The ResearchElementDefinition resource describes a "PICO" element that knowledge (evidence, assertion, recommendation) is about.

ResearchElementDefinition
url
Canonical identifier for this research element definition, represented as a URI (globally unique)
identifier
Additional identifier for the research element definition
version
Business version of the research element definition
name
Name for this research element definition (computer friendly)
title
Name for this research element definition (human friendly)
shortTitle
Title for use in informal contexts
subtitle
Subordinate title of the ResearchElementDefinition
status
draft | active | retired | unknown
experimental
For testing purposes, not real usage
subject[x]
E.g. Patient, Practitioner, RelatedPerson, Organization, Location, Device
date
Date last changed
publisher
Name of the publisher (organization or individual)
contact
Contact details for the publisher
description
Natural language description of the research element definition
comment
Used for footnotes or explanatory notes
useContext
The context that the content is intended to support
jurisdiction
Intended jurisdiction for research element definition (if applicable)
purpose
Why this research element definition is defined
usage
Describes the clinical usage of the ResearchElementDefinition
approvalDate
When the research element definition was approved by publisher
lastReviewDate
When the research element definition was last reviewed
effectivePeriod
When the research element definition is expected to be used
topic
The category of the ResearchElementDefinition, such as Education, Treatment, Assessment, etc.
author
Who authored the content
editor
Who edited the content
reviewer
Who reviewed the content
endorser
Who endorsed the content
relatedArtifact
Additional documentation, citations, etc.
library
Logic used by the ResearchElementDefinition
type
population | exposure | outcome
variableType
dichotomous | continuous | descriptive
characteristic
What defines the members of the research element
definition[x]
What code or expression defines members?
usageContext
What code/value pairs define members?
exclude
Whether the characteristic includes or excludes members
unitOfMeasure
What unit is the outcome described in?
studyEffectiveDescription
What time period does the study cover
studyEffective[x]
What time period does the study cover
studyEffectiveTimeFromStart
Observation time from study start
studyEffectiveGroupMeasure
mean | median | mean-of-mean | mean-of-median | median-of-mean | median-of-median
participantEffectiveDescription
What time period do participants cover
participantEffective[x]
What time period do participants cover
participantEffectiveTimeFromStart
Observation time from study start
participantEffectiveGroupMeasure
mean | median | mean-of-mean | mean-of-median | median-of-mean | median-of-median