Preface

The CA:FeX Interoperability Specifications (Canadian FHIR Exchange (CA:FeX)) seek to promote FHIR RESTful exchange patterns, developed by industry-leading FHIR standards that can be applied on top of an existing infrastructure just as easily as it can be applied on top of FHIR servers. 

The current version of CA:FeX is focused on the FHIR RESTful exchange of documents as well as individual resources, which FHIR offers multiple structures and patterns to achieve. CA:FeX aims to provide clarity to implementers by identifying some of the choices currently available using FHIR, ranging from simple to a higher level of sophistication. The scope of CA:FeX will continue to evolve to support a multi-phased CA:FeX roadmap, the evolving needs of the Canadian health care market, and emerging trends within the international FHIR health information exchange community.

CA:FeX seeks to harmonize around global interoperability guidance and well-implemented exchange patterns. For this reason, CA:FeX attempts to identify any established IHE profiles that align to its use cases and requirements. Ideally, these IHE profiles can be implemented directly. However, localization is sometimes needed when legacy profiles do not meet Canadian requirements or when the requirements of legacy profiles need to be further refined to better meet implementer needs.

Upon review of legacy IHE profiles for document exchange, existing guidance is either based on the enablement of document sharing within non-FHIR infrastructures or through the narrow use of FHIR resources. Given the evolving needs of the Canadian market, these legacy profiles may not be entirely sufficient to enable the FHIR RESTful exchange of documents. Two key existing IHE profiles that were contemplated, including some of their limitations, are listed below:

• Cross-Enterprise Document Sharing (XDS): This IHE profile is focused on providing a standards-based specification for the sharing of documents which is limited to non-FHIR infrastructures. Note that, although considered, the XDS profile is not presented as an option within the Reference Architecture, as the Canadian landscape revealed that it is interested in adopting more modern FHIR-based approaches.
• Mobile access to Health Documents (MHD): This IHE profile is designed for the utilization of FHIR standard to communicate and exchange documents, including, as an option, acting as a proxy to systems that use XDS. MHD leverages FHIR resources (i.e., List, DocumentReference) as a standard method for clients to find a document. To ensure this IHE profile can be used without regard for how information is stored (e.g., XDS infrastructure, FHIR, or another storage system) the profile applies constraints to the FHIR List resource and the DocumentReference resource. MHD entails a multi-step document retrieval process (find List, followed by find DocumentReference step, followed by the document retrieval step) which may not be the single approach implementers will take going forward.

Through a market scan, it was observed that in line with MHD, existing RESTful FHIR Implementation Guides that include document exchange (e.g., US Core, IPA, PACIO, IPS, etc.) have begun utilizing a pattern, leveraging the DocumentReference Resource and/or the $docRef operation. These Implementation Guides, however, enable querying in a single way and return pointers to document content, wherever it is stored and irrespective of the format (e.g., binary or FHIR-assembled). FHIR Search Parameters and FHIR Operations have been developed to augment the capabilities of this pattern to more easily get back what was requested and enable the offering of documents in the expected format without having to change the underlying data model / document and lifecycle practices. 

Earlier versions of the CA:FeX specification focused on exploring simpler exchange patterns for submitting and retrieving FHIR documents (from FHIR Document Repositories) using the appropriate FHIR Search Parameters based on the Bundle and Composition Resources. This version expands on that scope to highlight emerging patterns for using DocumentReference Resource and FHIR Operations to find and retrieve documents from Hybrid Document Repositories (i.e., repositories that include a mixture of document types and formats). This still represents a simpler approach (compared to MHD) by removing the requirement for a List resource. As more is known from the trialing of this pattern, it will be assessed for potential refinement of the MHD profile. 

This version also includes foundational expectations for exchanging atomic data (individual FHIR resources). The initial use cases involving the exchange of atomic data were well aligned to the IHE Query for Existing Data for mobile (QEDm) profile and may not require further changes to be proposed to QEDm. 

The intent of CA:FeX is to support exchange behaviors in pan-Canadian specifications like the pan-Canadian Patient Summary Interoperability Specifications (PS-CA), an implementable, testable specification, based on the IHE International Patient Summary specification and the HL7 IPS Implementation Guide. The PS-CA references the CA:FeX Interoperability Specifications as an optional implementation pattern for submitting, searching and retrieving a Patient Summary document. As pan-Canadian specifications increase, particularly ones that rely on exchange of individual FHIR resources, utilization of CA:FeX is also expected to evolve. 

