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RADx® MARS: HL7v2 vs FHIR

HL7 Standards Landscape

HL7v2 Pros and Cons:

The HL7v2 Messaging standard has been used for communicating laboratory data for decades. The v2 base standards are in “maintenance” mode according to HL7. While reliable and common, there are known limitations of v2; for example, there is no underlying information model, optionality is ubiquitous, and there is poor support for controlled vocabularies. Nevertheless, HL7v2 supports the simple fields needed for communication of at-home test results to public health agencies. All state, local, and territorial health agencies support the V2 standard, whereas few, if any, can accept FHIR messages at this time. 

The HL7 version 2.5.1 Implementation Guide, Electronic Laboratory Reporting to Public Health, Release 2 (US Realm) from 2014, was examined to support the identification of v2 fields for the RADx MARS HL7v2 specification.

FHIR Pros and Cons:

Fast Health Interoperabilty Resources (FHIR) is HL7’s newest standard. FHIR has been rapidly developed and adopted with much enthusiasm from standards designers, developers, and implementers because it is easily implemented and has a lower bar for developers. It is flexible; base resources can be used as is or adapted as needed.

When coupled with Substitutable Medical Applications, Reusable Technologies (SMART) APIs, apps for any use case can be rapidly developed and implemented. Once built, apps can be launched across many health systems. These apps are/can be both patient or provider facing: Patients from different health systems can use a consumer single app, or providers can use a business app running within the EHR with minimal modifications.

FHIR app functions can be seamlessly launched directly from EHRs, even those developed externally to the EHRs. There are some negotiations and agreements to be made with the EHRs, but this will likely become easier over time especially with information blocking rules. Most importantly for this use case, FHIR apps have a great future for patient data access and patient empowerment.

FHIR does have limitations. It provides a generic structure for communicating data which requires specific constraint for different use cases. The same data mapping and terminology implementation and maintenance challenges exist as exist with Consolidated Clinical document Architecture (C-CDA) and V2. In addition, although FHIR has been implemented across all major EHRs, the degree to which FHIR supported functions are generally available in implemented (sold) EHR software is variable and not fully known. Furthermore, public health systems are generally unable to accept FHIR messages at this time.

References