Short Description

The primary focus is exchange of complex cohort definitions (eligibility criteria, inclusion and exclusion criteria) for research cohorts, clinical trials, clinical care recommendations, and clinical quality measure population definitions. 

Long Description

The use of FHIR to express eligibility criteria has been limited. Using the characteristic backbone element of the Group resource to express criteria has been the suggested approach but has limitations for complex criteria, including inability (without a separate expression language) to express combinations (any of, at least n, at most n) of criteria, modifications of criteria (e.g. method of determination), and timing of criteria with respect to specified events.

The Evidence-Based Medicine on FHIR project group (co-sponsored by CDS, CQI and BRR WGs) developed EvidenceVariable Resource to express complex characteristics defining evidence variables. With BRR, multiple examples were demonstrated to confirm the expressivity of complex eligibility criteria for clinical trials.

Recently, the recognition of the need for standard methods to express individual characteristics for findability, re-usability, and interoperability across cohort definitions (eligibility criteria, inclusions/exclusion criteria, phenotypes, quality measures, prior authorization, etc.) and across developers of cohort definitions (e.g. searching a library of characteristics for re-use) led to a Characteristic FHIR Resource Proposal.

In this Connectathon Track, we will introduce these developments, demonstrate the use of EvidenceVariable.characteristic element (and the proposed Characteristic Resource) to structure cohort definitions, and help participants apply these resources to fit cohort definitions of interest.


Test the design of a Resource/set of Resources

Related Tracks?

Clinical Reasoning, 

Call for participants

Clinical trial, Clinical Decision Support, Quality Measure and Quality Improvement system developers with attention to creating or interpreting cohort definitions (inclusion/exclusion criteria, eligibility criteria, phenotypes)

Track Prerequisites


Track Lead(s)

Track Lead Email(s);

Specification Information

Current Build version of FHIR

Track planning meetings include:

  • BRR (Eligibility Criteria for Clinical Trials Project) meetings on Thrusdays (12 pm Eastern) at Zoom Meeting
  • CDS sub-Work Group LHS Connectathon Coordination meetings on Thursdays (1 pm Eastern) at Zoom Meeting
  • HEvKA Eligibility Criteria Working Group meetings on Fridays (noon Eastern) at Teams Meeting

Zulip stream

Track Kick off Call

April 27, Thursday, at 1-2 pm Eastern Time

Call Info:

Phone: +1 646-558-8656, Participant Code: 209 701 8272

Webmeeting Info:

Join Zoom Meeting

Meeting ID: 209 701 8272

Password: 343027

One tap mobile

+16465588656,,2097018272# US (New York)

+16699009128,,2097018272# US (San Jose)

Testing Scenario:

System roles:

Cohort Definition Content Creation/Editing

Cohort Definition Content Viewing (human-readable interpretation)

Cohort Definition Content Machine Interpretation (conversion to computable expression)

Repository of 'Cohort Definition Characteristics'


Expressing Cohort Definitions


Express complex cohort definitions using EvidenceVariable Resource.

Examples of complex cohort definitions include:

Success Criteria:  

Track participants are able to express cohort definitions with satisfactory degree of granularity.

Bonus point:

Track participants are able to interpret cohort definitions expressed by other participants.

TestScript(s): None

Security and Privacy Considerations: None


Finding Cohort Definition Characteristics


Find pre-existing characteristics to re-use in creating complex cohort definitions using EvidenceVariable Resource.

Success Criteria:  

Track participants are able to search a repository of 'Cohort Definition Characteristics' and find specific characteristics.

Bonus point:

Track participants are able to use the found characteristics in the expression of new cohort definitions.

TestScript(s): None

Security and Privacy Considerations: None