These patterns are often implemented with middleware support, these can be a number of components such as a Trust Integration Engine (TIE), Message Queue (MQ)/MESH, etc. The communication is generally point to point between the placer and the filler.
FHIR documentation on these patterns can be found on Ad-Hoc Workflow Communication Patterns. In particular Messaging request from placer to filler & acknowledgment
Pathology is commonly implemented in the NHS using HL7 v2 Messages. The national standards follow a similar pattern using EDIFACT, HL7 v3 and FHIR STU3 Pathology Messages. The HL7 FHIR version is used for illustration of the pattern.
- The Test Request is created in the EPR or Order Comms software, it is sent to the laboratory via the TIE. (HL7 v2.4 OML_O21 - Laboratory order)
- The TIE forwards on the request to the Laboratory
- The laboratory performs the test and send out the results via the TIE. (HL7 v2.4 ORU_R01 - Unsolicited transmission of an observation message)
- The TIE forwards the results (response) to the requester, this response may also go via MESH is the requester is in primary care sector. The TIE may choose to distribute the results to other recipients.
Booking and Referral Standard
BARS is designed around traditional point to point messaging exchanges which are implemented as FHIR Messages. This is similar to Pathology workflow above with the addition of a central registry to record ServiceRequests. It is also similar to HL7 v2.4 REF_I12 Patient Referral and associated response messages (REF_I13 Modify Patient Referral and REF_I14 Cancel Patient Referral
- The referral is sent to the BARS POST /$process-message endpoint (https://digital.nhs.uk/developer/api-catalogue/booking-and-referral-fhir#api-Message-processMessage)
- This referral is then routed to the services POST /$process-message endpoint
- The service can respond via the BARS POST /$process-message endpoint (https://digital.nhs.uk/developer/api-catalogue/booking-and-referral-fhir#api-Message-processMessage)
- This response is then routed to the referrers POST /$process-message endpoint
- As the ServiceRequest is being actioned/fulfilled, the service will generate event notifications. These are generally out of scope for eRS workflow and will include a wide variety of event notifications such as ADT messages, discharge letters, etc.
- The referrer and service can check on the status of the referral as required via querying BARS FHIR RESTful ServiceRequest endpoint (https://digital.nhs.uk/developer/api-catalogue/booking-and-referral-fhir#api-Referral)