The BETA versions of the Transfer of Care message specifications are now published; these are sufficiently mature to enable suppliers to development against. There are no plans to change the specifications other than to react to defects reported by implementers. The specifications can be found here
The Transfer of Care FHIR messages will use the ITK3 (Interoperability Toolkit) specification available here.
NHS Digital has developed an ITK3 Test Harness which is currently under test by implementers. FHIR messages can be sent using MESH from sender to recipient as per the ITK3 specifications. To ensure that senders are clear on the successful receipt or otherwise of their messages, the ITK3 Test Harness produces standard acknowledgements, including those reporting failures of messages.
Currently, the ITK3 Test Harness simulates the response of a receiving primary care system, but it is intended to replicate this for a hospital sending system as well.
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