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, 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. As the development of CA:FeX continues, the Interoperability Specifications may evolve into a more formal Integration Profile (similar to existing international profiles reviewed below) that provides more comprehensive guidance on FHIR RESTful exchange patterns than what currently exists today.

It should be noted that the scope of CA:FeX may evolve beyond document-based exchange to explore a more atomic nature of health information exchange in the future. This will depend on the development of a multi-phased CA:FeX roadmap, the evolving needs of the Canadian healthcare market, and emerging trends within the international FHIR health information exchange community.

Upon review of legacy IHE profiles, 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. Below highlight the two key existing IHE profiles that were contemplated with some of their limitations:

• 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.
• Mobile access to Health Documents (MHD): This IHE profile is designed for the utilization of FHIR syntax to communicate and exchange documents, including, as an option, acting as a proxy to systems that use XDS. MHD leverages FHIR resources (i.e., 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 (i.e., XDS infrastructure, FHIR, or another storage system) the profile applies constraints to the FHIR DocumentReference resource. The current limitation of MHD, however, requires that a document is submitted in FHIR Binary format and does not include the use of a FHIR Bundle (of type Document) to represent documents. Further, MHD entails a multi-step document retrieval process (list/find step followed by the 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 driven FHIR Implementation Guides that include document exchange (e.g., US Core, IPA, PACIO, IPS, etc.) have begun utilizing a pattern, leveraging the DocumentReference Resource. 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. 

Within the context of the Canadian market, there is an indication that the level of readiness for exchange patterns outlined by international FHIR Implementation Guides, such as the US Core, may not be appropriate for implementers in the current state. As such, simpler exchange patterns are also a viable alternative. One such alternative is narrowing the focus to the exchange of non-binary documents and utilizing the appropriate FHIR Search Parameters and FHIR Operations based on the Composition Resource to search and retrieve documents. 

Given the preliminary findings, both internationally and domestically, CA:FeX outlines the use of FHIR Search and FHIR Operations based on both (i) the DocumentReference Resource and (ii) the Composition Resource. While these methods are surfaced by CA:FeX to drive adoption and feedback, this is still being tested and addressed by the FHIR document exchange community. Furthermore, the current methods explored by this version of CA:FeX do not represent the only FHIR methods available to enable document exchange or, more broadly, health information exchange as a whole. As international specifications mature and the Canadian market evolves, CA:FeX will dig deeper into the more sophisticated alternatives for health information exchange in order to guide the Canadian market in the same direction.

Due to the continuous development of the market, there will be an opportunity to encompass a broader set of use cases that may deal with the exchange of more atomic information going forward.

In parallel with CA:FeX, Canada Health Infoway is also facilitating a national collaborative effort to develop 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 Reference Architecture will reference the CA:FeX Interoperability Specifications as an optional implementation pattern for submitting, searching and retrieving a Patient Summary document.

Context

The pan-Canadian CA:FeX Interoperability Specifications are published to a public space within Canada Health Infoway’s InfoScribe and is 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 pan-Canadian 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.
• 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 in the Reference Architecture section. 
• CA:FeX Actor Conformance: Establishes the Actor Conformance Requirements for the CA:FeX Interoperability Specifications.
• Privacy & Security Guidance: Provides a link to a Digital Health Privacy Toolkit that is under development and describes key Security considerations 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.

Document Conventions 

The pan-Canadian CA:FeX Interoperability Specifications will be numbered according to this format:

• Name + Version + Stage, where name refers to the name of the document, version refers to the versioning history of the document and stage refers to its stage in implementation such as “Trial Implementation” or “TI”.
• Key documents will evolve during review cycles from version 0.x to v1.0.

Requirements Language

The following conventions are used to specify requirement levels for the business requirements of the pan-Canadian 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 pan-Canadian CA:FeX Interoperability Specifications document has been developed based on international research and stakeholder consultations with HIE Subject Matter Advisors, where this was socialized and validated with the leading 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 pan-Canadian 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 will include a multi-stage review and feedback process, as documented here.