eSource (Electronic Source Data)

eSource (electronic source data) is clinical trial data that originates in electronic form — that is, the electronic record is the first place the observation was ever recorded — rather than being written on paper first and later transcribed into an electronic system. A vital sign typed directly into the study’s EDC system during the visit is eSource; the same vital sign written on a paper vitals sheet and later keyed into that EDC system by a data entry clerk is not, because the EDC entry in that case is a transcription, not the original record. The distinction is about where the data was born, not which software eventually holds it.

eSource vs. EDC vs. eCRF: three related but distinct things

These terms get used interchangeably in casual conversation but describe different layers of the same workflow, and the difference matters for data integrity planning:

• Electronic Data Capture (EDC) is the software platform used to capture, store, and manage study data — see CASRAI’s Electronic Data Capture (EDC) term. An EDC system can hold eSource data, transcribed (non-eSource) data, or both within the same study.
• An eCRF is the electronic form inside an EDC system that structures how data is entered for a given visit or assessment — see CASRAI’s Case Report Form (CRF) term. Whether the data typed into an eCRF counts as eSource depends entirely on whether that entry is the first recording of the observation or a transcription from an earlier paper source document.
• eSource is a property of the data itself — its origination point — not a system or a form. Data can be eSource whether it lands in an EDC eCRF, an EHR, or a standalone eCOA/ePRO device.

In short: EDC is the platform, eCRF is the form, eSource is a statement about where a specific data point was actually created.

Common eSource types

FDA’s guidance on electronic source data describes several ways clinical data can originate electronically:

• Direct EHR capture: a clinician documents an observation (a diagnosis, a physical exam finding, a medication administered) directly into the participant’s electronic health record during routine or study-related care, and that EHR entry — not a separate paper note — is the original record.
• eCOA / ePRO: electronic clinical outcome assessments and electronic patient-reported outcomes, where a participant or clinician enters an assessment directly into a study device, tablet, or app, with no paper form completed first.
• Direct EDC entry: site staff type an observation straight into the study’s EDC system at the point of collection — during the visit, at the bedside, or immediately after an assessment — rather than onto an interim paper worksheet.
• Instrument or device feed: data captured automatically from a connected device (an ECG machine, a lab analyzer, a wearable sensor) and transmitted directly into the study record without manual paper transcription in between.

Why the distinction matters

Two related reasons drive why sponsors, monitors, and regulators care whether data is eSource rather than transcribed:

• Transcription error reduction. Every manual transfer of a value from one medium to another — paper to EDC, one system to another — is a point where a digit can be mistyped, a unit misread, or a field skipped. Capturing data electronically at its origin removes that intermediate step entirely for that data point.
• Supporting ALCOA+ data integrity. Regulators expect clinical trial data to be attributable, legible, contemporaneous, original, and accurate, plus complete, consistent, enduring, and available (the ALCOA+ attributes FDA and MHRA guidance describe). Data entered directly at the point of observation is inherently more contemporaneous and more clearly “original” than a paper record that sits for a period before someone transcribes it — and a well-validated electronic system preserves the audit trail (who entered what, when, and any subsequent change) automatically, which a paper-then-transcribe workflow has to reconstruct manually across two documents instead of one.

None of this means eSource data is exempt from monitoring or verification — see CASRAI’s Case Report Form (CRF) term for how source data verification (SDV) works. It means the “source document” being verified against, for eSource data, is the electronic record itself (or a certified copy of it), not a paper original.

Regulatory basis

FDA’s September 2013 guidance for industry, Electronic Source Data in Clinical Investigations, defines electronic source data as data initially recorded in electronic format, and sets expectations for sponsors, CROs, and investigators around capturing, reviewing, and retaining that data so that it remains reliable, attributable, and traceable from the point of electronic capture through to electronic regulatory submission. The guidance’s underlying goal was to encourage sponsors to move away from paper-then-transcribe workflows where practical, since a properly designed eSource workflow can reduce transcription burden at sites while strengthening the audit trail regulators rely on during inspection. ICH E6, which defines source data and source documents more broadly and underpins CRF design and source data verification generally, sits alongside this FDA-specific guidance — see CASRAI’s ICH E6(R2) term.

Related CASRAI content

For how eSource data flows through a study’s broader data management process — including EDC system selection, database lock, and retention — see CASRAI’s guide, Data Management Plan for Clinical Trials: EDC, CRF Flow, Lock & Retention. For the electronic records and signatures requirements that apply once source data is captured electronically, see CASRAI’s 21 CFR Part 11 term.