EDC (electronic data capture) is a type of software: the system where trial data is entered, validated and managed. eSource describes where an observation was first recorded: data initially recorded in electronic form. The two are not rivals. An EDC can hold data transcribed from paper, abstracted from an EHR, or entered directly as eSource.
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| Where first recorded | Entered in EDC by | Is the EDC entry source? | |
|---|---|---|---|
| Paper worksheet | Paper note | Transcription | |
| EHR or hospital record | The care record | Abstraction | |
| Direct entry in the eCRF | The eCRF itself | Entered at the visit | |
| ePRO diary | The participant’s answer | Submitted by the participant |
The direct answer
Definitions
Source data, in GCP terms, is the original record of an observation: the first place it was written down or captured. Source documents are the records that hold it, such as a clinic note, a lab report or a participant diary. eSource is the case where that first recording is electronic.
EDC refers to the system. It holds the case report form data a trial needs, checks it with rules and queries, keeps an audit trail and produces the dataset for analysis. For a fuller definition, see our what is EDC guide. An EDC is where the data lands; eSource is about how it got there and whether that landing is also the original.
If the EDC entry is a transcription, the monitor has to compare it with the original to confirm it is accurate. That comparison is source data verification, and it is a large share of monitoring effort. If the EDC entry is the original, there is no second record to compare, and verification shifts to confirming who entered it, when, with what permissions and that changes were controlled. The source data verification page covers the process in more depth.
Typical examples are values keyed straight into the eCRF at the visit, participant answers on an ePRO questionnaire, readings transferred electronically from a device, and EHR data used as source under defined conditions. Typical non-examples are a paper note typed up later, a PDF lab report whose result is copied into a form, or a photo of a worksheet.
Side by side
| EDC | eSource | |
|---|---|---|
| What it is | A type of software system | A characteristic of how data was first recorded |
| Question it answers | Where is the trial dataset held and cleaned? | Where was each value originally recorded? |
| Scope | The whole trial database | Individual data points or forms |
| Can exist without the other? | Yes: an EDC full of transcribed paper data | Needs an electronic system to record into, often an EDC or ePRO tool |
| Main benefit | Validation, queries, audit trail, analysis-ready data | No transcription step, time-stamped original entries |
| Main risk | Treating the EDC as source when it is a copy | Weak controls on who may enter data and how changes are tracked |
| What an inspector asks | Is the system validated and the data controlled? | Where is the original, and is it attributable and unchanged? |
| Linked concept | CRF, edit checks, queries, database lock | ALCOA principles, source data verification, certified copies |
The ALCOA data integrity principles (attributable, legible, contemporaneous, original, accurate) apply to source data whatever the medium. See the ALCOA+ checklist.
Data flows
A single study can use all three at once. The choice is made per data point and written in the study documents so that monitors and inspectors know where to look for the original.
Paper diary · week 3
Filled in when?
Digital diary · week 3
Every entry server-timestamped
Decision
Decide variable by variable, then write it into the monitoring plan or source data agreement.
Direct entry is a good candidate for eSource. Enter at the visit, with the audit trail as the history.
ePRO is eSource by design. The participant’s submission is the original.
The care record remains source. Enter values into the EDC and verify against it.
The original stays outside the EDC. Keep a certified copy and record the value in the eCRF.
Capture them electronically where the study supports it, and document how they enter the record.
Allowed if the protocol and source documentation say so. The EDC then holds transcribed data.
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Controls
Direct entry only works as source if the record can be trusted. In practice that means individual accounts, so every entry is attributable; time-stamped entries; an audit trail that records any later change with who, when and why; roles that limit who may enter or change data; and a way for the investigator to review and sign off. Our audit trail software page explains what a usable trail looks like, and the ALCOA+ checklist is a useful review tool.
A second point is retention and access. Source records must be available for inspection for as long as the rules require, and the investigator must keep control of them. A system where the sponsor holds the only copy of the original is a different risk. Check the protocol, the contracts and local regulations, and see paperless clinical trial site for how sites approach it.
Honest fit
Capture is a good fit: site staff enter at the visit, source data verification can be set per field, and every change is in a field-level audit trail.
Capture is a good fit: participants answer on their own phone through a link, with nothing to install.
Capture works alongside paper source: values are transcribed and the per-field verification setting tells monitors what to check.
Do not assume it. Capture has no EHR integration, and which wearables are configured is a per-study matter. Ask before relying on it.
The original stays outside the EDC whichever system you use. Capture records the value in the eCRF.
EDC is a system for entering, validating and managing trial data. eSource describes data that was first recorded in electronic form. An EDC can contain eSource data, transcribed data or both.
No. An EDC becomes eSource only for the data points that are entered directly as the first recording. If values are copied from paper or from another system, the original remains source and the EDC holds a copy.
Not the same, though they overlap. An eCRF is the electronic form. If a clinician or coordinator enters a measurement straight into the eCRF at the visit, that eCRF entry is eSource. If they copy from a note, it is not.
It changes it. With direct entry there is no second record to compare, so verification focuses on attribution, time stamps, permissions and controlled changes. For data that remains in outside records, verification still compares with the original.
FDA published final guidance on electronic source data in clinical investigations in 2013. It addresses data capture, who may enter data, and controls on electronic source. Check the current text on FDA’s website.
Yes. Many do. The protocol or source documentation should say which data points are recorded where, so monitors and inspectors know where each original lives.
Capture supports direct entry into the eCRF and ePRO questionnaires answered on the participant’s phone, with per-field source data verification and a field-level audit trail. Some originals, such as hospital lab reports, stay outside any EDC.
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Keep exploring
eSource for clinical sites
The site-level use case: record it once, where it happens.
EDC vs EHR
When the care record is the source.
Source data verification
Checking entries against the original.
ALCOA+ data integrity checklist
Review source data against the principles.
Paperless clinical trial site
Moving a site off paper source.
Capture EDC
Direct entry, per-field SDV and audit trail.
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