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Explore and Make use of Nationally Defined Messaging APIs


Develop Overview

Overarching development principles when using FHIR


This implementation guidance defines a Minimum Viable Product (MVP) for each FHIR Resource required to support the target use case of medication requests from a hospital ePMA system to a hospital pharmacy system.

An implementation is recommended to adhere to the MVP but can also choose to implement other elements from the chosen FHIR standard. For the purposes of this guidance, an “implementation” is the partnership between an ePMA system supplier and a hospital pharmacy system supplier within a given Trust.

The MVP requires the implementation of four FHIR Resources; MedicationRequest, Medication, Patient and Practitioner

FHIR Resource Relationships (MVP)

The MedicationRequest can reference many other FHIR resources but the four above are required for the recommended MVP.

MVP Terms Used Within This Guidance

The elements available within each FHIR resource are described as follows;

  • Mandatory, must be populated as mandatory as per the FHIR standard
  • Required, optional within the FHIR standard but form part of the recommended MVP
  • Optional, optional within the FHIR standard which do not form part of the recommended MVP

Which Version Of The FHIR Standard To Implement?

This guidance aligns with three versions of the FHIR standard; STU3, CareConnect (a UK extension of STU3) and R4.

Work is on-going to define a UK-specific version of the R4 standard known as R4 UK Core. Until the implementation of the MedicationRequest resource has been published within UK Core, the use of the R4 standard in this guidance is for information only. It can inform a migration plan from STU3 or CareConnect once the R4 Core UK resources are published as active.

The MVP recommended within this guidance can be implemented with either STU3, CareConnect or R4 so the choice of FHIR standard will be dependent on other factors, such as alignment with existing or parallel integration projects.

Projects at a discovery or early design phase should seek to implement against the R4 Core UK standard, unless identified partner systems are already available using STU3 or CareConnect and have incompatible timescales to migrate to R4 Core UK.

Using FHIR References

The method by which other FHIR resources, e.g. Medication or Patient, are referenced within the MedicationRequest will be a local implementation decision. There are three options;

  1. Referenced by URL to a FHIR Server
  2. Referenced by an identifier to a resource within the same FHIR Bundle
  3. Referenced by an identifier to a “contained” resource within the MedicationRequest resource

FHIR snippets using XML notation are as follows;

Using references by URL is the recommended / target solution where FHIR servers are available. These may be future nationally available FHIR servers or locally implemented FHIR servers. When referencing by URL it is recommended that the reference.display is populated with appropriate text as per the guidance within this document.

Where a FHIR server is not available or not used within an implementation, the reference by identifier within the same Bundle is the next recommended implementation option.

The use of a contained FHIR resource should be the last option considered. For resources like Patient this could introduce duplication within the complete FHIR payload. Also resource .text elements should then not be populated. This is because the resource is contained inside the MedicationRequest resource and all text should be represented in the MedicationRequest.text element, including data from the contained resource.

Tags: design

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