNOMED",
          "domain_id": "Condition",
          "concept_class_id": "Clinical Finding",
          "standard_concept": "S",
          "valid_start_date": "2002-01-31",
          "valid_end_date": "2099-12-31",
          "invalid_reason": null
        },
        "valid_start_date": "2002-01-31",
        "valid_end_date": "2099-12-31",
        "invalid_reason": null
      }
    ]
  },
  "meta": {
    "request_id": "req_abc123",
    "timestamp": "2025-01-04T10:30:00Z",
    "vocab_release": "2025.1",
    "version": "2025.1",
    "duration": 45,
    "pagination": {
      "page": 1,
      "page_size": 100,
      "total_items": 47,
      "total_pages": 1,
      "has_next": false,
      "has_previous": false
    }
  }
}
This endpoint provides relationship information for a concept, showing how it connects to other concepts through various relationship types such as “Is a”, “Part of”, “Has ingredient”, and others in medical vocabularies.

​
Path Parameters

​
concept_id
integer
required
The unique identifier of the concept to retrieve relationships for
Example: 201826 (Type 2 diabetes mellitus)

​
Query Parameters

​
relationship_ids
string
Comma-separated list of relationship IDs to filter by
Example: Is a,Maps to,Has finding site
​
vocabulary_ids
string
Filter relationships to specific vocabularies
Example: SNOMED,ICD10CM,RxNorm
​
domain_ids
string
Filter related concepts to specific domains
Example: Condition,Drug,Procedure
​
standard_only
boolean
default:"false"
Only return relationships to standard concepts
​
include_invalid
boolean
default:"true"
Include relationships to deprecated/invalid concepts
​
include_reverse
boolean
default:"false"
Include reverse relationships (where this concept is concept_id_2)
​
page
integer
default:"1"
Page number for pagination (1-based)
​
page_size
integer
default:"100"
Number of relationships to return per page (max 1000)
​
vocab_release
string
Specific vocabulary release version
Example: 2025.1

​
Response

​
relationships
array
Array of relationship objects
​
meta
object
Response metadata including pagination
curl -G "https://api.omophub.com/v1/concepts/201826/relationships" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  --data-urlencode "relationship_ids=Is a,Maps to" \
  --data-urlencode "page_size=50"

{
  "success": true,
  "data": {
    "relationships": [
      {
        "concept_id_1": 201826,
        "concept_id_2": 73211009,
        "relationship_id": "Is a",
        "relationship_name": "Is a",
        "reverse_relationship_id": "Subsumes",
        "concept_1": {
          "concept_id": 201826,
          "concept_name": "Type 2 diabetes mellitus",
          "concept_code": "44054006",
          "vocabulary_id": "SNOMED",
          "vocabulary_name": "SNOMED",
          "domain_id": "Condition",
          "concept_class_id": "Clinical Finding",
          "standard_concept": "S",
          "valid_start_date": "2002-01-31",
          "valid_end_date": "2099-12-31",
          "invalid_reason": null
        },
        "concept_2": {
          "concept_id": 73211009,
          "concept_name": "Diabetes mellitus",
          "concept_code": "73211009",
          "vocabulary_id": "SNOMED",
          "vocabulary_name": "SNOMED",
          "domain_id": "Condition",
          "concept_class_id": "Clinical Finding",
          "standard_concept": "S",
          "valid_start_date": "2002-01-31",
          "valid_end_date": "2099-12-31",
          "invalid_reason": null
        },
        "valid_start_date": "2002-01-31",
        "valid_end_date": "2099-12-31",
        "invalid_reason": null
      }
    ]
  },
  "meta": {
    "request_id": "req_abc123",
    "timestamp": "2025-01-04T10:30:00Z",
    "vocab_release": "2025.1",
    "version": "2025.1",
    "duration": 45,
    "pagination": {
      "page": 1,
      "page_size": 100,
      "total_items": 47,
      "total_pages": 1,
      "has_next": false,
      "has_previous": false
    }
  }
}

​
Usage Examples

​
All Relationships

Get all relationships for a concept: 
curl "https://api.omophub.com/v1/concepts/201826/relationships" \
  -H "Authorization: Bearer YOUR_API_KEY"

​
Hierarchical Relationships Only

Retrieve only “Is a” relationships: 
curl "https://api.omophub.com/v1/concepts/201826/relationships?relationship_ids=Is%20a" \
  -H "Authorization: Bearer YOUR_API_KEY"

​
Cross-Vocabulary Mappings

Find mappings to ICD-10: 
curl "https://api.omophub.com/v1/concepts/201826/relationships?relationship_ids=Maps%20to&vocabulary_ids=ICD10CM" \
  -H "Authorization: Bearer YOUR_API_KEY"

​
Including Reverse Relationships

Include relationships where this concept is the target: 
curl "https://api.omophub.com/v1/concepts/201826/relationships?include_reverse=true" \
  -H "Authorization: Bearer YOUR_API_KEY"

​
Notes

  • Relationships are bidirectional in the database; use include_reverse=true to see both directions
  • Standard concepts are not filtered by default; use standard_only=true to filter
  • Large concepts may have hundreds of relationships - use pagination appropriately
  • The response includes full concept details for both source and target concepts