Context

The CA:FeX Interoperability Specifications are published to a public space within Canada Health Infoway’s InfoScribe and are also available as a downloadable document, here.  InfoScribe is a web-based tool developed for jurisdictions and vendors to create, publish, and collaborate on clinical requirements and specifications for interoperability solutions. Teams can document, share, and discuss content, files, ideas, specs, mock-ups, diagrams, and projects. A link to the online published content and the downloadable documentation will be published with each release of CA:FeX. 

Introduction to IHE 

Integrating the Healthcare Enterprise (IHE) is an international initiative to promote the use of standards to achieve interoperability among health information technology (HIT) systems and effective use of electronic health records (EHRs). IHE provides a forum for care providers, HIT experts and other stakeholders in several clinical and operational domains to reach consensus on standards-based solutions to critical interoperability issues.

The primary output of IHE is system implementation guides, called IHE profiles. IHE publishes each profile through a well-defined process of public review and Trial Implementation and gathers profiles that have reached Final Text status into an IHE Technical Framework. 

How to Read This Document 

This document contains the following sections: 

Within the Pan-Canadian CA:FeX Interoperability Specifications, you can expect the following subsections:

• Introduction & Preface: Contains an introduction to the CA:FeX Interoperability Specifications. This section contains a summary of the context, document purpose and scope, as well as other content to help orient the first-time reader to the topic of these specifications and how they relate to other specifications in the digital health ecosystem in Canada.
• Privacy & Security Guidance: Provides a reference to Infoway's recently published privacy primer, Privacy as an Enabler, that provides an introduction to interoperability, an overview of Canadian privacy laws and some practical approaches to privacy for interoperability. And, it provides a high-level list of security considerations for the CA:FeX specifications.
• Use Case Overview: Describes the Use Cases, including design constraints and assumptions and the flows of information that will be specified in the CA:FeX Interoperability Specifications. This section also references scenarios that describe how the specified flows may be used in the Canadian context.
• Core Interoperability Specification Requirements: Establishes the Core Interoperability Requirements for the CA:FeX Interoperability Specifications with respect to a FHIR Health Information Exchange (HIE) implementation pattern. This section also provides mapping of use case actors to the technical actors of the CA:FeX Interoperability Specifications and the services they are supporting, which are aligned with the flow captured in the sequence diagrams included here.
• CA:FeX Actor Conformance: Establishes the Actor Conformance Requirements for the CA:FeX Interoperability Specifications.
• CA:FeX Actors and Transactions: Illustrates the abstracted actors and transactions in scope for the CA:FeX Interoperability Specifications.
• CA:FeX Sequence Diagrams:  Provides guidance on how to apply CA:FeX implementation patterns along with other IHE profiles to address interoperability needs pertaining to FHIR Health Information Exchange (HIE) implementation pattern.  They group together actors and transactions from multiple profiles including CA:FeX to address the scope of the use cases.
• CA:FeX Cross Profile Considerations: Provides guidance on groupings between the CA:FeX actors with other IHE profiles to achieve additional functionality such as Network Security, Authentication, Authorization, Auditing and more.
• CA:FeX Audit Considerations: Provides audit considerations for each of the CA:FeX transactions.

Document Conventions 

The CA:FeX Interoperability Specifications will be versioned according to the IO Specifications Publication Model, defined here.

Requirements Language

The following conventions are used to specify requirement levels for the business requirements of the CA:FeX Interoperability Specifications:

• Shall: used to indicate a required requirement.
• Should: used to indicate that a requirement is recommended and should be considered as best practice for implementation, but not required  (i.e., it is optional) for implementation.
• May: used to indicate that a requirement is permittable / optional, but not required  for implementation.
• Shall not: used to indicate that an element or action is prohibited.

Additional information on the CA:FeX business requirements can be found in the Use Cases and Definitions section.

Methodology

The CA:FeX Interoperability Specifications have been developed based on international research and stakeholder consultations with HIE Subject Matter Advisors, where this was socialized and validated with participating jurisdictions and vendors through Coordinating Table Meetings, Executive Table Meetings, stakeholder workshops and 1-on-1 meetings to further refine the specifications.

Introduction to a Use-Case Driven Approach

The following use case-driven approach was utilized in the development of the CA:FeX Interoperability Specifications:

• Baseline: Develop foundational Use Cases, Use Case Scenarios and Business Requirements for FHIR Health Information Exchange (HIE).
• Collaborate: Collaborate with jurisdictions, clinical SMEs, technical SMEs, vendors, participating organizations to develop and refine detailed artefacts.
• Review: Review and provide feedback into artefacts through engagement workshops and input gathering.
• Publish: Publish artefacts for broader stakeholder consultation.
• Recommend: Recommend draft artefacts for approval.
• Iterate: Continue to refine as per testing and priorities.

Release Cycle

The CA:FeX Interoperability Specifications' release cycle includes a multi-stage review and feedback process, as documented here.