eCOA (electronic clinical outcome assessment) is the umbrella for every outcome measure collected electronically: reported by the patient, a clinician, an observer, or built from a task the patient performs. ePRO is the first of those, the part the patient reports directly. Most trials that say they need eCOA mean ePRO plus some site-rated scales.
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| Type | Reported by | Under eCOA? | Under ePRO? | |
|---|---|---|---|---|
| PRO | The participant | |||
| ObsRO | A caregiver or observer | |||
| ClinRO | A clinician | |||
| PerfO | A standardised task |
The direct answer
Definitions
A clinical outcome assessment is a measure of how a patient feels, functions or survives, used as evidence of a treatment effect. The FDA-NIH BEST glossary groups COAs by who provides the information, which is the grouping the field uses. Critical Path Institute’s eCOA consortium material describes eCOA as the electronic capture of those assessments, which can be delivered on smartphones, tablets, web browsers and, increasingly, sensor-based tools.
ePRO is narrower. It is the electronic collection of patient-reported outcomes: information that comes directly from the participant, without interpretation by a clinician or anyone else. That is the symptom diary, the weekly fatigue scale, the quality-of-life questionnaire. Our what is ePRO guide covers the concept in depth, and the eCOA glossary entry is the short definition. This page is the comparison and the decision.
PRO is completed by the participant about their own condition: pain intensity, sleep, mood, symptom frequency. ClinRO is completed by a trained clinician after observing or examining the participant, such as a severity rating at a visit. ObsRO is completed by a non-clinician observer, typically a parent or carer, when the participant cannot report reliably, as in paediatric or cognitive studies. PerfO is based on the participant performing a standardised task, such as a timed walk or a cognitive test, scored by a rater or device. The PRO, ClinRO, ObsRO and PerfO glossary entry goes through each.
Putting an assessment on a screen changes how it is administered, not what it measures. That is the useful lens: eCOA and ePRO describe a delivery mode, and the underlying instrument keeps its meaning only if the screen version faithfully reproduces the paper one. Layout, scale display, recall period and wording all matter.
Side by side
| eCOA | ePRO | |
|---|---|---|
| What it is | Umbrella for all electronically collected clinical outcome assessments | The patient-reported subset of eCOA |
| Who completes it | Participant, clinician, caregiver or observer, or the participant doing a task | The participant only |
| Where it is completed | At home, in the clinic or both | Usually at home or on the participant’s own device, sometimes in clinic |
| Typical instruments | Symptom diaries, clinician rating scales, caregiver reports, timed tests | Symptom diaries, quality-of-life and symptom questionnaires |
| Typical timing | Scheduled diaries plus visit-based assessments | Daily or weekly diaries and visit-based questionnaires |
| Main risks | Different respondents, different training and rater consistency | Missed entries, late entries and recall bias |
| What buyers mean by it | A broader platform brief, or sometimes just ePRO under another label | A patient-facing questionnaire or diary tool |
| Regulatory emphasis | Instrument fit for purpose, whoever completes it | FDA PRO guidance (final, 2009) emphasises instrument development and, for electronic instruments, investigator access to the source records |
Check the exact terms your regulator, sponsor or protocol uses before writing an RFP.
In Capture
Capture lets each assessment in the schedule record who completes it. Participant questionnaires run on the participant’s phone or a clinic tablet through a link, with nothing to install. Assessments completed by site staff are built as site forms in the same study, and the same audit trail covers all of them.
Patient-reported
Participant, own phone
Observer-reported
Caregiver
Clinician-reported
Site staff, clinic tablet
Performance outcome
Site-run test, e.g. chair rise
Decision
Answer these from the protocol’s schedule of assessments.
You need ePRO. Look for questionnaire scheduling, reminders and completion tracking.
You need eClinRO capability too: a way for site staff to complete and sign assessments in the same study record.
You need ObsRO: a separate respondent, a clear instruction for who may complete it and a way to record who did.
You need PerfO capability: site or device-administered tasks with a defined procedure and rater.
Treat it as ePRO. Do not buy a broader platform than the schedule needs.
Check the rights holder’s terms for electronic use before you build, whichever label applies.
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Buying
Vendors position products on both sides of this line. A pure ePRO product is optimised for participant-facing diaries and questionnaires. A full eCOA product also handles clinician and observer respondents, and may include device provisioning and rater workflows. A platform that includes EDC, ePRO and eConsent together, which is Capture’s model, collapses some of the integration questions because site forms and participant questionnaires land in one study database. If you are scoping a purchase, see best eCOA platforms and best ePRO software for how to compare vendors, and ePRO software for clinical trials for the participant-facing feature set.
The question to ask is not "eCOA or ePRO" but "who completes which assessment, where, and how often". Write that into the brief. It prevents two mistakes: paying for respondent types you do not have, and discovering at set-up that a clinician-rated scale has no home.
Honest fit
Capture is a good fit: no app to install, scheduled tasks, reminders, completion windows and a compliance view.
Capture is a good fit: they are built as site forms next to the ePRO tasks, with one audit trail.
Possible, but the licence stays your responsibility. Capture records licence details on participant questionnaires and does not verify licences or supply instrument wording.
Not what Capture is. If your protocol demands that, a specialist eCOA vendor is the better fit.
eCOA is the electronic collection of any clinical outcome assessment: patient-reported, clinician-reported, observer-reported or performance-based. ePRO is only the patient-reported part. ePRO is a subset of eCOA.
Not strictly, although the terms are often used interchangeably because patient-reported data is the most common eCOA type. If a protocol includes clinician ratings or caregiver reports, those fall under eCOA but not ePRO.
Patient-reported outcome (PRO), clinician-reported outcome (ClinRO), observer-reported outcome (ObsRO) and performance outcome (PerfO). When collected electronically, they are all eCOA.
It depends on who completes your assessments. If every outcome is reported by participants, ePRO software is enough. If you also have clinician ratings, caregiver reports or performance tasks in the schedule, you need a platform that supports those respondents too.
Yes. Capture runs participant questionnaires and site-completed assessments in the same study, with a shared audit trail. Check that the respondent types in your schedule are all supported before you commit.
It can. Layout, wording, scale presentation and recall period should stay faithful to the original, and some instruments have specific rules and licence terms for electronic use. Check the rights holder’s terms.
No. A study team can record licence number, holder and expiry on a participant questionnaire, and Capture warns staff before expiry and stops new collection after it. Capture does not verify licences with rights holders or supply licensed instruments.
Yes. The free sandbox includes every feature with sample data, no credit card and no time limit. You pay only when you go live with real participants.
Keep exploring
eCOA software for clinical trials
How Capture handles each respondent type.
What is ePRO? A plain-English guide
The ePRO concept in depth.
eCOA glossary entry
The short definition and related terms.
Best eCOA platforms
How to compare eCOA vendors.
ePRO vs paper diaries
The other common ePRO comparison.
Capture ePRO
The participant questionnaire product.
Free sandbox with every feature. No credit card, and you pay only when you go live with real participants.