ZapEHR Services
FHIR
Resource History

Resource History

Each time a FHIR resource is created or updated with the ZapEHR FHIR API, a new version of that resource is created. The versioned resource is a snapshot of what the FHIR resource looked like at the time it was created or updated. This allows for the history of a resource to be tracked, and for the value of a resource at a given point in time to be checked. It also allows for point-in-time restoration of resources if you need to roll back.

The FHIR standard defines a set of endpoints for retrieving the history of FHIR resources.

Example

For example, we created a Patient with the name Jon Snow, and then updated that patient to include an address called Winterfell. Then we called the resource _history endpoint and received this response:

{
  "resourceType": "Bundle",
  "type": "history",
  "entry": [
    {
      "fullUrl": "https://testing.fhir-api.zapehr.com/r4/Patient/6e2ef194-3bbd-4702-b51e-abe35f6c4096",
      "request": {
        "method": "PUT",
        "url": "Patient/6e2ef194-3bbd-4702-b51e-abe35f6c4096"
      },
      "response": {
        "status": "200",
        "outcome": {
          "resourceType": "OperationOutcome",
          "id": "ok",
          "issue": [
            {
              "severity": "information",
              "code": "informational",
              "details": {
                "text": "All OK"
              }
            }
          ]
        },
        "lastModified": "2023-03-24T00:19:07.550Z"
      },
      "resource": {
        "resourceType": "Patient",
        "name": [
          {
            "given": ["Jon"],
            "family": "Snow"
          }
        ],
        "id": "6e2ef194-3bbd-4702-b51e-abe35f6c4096",
        "meta": {
          "versionId": "a2be8abc-2ed2-4fde-8ed7-f83cc8603287",
          "lastUpdated": "2023-03-24T00:19:07.550Z"
        },
        "address": [
          {
            "line": ["Winterfell"]
          }
        ]
      }
    },
    {
      "fullUrl": "https://testing.fhir-api.zapehr.com/r4/Patient/6e2ef194-3bbd-4702-b51e-abe35f6c4096",
      "request": {
        "method": "POST",
        "url": "Patient"
      },
      "response": {
        "status": "200",
        "outcome": {
          "resourceType": "OperationOutcome",
          "id": "ok",
          "issue": [
            {
              "severity": "information",
              "code": "informational",
              "details": {
                "text": "All OK"
              }
            }
          ]
        },
        "lastModified": "2023-03-24T00:18:37.552Z"
      },
      "resource": {
        "resourceType": "Patient",
        "name": [
          {
            "given": ["Jon"],
            "family": "Snow"
          }
        ],
        "id": "6e2ef194-3bbd-4702-b51e-abe35f6c4096",
        "meta": {
          "versionId": "bccc4f09-d099-4782-9181-b26e7e6899b4",
          "lastUpdated": "2023-03-24T00:18:37.552Z"
        }
      }
    }
  ]
}

FHIR Blame

With this endpoint, you can get the history of resources, and determine the value of resources at different points. This helps to build functionality similar to git blame to determine when each attribute of a resource was updated, and who updated it when combined with Provenance. In the context of an EHR, this can give information such as which provider most recently updated a field, and when they updated it.

Here is this information on the ZapEHR Developer Console (opens in a new tab).

ZapEHR console history blame, with lines identifying when each attribute of a patient was most recently changed

There are also endpoints for getting specific versions of a resource, given a version id. For example, we can call _history/6e2ef194-3bbd-4702-b51e-abe35f6c4096 and receive this response:

{
  "resourceType": "Patient",
  "name": [
    {
      "given": ["Jon"],
      "family": "Snow"
    }
  ],
  "id": "6e2ef194-3bbd-4702-b51e-abe35f6c4096",
  "meta": {
    "versionId": "bccc4f09-d099-4782-9181-b26e7e6899b4",
    "lastUpdated": "2023-03-24T00:18:37.552Z"
  }
}

History in building applications

The history of resources can be helpful when building applications. It can provide a timeline of a Patient's medical records, and give information about who updated attributes.

Further reading

For more information, refer to the FHIR API documentation (opens in a new tab), and particularly vread (opens in a new tab) and history (opens in a new tab).

ExtensibilityResource Provenance