Module 5 · Part 2 · Data Architecture

Common Data Elements

Understand what Common Data Elements (CDEs) are, why they matter, and how to select and implement them to make your registry data maximally reusable.

Patient Registries 101 · Dr. Danielle Boyce · EpilepsyLive

What are Common Data Elements?

A Common Data Element (CDE) is a data element, a question, measurement, or variable, that has been precisely defined with
A standard definition of what is being measured
A standard set of permissible values or units
A standard name and code
Documentation of how it is collected
CDEs allow researchers to combine and compare data across registries, studies, and institutions.

Data pooling: If your registry uses the same CDEs as other registries in your disease space, your combined dataset is dramatically more powerful than either dataset alone.
Regulatory acceptance: FDA increasingly requires or strongly prefers CDEs from registries used to support drug development.
Industry partnerships: Pharmaceutical companies evaluating your registry for trial support will check whether your data elements align with established standards.
Publication: Journal reviewers evaluate data element choices.

The FDA and NIH jointly maintain the CDE Repository , the most important source for CDEs in US-based registries.
cde.nlm.nih.gov , Search by disease, research domain, or data element name.

The National Institute of Neurological Disorders and Stroke developed a comprehensive CDE framework now widely used across neurological disease registries.
Common Data Elements: Standards and Tools

PROMIS is an NIH-developed library of validated patient-reported outcome measures covering physical, mental, and social health.
Key PROMIS domains for rare disease registries
Physical Function
Fatigue
Pain Interference and Pain Intensity
Sleep Disturbance

Divide your data elements into
Core elements: Required for all participants at enrollment and each follow up. Keep this list short, every additional required element reduces completion rates.
Supplemental elements: Collected when available, or for specific subpopulations (e.g., genetic data only for participants who consent to genotyping).
Time-stamped longitudinal elements: Collected at defined intervals to track disease progression.

A common mistake: collecting too many data elements.
Design principle: What is the minimum set of data elements that answers your core scientific questions?
A well-designed rare disease registry often has
15 to 30 core enrollment elements
5 to 10 core follow up elements (collected every 6 to 12 months)
20 to 50 supplemental elements (collected once or as available)

[ ] Each element is documented with definition, type, permissible values, and source
[ ] Pilot-tested questionnaire for completion time and participant comprehension