FHIR CodeSystem/$diff for vocabulary version changes - OMOPHub.com API

Overview

Compares concepts between two OMOP vocabulary releases. Returns counts and details of added and deprecated concepts. This is an OMOPHub-exclusive operation with no FHIR standard equivalent.

Request

curl "https://fhir.omophub.com/fhir/r4/CodeSystem/\$diff?\
from=2025.2&to=2026.1&count=5" \
  -H "Authorization: Bearer YOUR_API_KEY"

With vocabulary filter

curl "https://fhir.omophub.com/fhir/r4/CodeSystem/\$diff?\
from=2025.2&to=2026.1&system=http://snomed.info/sct&count=10" \
  -H "Authorization: Bearer YOUR_API_KEY"

Parameters

Parameter	Type	Required	Description
`from`	string	Yes	Old vocabulary version. Accepts OMOPHub version (`2025.2`) or FHIR ID (`omop-v20250827`)
`to`	string	Yes	New vocabulary version. Same formats as `from`
`system`	uri	No	Filter to a specific vocabulary
`count`	integer	No	Max detail entries per category (default: 100, max: 1000)

Response

{
  "resourceType": "Parameters",
  "parameter": [
    { "name": "from", "valueString": "2025.2" },
    { "name": "to", "valueString": "2026.1" },
    { "name": "total-added", "valueInteger": 1247 },
    { "name": "total-deprecated", "valueInteger": 83 },
    {
      "name": "added",
      "part": [
        { "name": "code", "valueCode": "1234567" },
        { "name": "display", "valueString": "New concept name" },
        {
          "name": "property",
          "part": [
            { "name": "code", "valueCode": "vocabulary-id" },
            { "name": "value", "valueCode": "SNOMED" }
          ]
        }
      ]
    },
    {
      "name": "deprecated",
      "part": [
        { "name": "code", "valueCode": "7654321" },
        { "name": "display", "valueString": "Deprecated concept" },
        {
          "name": "property",
          "part": [
            { "name": "code", "valueCode": "invalid-reason" },
            { "name": "value", "valueCode": "U" }
          ]
        }
      ]
    }
  ]
}

Errors

HTTP	Issue Code	Cause
400	`invalid`	Missing `from` or `to` parameter, or unknown system URI
404	`not-found`	Version not found in vocabulary releases