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E
Explicit consent
F
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F
FDPIC (Swiss Federal Data Protection and Information Commissioner)
F
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F
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F
Food and Drug Administration (FDA)
F
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G
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Health data access body (HDAB)
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Joint controllers
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Natural history study
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Q
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Q
Quality management system (QMS)
Q
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Query (clinical data query)
R
Randomisation and trial supply management (RTSM)
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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.

C

Companion diagnostic

A companion diagnostic is a test that provides information essential to using a particular medicine safely and effectively. It can help identify patients likely to benefit or face particular treatment risks. The relationship to the medicine is central: not every biomarker test is a companion diagnostic.

Key Takeaways

  • A companion diagnostic supports a treatment decision linked to a specific medicinal product.
  • FDA and EU frameworks both connect the diagnostic’s performance to the safe and effective use of the medicine.
  • Biomarker workflows need clear responsibilities for samples, test results and any linked patient information.

How Does a Companion Diagnostic Differ?

ElementMeaning
Diagnostic testProvides information about a condition
Companion diagnosticEssential to use of a corresponding medicine
Exploratory biomarkerInvestigated without necessarily establishing clinical use

The FDA describes companion diagnostics as medical devices, often in vitro diagnostics, that can guide selection or treatment monitoring. In the EU, the IVDR provides a specific framework, including notified-body conformity assessment and consultation with a medicines authority where applicable. EMA’s role is to assess the suitability of the diagnostic for the medicinal product in the consultation procedure; this should not be confused with the entire device assessment.

Primary guidance: FDA companion diagnostics; EMA companion diagnostics.

Why It Matters for Data Protection

Consider a hypothetical oncology study using a tumour mutation to determine eligibility. We recommend mapping the path from the hospital sample to the testing laboratory, study database and sponsor. Record which organisation receives the full laboratory report and which needs only an eligibility result. Separate the clinical testing purpose from optional future research. Explain relevant uses to participants, and check retention and access arrangements for both the specimen and the derived data. Avoid assuming that a coded sample or result is anonymous merely because the sponsor does not receive a name.

Frequently Asked Questions

Are all genetic tests companion diagnostics?

No. The intended relationship with a medicine determines the distinction.

Is every companion diagnostic genetic?

No. The definition is not limited to genetic biomarkers.

Does a test replace clinical judgement?

No. It supplies information for the medicine’s defined use and treatment decision.

Related reading: in vitro diagnostic regulation ivdr; genetic data.

Explore iliomad’s healthtech medtech AI diagnostics support for your organisation.

Updated: 27 October 2026