201709 LastN Query Track

Last N Observations Query Track

Submitting WG/Project/Implementer Group

Orders and Observations WorkGroup

Justification

The lastn query meets the common need for searching for the most recent or last n=number of observations for a subject.

Examples where this query could be used:

• Fetch the last 5 temperatures for a patient to view trends
• Get the most recent lab results for patient
• Fetch the last 3 results for all vitals for a patient

The $lastn operation is has been introduced as part of FHIR STU3, but has not yet undergone yet been widley implemented. This goal of this track is encourage server implementation of the operation, uncover implementation issues, and help evaluate if similar operations would be useful for other clinical resources such DiagnosticReport.

Proposed Track Lead

Eric Haas

Expected participants

Servers:

• Grahame's test server
• Cerner

Roles & Scenarios

For context, roles, and scenarios of the FHIR Query and FHIR Server and Scenarios, refere to the lastn Operation Definition and the examples in the FHIR Specification here

Roles:

• Query Requester: User who makes an API request
• Query Responder: FHIR Server

Action:

1. Following the Example in the Specification, requester make an api request to the FHIR server
2. FHIR server returns the the requested resource Bundle or appropriate error/OperationDefinition

Precondition:

• This server has a baseURL (see the FHIR specification)

Success Criteria:

• FHIR Server returns expected resources in bundle as outlined in the speicifiation example

Bonus point:

• Make additional lastn requests to determine limitations of operation.
• Extend lastn operation to DiagnosticReport resource (e.g., fetch me the last 3 CBC's for Mrs Smith)