What a 510(k) actually is — and what clearance means

A 510(k) is not an application for approval, and the FDA does not approve what you submit. Under 21 CFR 807 subpart E it is a premarket notification: a demonstration that your device is substantially equivalent to one already legally on the market. The reviewer is not judging your device on its merits. They are judging a comparison — which means the most consequential decision in the file was made before a single test was run: the choice of predicate.

Why the framing matters

If you believe a 510(k) is an approval, you write it to showcase the device. You lead with performance, you broaden the indications, you treat the predicate as a formality. Every one of those instincts damages the file. The reviewer's question is comparative — is this as safe and effective as the predicate? — so material that does not serve the comparison is noise, and claims that outrun the predicate's intended use are not ambition. They are a different regulatory question, and often a different pathway.

This is why the same team that plans an IND around a clock that runs out has to relearn everything for devices. The two pathways teach opposite lessons about silence: an IND goes into effect because 30 days passed. A 510(k) confers nothing until the agency acts. Sponsors who carry the drug lesson into a device programme plan launches against a date the regulation never promised them.

The terms, precisely

Predicate device

The legally marketed device the comparison is made against — on the market before the 1976 Medical Device Amendments, or itself cleared through the 510(k) process. A device removed from the market at the agency's initiative cannot serve as a predicate.

Substantial equivalence

The finding, under section 513(i) of the FD&C Act, that the device has the same intended use as the predicate and either the same technological characteristics, or different ones that raise no different questions of safety and effectiveness and are shown to be as safe and effective as the predicate.

Intended use

What the device is for, as the labeling states it. Indications for use narrow it further. Broaden either past what the predicate supports and you are no longer making the same comparison — you are asking a question your file was not built to answer.

Not substantially equivalent (NSE)

The finding that ends the pathway. An NSE device is Class III by operation of law and requires an approved PMA to market — unless it qualifies for De Novo classification as a novel device of low to moderate risk.

What the file actually argues

Notice what is missing: an absolute demonstration that the device is safe and effective. That is the PMA's question, answered with clinical evidence and answered independently. Sponsors who write a 510(k) as if it were a small PMA bury the comparison the reviewer is paid to find. Sponsors who treat the comparison casually discover that similar is not a regulatory standard — substantial equivalence is a defined term, and the definition is where 510(k)s live or die.

The 90 days, honestly

FDA aims to reach a decision on a 510(k) within 90 FDA days under its MDUFA performance goals. A goal is not a guarantee, and it is not a clock that confers anything: nothing happens by default at day 90, and no amount of silence puts a device on the market. The file first survives an acceptance review, then a substantive one — and an additional-information request stops the review entirely, with 180 days to respond completely before the submission is considered withdrawn.

So the honest project plan has no “FDA approval” milestone and no launch date pinned to day 90. It has a submission date, an acceptance decision, one planned pause for additional information — because most first submissions get one — and a decision letter: SE, or NSE with a serious conversation about De Novo. Teams that plan against the goal have planned against a number someone else set for a file they had not yet seen.

Where 510(k)s go wrong

Choosing the predicate by convenience

The easiest predicate to find is rarely the closest to your device. Every technological difference you cannot dismiss becomes a testing obligation, and a predicate with broader claims than yours helps nobody — the comparison runs on your intended use, not theirs. Choose the predicate the way the reviewer will read it: as the definition of the question.

Writing indications the predicate cannot support

Marketing wants the broader claim; the comparison needs the same intended use. An indication that outruns the predicate raises exactly the different questions of safety and effectiveness that end substantial equivalence. The expansion belongs in a later submission, after clearance — not smuggled into this one.

Treating clearance as the finish line

Clearance is permission to market the device described in the file. Change it — materials, software, sterilisation, intended use — and 21 CFR 807.81(a)(3) asks whether the change could significantly affect safety or effectiveness. If it could, that is a new 510(k). The comparison you cleared is the device you must keep making.

Frequently asked questions

Is a cleared device “FDA-approved”?

No, and the agency polices the distinction. Approval follows a PMA's independent demonstration of safety and effectiveness; clearance is a finding that the device is substantially equivalent to a legally marketed predicate. Marketing a cleared device as “approved” misbrands it.

What happens if FDA finds a device not substantially equivalent?

An NSE determination places the device in Class III by operation of law, and marketing it requires an approved PMA — unless it qualifies for De Novo classification as a novel device of low to moderate risk. A device granted De Novo can then serve as a predicate for future 510(k)s.

Does every change to a cleared device need a new 510(k)?

No. A new submission is required when a change could significantly affect the device's safety or effectiveness, or is a major change in intended use, under 21 CFR 807.81(a)(3). Other changes are assessed and documented to file, with the rationale FDA expects to see at inspection.