The IVDR in Plain Language: How Europe Regulates Diagnostic Tests

The EU In Vitro Diagnostic Regulation (IVDR, Regulation (EU) 2017/746) is the law that governs how diagnostic tests reach the European market, from a home pregnancy kit to the genetic assay that decides whether a cancer drug is prescribed. Its central move is a risk-based system that sorts tests into four classes and, for most of them, requires an independent body to check the evidence before a CE mark can be applied. That is a sharp departure from the old directive it replaced, under which the great majority of tests were essentially self-declared by their makers. This article explains the framework in plain language as public policy, not legal advice; for decisions about a specific product or a specific diagnosis, talk to a qualified professional or your own clinician.

What counts as an in vitro diagnostic

An in vitro diagnostic, or IVD, is a test performed on a sample taken from the body rather than on the body itself. Blood glucose meters, HIV antibody tests, PCR assays for infectious disease, tumor-marker panels, and the software that interprets any of these all fall inside the definition. The common thread is that the result informs a medical decision: whether a person has a condition, how severe it is, whether a treatment is likely to work, or how a therapy should be dosed. Because those decisions ripple outward, a wrong result can harm the person tested and, in the case of a transmissible infection, the people around them. The regulation is built around that reach.

From a directive to a regulation

Before 2022, in vitro diagnostics in Europe were governed by the In Vitro Diagnostic Directive (98/79/EC). Under that older regime, only a short list of higher-concern tests, such as those screening blood donations, required review by an outside organization. Everything else, by most estimates the large majority of tests on the market, could be placed on sale on the manufacturer's own declaration of conformity. The IVDR inverts that default. Where the directive left roughly eight to twenty percent of tests subject to independent oversight, the regulation is generally understood to push that figure toward eighty percent or more. This was not only a matter of stricter rules at the top. The whole population of tests was re-sorted, and a product that once needed no external review may now need a full one.

The four risk classes

The IVDR places every test into one of four classes, defined by classification rules in the regulation's annexes. The logic combines two things: the danger posed by an incorrect result to the individual, and the danger posed to public health.

• Class A is the lowest risk, covering items such as general laboratory instruments and specimen receptacles.
• Class B covers many general-purpose tests that do not carry the higher stakes of the classes above it.
• Class C covers tests where an error carries serious consequences for the patient or for management of a condition, including many cancer, genetic, and infectious-disease assays.
• Class D is the highest risk, reserved for tests where an error threatens public health, such as those detecting a transmissible agent in blood or organs intended for transfusion or transplant.

Only Class A tests that are not sold sterile can reach the market on the manufacturer's declaration alone. For Classes B, C, and D, an independent organization has to be involved.

The bigger role of notified bodies

That independent organization is called a notified body: a private entity designated and audited by an EU member state to assess whether a product meets the regulation. It is not a government agency, and it does not follow the American model either. A notified body's CE mark says a product satisfies the applicable European rules; it is a different mechanism from clearance or approval by the U.S. Food and Drug Administration, which reviews devices directly. Both aim at safety and performance, and the institutional path differs.

Under the IVDR, notified bodies examine a manufacturer's technical documentation, quality system, and clinical evidence, and for the highest-risk tests the scrutiny is deepest. Because so many more products now fall into the classes that require this review, the demand for notified-body capacity has been a defining feature of the transition, and a limited number of designated bodies is one reason the timelines have been extended more than once.

What the evidence has to show

The most consequential change is what a manufacturer now has to demonstrate. The IVDR asks for a structured demonstration of clinical evidence built on three pillars: scientific validity, meaning the analyte the test measures is genuinely associated with the condition; analytical performance, meaning the test accurately detects what it claims to detect; and clinical performance, meaning the result corresponds to the clinical state it is used to identify. This evidence is not a one-time exercise. Manufacturers must run post-market performance follow-up and vigilance, monitoring how a test behaves in real use and reporting serious incidents. Much of this is registered in EUDAMED, a European database intended to make devices, certificates, and safety signals more traceable across the single market.

Why companion diagnostics matter here

A companion diagnostic is a test that determines whether a particular patient should receive a particular medicine, for example an assay for a tumor mutation that a targeted therapy is designed to act on. Under the IVDR these tests generally sit in Class C, and their assessment can pull in more than a notified body: the regulation provides for consultation with the European Medicines Agency or a national competent authority, linking the test to the medicine it guides. That linkage is the point. When a drug's benefit depends on selecting the right patients, the quality of the test is inseparable from the safety of the treatment, and the framework treats them as a pair rather than as two unrelated products.

Why it matters for labs and patients

For laboratories, the practical effect is that tests developed and used in-house now face defined conditions and, in some situations, obligations that once applied only to commercial products. For patients, the intended payoff is a market where a test's claims rest on assessed evidence rather than self-assertion, with a traceable trail if something goes wrong. The trade-off is real: more evidence and more oversight raise cost and can slow how quickly a niche test reaches the people who need it, which is part of why the phased deadlines run into the late 2020s. Reasonable people weigh those costs and benefits differently, and that debate is a healthy part of how a framework like this matures.