IVDR Companion Diagnostics: The Consultation Gate Before Your CE Certificate

Regulation (EU) 2017/746 (IVDR), in full application since May 26, 2022, classifies most companion diagnostics as Class C under Annex VIII, Rule 3(a). That fact tells you which notified body reviews your device. It does not tell you the whole story. Article 48(3) adds a second, mandatory step most device and IVD teams underweight when they build their submission timeline: before the notified body can issue a certificate, it must obtain a scientific opinion from a medicines regulator on whether the diagnostic is suitable for use with the specific medicinal product it's paired to.

Classification sets the review path, not the whole path

IVDR defines a companion diagnostic as a device essential for the safe and effective use of a corresponding medicinal product — identifying, before or during treatment, patients most likely to benefit, or patients at increased risk of a serious adverse reaction. Annex VIII, Rule 3(a) puts most of these devices in Class C, requiring notified body involvement in the conformity assessment. The exception is narrow: a companion diagnostic used to determine suitability for a blood-derived product, an immunosuppressant, or a cell or gene therapy product moves up to Class D, which carries its own additional requirements. Getting the classification right is a necessary first step for any in vitro diagnostic strategy — but it is the easy part of this particular submission.

What the consultation actually requires

The notified body cannot resolve the medicinal-product question on its own technical expertise, and IVDR doesn't ask it to. Article 48(3) routes the question to whichever regulator actually authorized the corresponding medicine: the EMA when that medicinal product went through the centralized procedure, or the competent authority of the relevant Member State when it was authorized nationally. The notified body submits the CDx's performance evaluation data and receives a scientific opinion on suitability in return. If the notified body's own conclusion diverges from that opinion, it has to justify the divergence in writing rather than simply proceed — which in practice means the opinion carries real weight in whether and how the certificate gets issued. This sits alongside, but is distinct from, the broader EU MDR & IVDR compliance obligations a device manufacturer is already managing.

• Two authorities, two clocks. The notified body's technical review and the medicines regulator's consultation run on separate timelines that both have to clear before certification.
• The product-specific claim is what's being tested. The consultation isn't evaluating your assay in isolation — it's evaluating suitability for a specific medicinal product and indication.
• Sponsor coordination isn't optional. The pharma sponsor's own regulatory procedure for the medicinal product and the IVD manufacturer's CDx submission are functionally linked, even though they're formally separate applications.
• Class D triggers additional requirements. The narrow Class D carve-out for CGT- and biologic-paired diagnostics adds EU reference laboratory involvement on top of the consultation — a different, further mechanic covered separately.

Classification tells you which notified body reviews your device. It says nothing about which medicines regulator has to agree with them first. The mechanic Article 48(3) actually adds

Building the timeline around someone else's clock

The practical failure mode is treating the notified body's review as the pacing item and the consultation as a formality layered on top. It runs the other way: the consultation's statutory window is the harder constraint to compress, because it depends on a regulator outside your notified body relationship, and its outcome can require you to revisit the performance data before certification proceeds. The scientific validity and clinical performance evidence the consultation reviews needs to be built to withstand a second regulator's scrutiny, not just the notified body's, from the start — not assembled to satisfy one reviewer and then patched for the other.

None of this changes the underlying classification work or the performance evaluation science — it changes when you start planning for a step that isn't the notified body's to control. Manufacturers who treat the Article 48(3) consultation as a late-stage formality are the ones who discover, months into review, that a second regulator's clock was running the whole time. Our companion diagnostics regulatory strategy work exists to build that sequencing in from the first submission plan, not after a delay surfaces it.