Who does the notified body consult, and how long does it take?

Under Article 48(5) the notified body seeks a scientific opinion from the EMA when the associated medicinal product is centrally authorised, or from the competent authority that authorised the product otherwise. The consulted body has 60 days to respond, extendable once by a further 60 days, so plan for several months of added assessment time on top of the normal Class C route.

Can one companion diagnostic cover several medicinal products?

Yes, provided the intended purpose names each product and the performance evidence supports every claimed drug-biomarker pairing. Each pairing needs its own clinical performance data, and the consultation covers the full set, so adding a product later is a change that triggers reassessment.

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RegulatoryRegulated Pathways Global Markets Startup LifecycleCDx

Companion Diagnostic (IVDR)

IVD that is essential for the safe and effective use of a corresponding medicinal product to identify eligible patients or monitor treatment response.

Reviewed by Christian Espinosa, Founder, Blue Goat CyberLast reviewed July 25, 2026

Definition

Article 2(7) of the IVDR defines a companion diagnostic as a device essential for the safe and effective use of a corresponding medicinal product to (a) identify, before or during treatment, patients most likely to benefit, or (b) identify patients likely to be at increased risk of serious adverse reactions. Rule 3(c) of Annex VIII classifies companion diagnostics as Class C.

What the regulation says

Article 48(5) and Annex IX Section 5.2 require notified bodies to seek a scientific opinion from the EMA or a national competent authority when assessing companion diagnostics linked to a centrally or nationally authorised medicinal product.

What this means in practice

CDx conformity assessment requires a mandatory consultation between the notified body and the EMA (or a Member State competent authority) on the suitability of the device in relation to the medicinal product. This adds meaningful lead time versus a non-CDx Class C IVD and requires the manufacturer to align its evidence package with the drug label.

Examples

A companion diagnostic test identifies specific gene mutations in cancer patients to determine their eligibility for a targeted chemotherapy drug, maximizing the drug's efficacy and minimizing ineffective treatment.
Before prescribing a new biologic for an autoimmune disease, a CDx is used to detect a particular biomarker in a patient's blood, ensuring the patient is likely to respond positively to the therapy.
A companion diagnostic assay screens for genetic predispositions that could lead to severe adverse reactions to a particular psychiatric medication, allowing clinicians to select a safer alternative for at-risk individuals.

Common pitfalls

•Assuming a biomarker assay is a CDx only if the drug label names it. IVDR looks at the intended purpose claimed by the IVD manufacturer.
•Underestimating the EMA consultation timeline in project plans.
•Failing to coordinate label changes between pharma partner and IVD manufacturer, which can invalidate the CDx claim.

Frequently asked questions

No. Only tests essential for the safe and effective use of a specific medicinal product meet the Article 2(7) definition. Complementary diagnostics that inform but are not required for use are not CDx.

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Clinical Performance (IVDR)

The ability of an IVD to yield results correlated with a clinical condition in the target population and intended user.

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EU In Vitro Diagnostic Regulation(IVDR)

Regulation (EU) 2017/746 governing in vitro diagnostic medical devices in the EU.

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IVDR Risk Classes A–D

EU IVDR's risk-based classification: Class A (lowest) to Class D (highest).

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Scientific Validity (IVDR)

The association of an analyte with a clinical condition or physiological state.

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Category: Regulatory
Acronym: CDx
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Updated: 7/25/2026

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Learn in 60 seconds

IVD that is essential for the safe and effective use of a corresponding medicinal product to identify eligible patients or monitor treatment response.

·This adds meaningful lead time versus a non-CDx Class C IVD and requires the manufacturer to align its evidence package with the drug label.
·Rule 3(c) of Annex VIII classifies companion diagnostics as Class C.

Remember this

Watch out: Assuming a biomarker assay is a CDx only if the drug label names it. IVDR looks at the intended purpose claimed by the IVD manufacturer.

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