Message Specification

Overview

The Pathology FHIR Specification defines a set of HL7 FHIR profiles and guidance to support the electronic exchange of pathology laboratory data. The current focus is on the use of the specification for pathology test reporting however aspects of test requesting are also supported.

Development of the specification was informed by the creation of a logical data model called the Pathology Information Model. The relationship between the Pathology Information Model and the Pathology FHIR Specification is described below.

Purpose

The initial priority is to use the Pathology FHIR Specification to replace the PMIP EDIFACT specification (Pathology Messaging Implementation Project - Electronic Data Interchange for Administration, Commerce and Transport).

The PMIP EDIFACT specification defines the structure of test reports that flow between pathology laboratories and GP practices. It is used in conjunction with the Read code based PBCL (Pathology Bounded Code List). As described elsewhere, the replacement for the PBCL is the UTL (Unified Test List).

Pathology Information Model

The Pathology Information Model provides a logical, business-level representation of the information relating to pathology test reporting. It consists of:

  • a tabular definition of pathology related business entities (Specimen, Test Result, Patient etc.) and their associated data elements (Specimen.identifier, Specimen.type, Specimen.status etc.)
  • a diagram that illustrates the relationships between the business entities

A copy of the model is available to download here

The Pathology Information Model was used as a key input into the development and curation (via INTEROPen) of a set of draft HL7 FHIR STU3 CareConnect profiles and supporting Implementation Guide. A set of draft HL7 FHIR R4 profiles (part of the FHIR UK Core initiative) and Implementation Guide have also been developed. These are described in the Pathology FHIR Specification section below.

Pathology Information Model to FHIR Profile Mapping

As part of the development of the Pathology FHIR Specification, the business entities described in the Pathology Information Model were mapped to corresponding FHIR profiles. This mapping is summarised below:

  • Test Request Summary - this business entity contains information relating to the requested test(s). It maps to the ProcedureRequest FHIR STU3 profile. In FHIR R4 it maps to the ServiceRequest profile.
  • Test Report - this business entity contains the overall findings and clinical interpretation of one or more test results. It maps to the DiagnosticReport FHIR profile.
  • Specimen - this business entity contains details of the specimen(s) provided for testing. It maps to the Specimen FHIR profile.
  • Test Group - this business entity is used to define a group of related tests, for example a Full Blood Count. Test groups are often referred to as batteries, panels or profiles. It maps to the Observation FHIR profile. 
  • Test Result - this business entity contains information relating to a single test result. It maps to the Observation FHIR profile. Note: Multiple levels of Test Groups and Test Results may be nested to support complex report structures, such as those used in Microscopy, Culture and Sensitivity reports.

The business entities representing the Requester / Requesting OrganisationPerformer / Performing Organisation and Specimen Collector / Specimen Collecting Organisation map to the Practitioner and Organization FHIR profiles respectively. The Patient business entity maps to the Patient FHIR profile.

The high-level relationship between the business entities and corresponding FHIR profiles is illustrated in the following diagram:

pathology-information-model USE this one

To aid clarity, individual and organisation type entities (e.g. Performer / Performing Organisation) have been combined in the diagram but may be referenced independently.

Pathology FHIR Specification

The Pathology FHIR Specification comprises the FHIR profiles outlined above and an Implementation Guide. The Implementation Guide defines any additional constraints and rules that should be applied to the profiles and also includes a description of the messaging architecture and example messages.

Two draft versions of the profiles and Implementation Guide are currently available, for FHIR STU3 and FHIR R4. The following table provides a summary with links to the relevant artefacts:

Item

 Pathology FHIR STU3

 Pathology FHIR R4

Implementation Guide

Pathology FHIR STU3 Implementation Guide

Pathology FHIR R4 Implementation Guide

Pathology Profiles

DiagnosticReportObservationProcedureRequestSpecimen

DiagnosticReportObservationServiceRequestSpecimen

Common Profiles

OrganizationPatientPractitioner

OrganizationPatientPractitioner

The following diagram provides a detailed description of the relationship between each of the FHIR profiles (note: the arrows represent the direction of the references between the profiles):

pathology-fhir-model USE this one

Microbiology Reporting

The following presentation slides outline the proposed design approach for supporting Microbiology reports using the Pathology FHIR STU3 profiles: Presentation Slides (download)

The slides reference the following example FHIR STU3 message (for a Microscopy, Culture and Sensitivity report): Example FHIR Message (download)

Additional Use of the Pathology Related FHIR Profiles

In addition to their use as part of the Pathology FHIR Specification, the pathology related FHIR STU3 profiles are also used by several other NHS Digital projects and programmes. These are summarised below.

EDIFACT-FHIR Lab Results Adaptor: this provides a way for GP systems to receive EDIFACT (NHS003) based lab test result messages using a FHIR interface. Further details can be found here

GP Connect: a GP Connect variant of the pathology related CareConnect FHIR STU3 profiles are used to support the retrieval of pathology lab results from GP systems. This forms part of the GP Connect Access Record Structured FHIR API. Further details can be found here and here