When Beating the Predicate Breaks Your 510(k)

A regulatory professional posted a question on a forum that hard-tech founders get backwards all the time. Their device puts out a higher voltage than the predicate it wants to clear against. Same intended use, similar build everywhere else. Would the FDA still call it substantially equivalent? The instinct behind the question is that a stronger spec helps the case. Under the way a 510(k) actually gets read, the number that beats the predicate is often the number that knocks you out of the lane.

What substantial equivalence actually tests

A 510(k) clears your device by showing it is substantially equivalent to one already on the market. The law that governs the program, section 513 of the Food, Drug, and Cosmetic Act, sets the bar in two parts. Same intended use, and either the same technological characteristics or different ones that do not raise different questions of safety and effectiveness. The phrase doing the work is “different questions.” The test is not whether your device is as good as the predicate or better. It is whether the difference introduces a safety or effectiveness question the predicate’s data never had to answer.

Higher output voltage is a change in how the device delivers energy, and energy source is one of the features the statute names. So the question a reviewer asks is not whether more voltage is better. It is whether more voltage creates a risk, such as thermal injury or unintended stimulation, that the cleared predicate was never evaluated against. If it does, you owe performance data to close that question, and the data may have to be clinical.

Where the airtight predicate argument falls apart

I have watched a predicate argument that looked airtight collapse on exactly this seam. At Galen we built a cooperative-control robot for skull-base surgery, and we were sure it was a slam-dunk 510(k) against the da Vinci. The case was stronger than category overlap. We shared software lineage with da Vinci, and Russ Taylor had written the original code. From where we sat, the predicate logic was clean.

The FDA did not see it our way. They told us the indication did not match, that ours was a different kind of system, and that it would be advisable to consider another path. They never ordered the De Novo. In agency language, “advisable to consider” is the answer, so we took the hint. The lesson sits right under the voltage question. Predicate logic that looks binding to you is not binding on the FDA. What ends a 510(k) is not a worse device. It is a difference the agency decides raises a new question, and your shared code or your stronger number does not settle that for them.

The two honest roads, decided early

Here is the choice when your differentiator is the difference that breaks equivalence. You have two honest roads, and the work is picking between them before you write a line of the submission. Keep the 510(k) and generate the data that closes the new question, paying the time and cost to do it. Or stop forcing the predicate and run a De Novo. The same law that defines equivalence lets a device with no fair predicate, or one found not substantially equivalent, ask the FDA to classify it as low or moderate risk on its own terms.

Founders hear De Novo as a demotion. It is closer to the opposite. You write the safety story the agency adopts, and when it is done you become the predicate that everyone after you has to clear against. This applies to any hard-tech founder whose pitch leans on a number that beats what is already cleared. Higher power, faster cycle, finer resolution. The improvement you sell to investors is the same improvement a reviewer reads as a new question. The earlier you decide which road that number puts you on, the cheaper the whole file gets.

Dave Saunders is the founder of Base Reality Group and a Fractional CPO for hard-tech founders. He was a founder and operator at Galen Robotics, where the surgical-robotics platform earned FDA De Novo authorization in 2023, and he managed a 35-patent portfolio licensed from Johns Hopkins. He wrote Founders Who Finish and publishes The Build. More about Dave →