CDRH's Premarket Notification process runs on one central argument: the subject device is substantially equivalent to a legally marketed predicate. That argument only holds up if every claimed similarity traces back to a cited source, not an assumption carried over from a prior submission.
What "substantially equivalent" actually requires
A 510(k) submission doesn't ask whether the new device is good. It asks whether it's equivalent, in indications for use and in technological characteristics, to a device CDRH has already cleared. That comparison has to be built side-by-side, feature by feature, with FDA guidance cited directly rather than paraphrased from memory.
- Comparing the subject device against the predicate's cleared indications for use
- Comparing technological characteristics side-by-side, not summarizing them
- Citing FDA guidance directly to support each claimed equivalence
- Organizing risk analysis, performance testing, and labeling into the applicable exhibits
Where these submissions get flagged
An FDA Refuse-to-Accept or Additional Information request rarely comes from a device that's genuinely different from its predicate. It comes from an incomplete comparison or a missing required exhibit, gaps that a careful side-by-side review would have caught before submission, not after.
The comparison is the submission
Completing the substantial equivalence comparison and its supporting summary documents wasn't a formality attached to the 510(k), it was the core of it. Every other exhibit, risk analysis, performance data, labeling, exists to support that one central claim.
The Real Takeaway
A substantial equivalence argument is only as strong as its side-by-side comparison to the predicate.
Every claimed similarity needs a cited source, not an assumption, or it becomes the exact gap an Additional Information request is designed to find.