Class B is IVDR's default, not its safest guess

A classification file for a new assay often starts the way a medical device classification tool does under 21 CFR 860.3: pick the risk band, check the exceptions, move on. IVDR Annex VIII runs the same-sounding exercise on a different structure, and the difference changes the default outcome. Regulation (EU) 2017/746 sorts every in vitro diagnostic into Class A, B, C, or D by working down from the highest-risk rule, and the rule most devices actually land on — the residual rule that catches whatever the named ones didn't — doesn't default to the lightest oversight the old directive left in its silence. It defaults to Class B, and Class B already means a notified body is in the file.

Seven rules, applied by exclusion, and the higher answer always wins

Annex VIII sets out seven classification rules, and its implementing rules govern how they interact rather than leaving each rule to stand alone. Where a manufacturer states more than one intended purpose for a device and those purposes fall into different classes, the device takes the higher class. Where more than one rule could plausibly apply to the same device, the rule that produces the higher classification is the one that governs. Software gets no separate track: software that drives or influences the use of a device takes that device's class, and only software with no other device behind it is classified in its own right. None of this is optional sequencing — a file that picks the rule giving the lower class because it also happens to fit has applied the annex backwards.

Class D is reserved for a short, named list

Rule 1 sets the top of the scale narrowly: devices used to detect a transmissible agent in blood, tissue, cells, or organs to assess donor suitability, devices used to detect a life-threatening, highly transmissible disease, or devices used to determine infectious load where that result is critical to patient management — HIV, hepatitis B and C, and comparable agents are the standing examples. Class D isn't a general “high-risk infectious disease” bucket; it's this specific combination of donor safety and public-health consequence, and a test that misses blood-transmissible disease but serves a different diagnostic purpose belongs further down the scale even when the underlying pathogen sounds equally serious.

Self-testing moves the class up, except where four exceptions move it back down

Rule 4 raises the class for devices intended for self-testing by a lay user, defaulting them to Class C rather than whatever class the same test would carry in a professional laboratory — except for pregnancy tests, fertility tests, cholesterol tests, and urine tests for glucose, erythrocytes, leukocytes, or bacteria, which the rule pulls back down to Class B. A near-patient device used by a trained professional outside a lab setting doesn't get the same upward push; it's classified the way the test would be classified in a lab in the first place.

The residual rule is where the real shift from the old directive lands

General laboratory instruments and reagents with no specific diagnostic purpose of their own sit at the bottom, in Class A. Everything Rules 1 through 5 don't name falls to Rule 6, the residual rule — and Rule 6's default is Class B, not self-declaration. Under the IVD Directive this replaced, most devices in that same residual position were self-certified with no notified body involved at all. Under IVDR, landing in the residual rule still means a notified body reviews the file; the annex's default moved, even where the underlying test itself didn't change.

Even Class A isn't fully outside notified-body reach

Class A looks like the one clean exit from notified-body review, and for a non-sterile device it is — a manufacturer can self-certify against Annex I's general safety and performance requirements without a notified body reading the file at all. A device placed on the market sterile breaks that exemption in one specific place: a notified body still has to assess the manufacturing steps that establish, secure, and maintain sterility, even though every other aspect of the device stays self-certified. A classification file that records “Class A” and stops has skipped the one follow-up question that actually decides whether a notified body's name ever appears on this device's paperwork.

Where this meets the rest of the file

The class a device lands on here isn't the end of the file — it sets how deep the performance evaluation's three legs have to go and how often its PMPF plan has to report back. A classification worksheet built around Annex VIII's actual exclusion order — rather than a single risk-band guess — is previewed in the launch catalog. If your program classifies an IVD differently, the shelf takes that correction directly.