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curl -X GET "https://api.omophub.com/v1/concept-classes?include_stats=true" \
  -H "Authorization: Bearer YOUR_API_KEY"

{
  "success": true,
  "data": {
    "concept_classes": [
      {
        "concept_class_id": "Clinical Finding",
        "concept_class_name": "Clinical Finding",
        "concept_class_concept_id": 441840,
        "concept_count": 425891,
        "vocabulary_coverage": ["SNOMED", "Read"]
      },
      {
        "concept_class_id": "Ingredient",
        "concept_class_name": "Ingredient",
        "concept_class_concept_id": 441828,
        "concept_count": 45678,
        "vocabulary_coverage": ["RxNorm", "SNOMED"]
      },
      {
        "concept_class_id": "Procedure",
        "concept_class_name": "Procedure",
        "concept_class_concept_id": 441838,
        "concept_count": 198765,
        "vocabulary_coverage": ["SNOMED", "HCPCS"]
      }
    ]
  },
  "meta": {
    "request_id": "req_abc123",
    "vocab_release": "2025.1",
    "timestamp": "2025-01-05T10:00:00Z"
  }
}
This endpoint returns concept classes, which provide categorization of medical concepts within their domains. Concept classes distinguish between different types of concepts like “Clinical Finding” vs “Disorder” within conditions, or “Ingredient” vs “Clinical Drug” within drugs.

​
Query Parameters

​
vocabulary_ids
string
Filter concept classes to those used by specific vocabularies. Comma-separated list.
Example: SNOMED,RxNorm,ICD10CM
​
include_stats
boolean
default:"false"
Include concept counts and vocabulary coverage for each concept class.
​
vocab_release
string
Specific vocabulary release version to query
Example: 2025.1

​
Response

​
success
boolean
Indicates if the request was successful.
​
data
object
Response data container.
​
meta
object
Response metadata.
curl -X GET "https://api.omophub.com/v1/concept-classes?include_stats=true" \
  -H "Authorization: Bearer YOUR_API_KEY"

{
  "success": true,
  "data": {
    "concept_classes": [
      {
        "concept_class_id": "Clinical Finding",
        "concept_class_name": "Clinical Finding",
        "concept_class_concept_id": 441840,
        "concept_count": 425891,
        "vocabulary_coverage": ["SNOMED", "Read"]
      },
      {
        "concept_class_id": "Ingredient",
        "concept_class_name": "Ingredient",
        "concept_class_concept_id": 441828,
        "concept_count": 45678,
        "vocabulary_coverage": ["RxNorm", "SNOMED"]
      },
      {
        "concept_class_id": "Procedure",
        "concept_class_name": "Procedure",
        "concept_class_concept_id": 441838,
        "concept_count": 198765,
        "vocabulary_coverage": ["SNOMED", "HCPCS"]
      }
    ]
  },
  "meta": {
    "request_id": "req_abc123",
    "vocab_release": "2025.1",
    "timestamp": "2025-01-05T10:00:00Z"
  }
}

​
Usage Examples

​
All Concept Classes

Get all concept classes without statistics: 
GET /v1/concept-classes

​
With Statistics

Get concept classes with concept counts and vocabulary coverage: 
GET /v1/concept-classes?include_stats=true

​
Filter by Vocabulary

Get concept classes used by specific vocabularies: 
GET /v1/concept-classes?vocabulary_ids=SNOMED,RxNorm&include_stats=true

​
Notes

  • Concept classes provide finer categorization than domains
  • Many concept classes are vocabulary-specific (e.g., “3-char billing code” for ICD codes)
  • When filtering by vocabulary, only concept classes that contain concepts from those vocabularies are returned
  • The vocabulary_coverage field shows which vocabularies contribute concepts to each class