Performance studies under Regulation (EU) 2017/746 (IVDR) rarely run exactly as first approved. Sites change, sample sizes are revised, a procedure is added. Most changes only need to be documented. Some must be notified to the Member State before they are made, and the IVDR is precise about which ones and how long you wait.
What counts as substantial
A modification is substantial when it is likely to have a substantial impact on the safety, health or rights of the subjects, or on the robustness or reliability of the data the study generates (IVDR Article 71(1)). The test is about likely impact, not about the size of the change on paper. A small wording change to the inclusion criteria can be substantial; a change of courier usually is not. When in doubt, write down the reasoning either way, because an inspector will ask for it.
The procedure
The sponsor notifies the Member State or States where the study is running within one week, giving the reasons for and nature of the change, with updated versions of the affected Annex XIV documents and the changes clearly identifiable. The Member State assesses the modification under the same procedure it uses for applications.
The sponsor may implement the change 38 days after the notification at the earliest, unless the Member State has refused it, or an ethics committee in that Member State has given a negative opinion valid for the whole country. The Member State may extend the 38 days by a further seven days to consult experts.
Build that into the study plan. A change you know you will need in month four should be notified in month two.
How to notify while EUDAMED is incomplete
The IVDR expects the notification to go through EUDAMED’s module for clinical investigations and performance studies. That module is not among the four EUDAMED modules that became mandatory on 28 May 2026, so the national route still applies. In practice that means the documents the Medical Device Coordination Group published for the interim: MDCG 2022-19 (December 2022) for applications and notifications, and MDCG 2022-20 (December 2022), a template for notifying a substantial modification. MDCG 2022-20 was meant to be withdrawn once the EUDAMED module is fully functional; that has not happened, and the Commission’s guidance page still lists it. Check with the national competent authority (INFARMED in Portugal) whether it also asks for a national form.
When the module is declared functional, a six-month transition will follow before its use is mandatory. Plan for one more switch of format during a long study.
What it means for your product
Keep a change log for every performance study, with a short assessment of each change against the Article 71 test. Agree with the investigators who can propose changes and how fast you will hear about them, because the one-week clock runs from your decision, not theirs. And use the MDCG 2022-20 template now: it is what competent authorities expect to receive.
IVD performance evaluation is part of our evidence work under the IVDR: Evidence and technical documentation.
Related briefing: What is EUDAMED? Modules, actor registration and the 27 November 2026 deadline