What does the lastUpdated timestamp represent in a FHIR resource?

• A. The time the resource was created
• B. The time the server last accessed the resource
• C. The timestamp of the last update to the resource's version
• D. The time the resource's profile was last updated

Answer: (C)

In a FHIR resource, the lastUpdated timestamp is part of the resource’s metadata and records when the current version of the resource was created. This means it reflects the most recent change to that resource: every time a new version is created—whether on creation or after an update—the lastUpdated value is set to that moment. For example, you might create a resource at 2024-01-01, giving it version 1 and lastUpdated 2024-01-01; then update the resource later, which creates version 2 and updates lastUpdated to the time of that update. It does not indicate server access times, nor is it specifically about the resource’s profile unless such a change accompanies a new version.