What is a predicate device, and how do I choose one?

In short: A predicate is a legally marketed device your 510(k) claims substantial equivalence to — same intended use, comparable technological characteristics. Choose by matching intended use first, technology second, and checking the predicate's own history. Predicate mismatch is the most common cause of substantial-equivalence problems — the Additional Information requests and holds that stall 510(k)s.

What "substantial equivalence" actually requires

A predicate device is a device already legally on the US market — cleared via 510(k), granted through De Novo (which creates a new classification others can cite), reclassified, or on the market before FDA's current regulatory framework applied — that your device claims to be substantially equivalent to. Substantial equivalence has two components: the same intended use, and either the same technological characteristics or, where they differ, evidence the differences don't raise new questions of safety or effectiveness. Intended use is the harder, more decisive test — a technically similar device with a subtly different intended use is not a usable predicate, no matter how close the underlying technology looks.

How to actually search

Start with FDA's own 510(k) database, searching by product code and intended use language close to your own, not just by company or product name. Read the predicate's own 510(k) summary closely — its stated intended use, its technological characteristics, and critically, what predicate it claimed equivalence to. A predicate that itself relied on a weak or contested equivalence argument — or one that has since been recalled or drawn safety signals — is a riskier foundation for your own submission than one with a clean, well-documented lineage. And plan around a single predicate: stitching together features from multiple predicates (the "split predicate" anti-pattern) invites a not-substantially-equivalent finding.

Why mismatch is the most common source of trouble

Founders often reach for the most well-known or successful product in their space as a predicate, without checking closely enough whether its actual FDA-cleared intended use matches their own product's real function. A predicate cleared for "monitoring" when your device performs "diagnosis," or one cleared for a narrower patient population than yours, creates exactly the kind of equivalence gap that generates an Additional Information request or an outright rejection. Getting predicate selection right before submission — including running it past someone who's evaluated 510(k) submissions before — is cheaper than discovering the mismatch mid-review.

Where next: 510(k) vs De Novo vs PMA: Which FDA Pathway · Which FDA pathway applies: 510(k), De Novo, or PMA?

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