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Imported item 10
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Term of the Day

Natural history study

A natural history study is a preplanned observational study intended to track the course of a disease over time, identifying demographic, genetic, environmental and other variables that correlate with its development and outcomes in the absence of intervention, or under standard of care. Designs may be retrospective (chart review of existing records) or prospective (longitudinal follow-up of a cohort or registry).

Natural history data is particularly important in rare and paediatric diseases, where randomised placebo-controlled trials may be infeasible or unethical. The FDA (guidance on rare disease natural history studies, 2019) and the EMA accept well-designed natural history studies to define endpoints and biomarkers, identify patient subgroups, estimate sample sizes and, in some cases, serve as external or historical control arms for single-arm trials supporting orphan products.

Because they are non-interventional, natural history studies fall outside the CTR and are governed by national law (for example France's MR-003 or MR-004 reference methodologies) and by the GDPR. They typically involve secondary use of medical records, long-term follow-up, genetic data and small populations in which anonymisation is rarely achievable, so pseudonymisation, a DPIA and a robust research legal basis under Art. 9(2)(j) are essential. Registries maintained by patient organisations or academic consortia raise additional questions of joint controllership and data access governance.

E

Imported item 44

An electronic patient-reported outcome, or ePRO, is information about a patient’s health reported directly by that patient using an electronic collection method. The electronic format changes how the response is captured, not who supplies it. In clinical studies, an ePRO might be collected through a diary app, website or dedicated device.

Key takeaways

  • The patient remains the source of the report.
  • ePRO is one type of electronic outcome assessment.
  • Assess the collection platform and its data flows.

ePRO, PRO and eCOA Compared

The FDA guidance on fit-for-purpose clinical outcome assessments explains that changing to an electronic mode does not change the source of a clinical outcome assessment. A sensor measurement is not automatically a patient-reported response.

TermDistinction
PROA report directly from the patient, without another person’s interpretation.
ePROA PRO captured electronically.
eCOAThe broader electronic collection of clinical outcome assessments.

Why It Matters for Data Protection

For an ePRO deployment, we recommend mapping the response data separately from account details, device information and support logs. Ask who can link a study code to a person, where each dataset is hosted and which suppliers can access it. Include notification content, shared devices and account recovery in the review; a discreet questionnaire can still expose participation through an avoidable message.

Hypothetical example: A participant completes a daily symptom diary at home. The study team configures neutral reminders, restricts identifiable support records and tests export access before enrolment. It also checks how missed entries and later corrections will be recorded, rather than treating app installation as the end of implementation.

Frequently Asked Questions

Is every health app an ePRO tool?

No. The relevant feature is direct electronic patient reporting, not simply being a health app.

Can someone help a participant use the device?

Assistance need not change the assessment type if the helper does not interpret the patient’s response.

Does electronic collection guarantee suitability?

No. Assess the instrument, population, context and implementation for the intended use.

Related reading: patient-reported outcomes, electronic clinical outcome assessments. For practical support, see vendor assessment.

Updated: 27 October 2026