Substantial equivalence
Substantial equivalence is the legal standard a 510(k) must meet. A device is substantially equivalent when it has the same intended use as a predicate device, and either the same technological characteristics, or different characteristics that do not raise different questions of safety and effectiveness. A clearance is not a finding that a device is safe and effective in the abstract. It is a finding that the device is as safe and as effective as one already on the market.
FD&C Act 513(i); 21 CFR 807.100(b); FDA 510(k) Program guidance, July 2014
At a glance
| The test | Same intended use, AND either same technological characteristics, or different ones that do not raise different questions of safety and effectiveness. |
|---|---|
| "Different technological characteristics" | A significant change in the materials, design, energy source or other features, compared with the predicate. |
| Where it is written | FD&C Act 513(i)(1)(A). Mirrored at 21 CFR 807.100(b). |
| How FDA decides | A published six-point decision flowchart. A wrong answer at points 1, 2 or 4 ends the route. |
| What determines intended use | The proposed labeling submitted in the 510(k). Stated in FD&C Act 513(i)(1)(E)(i). |
| Least burdensome | FDA is required to request only information necessary to make the determination. |
| If found not equivalent | Four options: resubmit with new data, request De Novo, file a reclassification petition, or submit a PMA. |
| Rate of intended-use failures | FDA states roughly 10 percent of all NSE decisions are due to a new intended use. |
How FDA works through it
FDA publishes the decision sequence it applies. Six points, each with the regulation behind it.
| Point | The question FDA asks | Fails to |
|---|---|---|
| 1 | Is the predicate device legally marketed? | Not substantially equivalent |
| 2 | Do the devices have the same intended use? | Not substantially equivalent |
| 3 | Do the devices have the same technological characteristics? | Point 4, not to failure |
| 4 | Do the different technological characteristics raise different questions of safety and effectiveness? | Not substantially equivalent, if yes |
| 5a | Are the methods used to evaluate them acceptable? | Not substantially equivalent |
| 5b | Do the data demonstrate substantial equivalence? | Not substantially equivalent |
Point 3 is the one most often misread. Answering "no" does not end the submission. Different technological characteristics are permitted, and the submission moves to point 4, where the question becomes whether those differences raise new questions rather than whether they exist.
Two terms that are not interchangeable
Intended use is the general purpose of the device or its function. Indications for use describe the disease or condition the device will diagnose, treat, prevent, cure or mitigate, including the patient population it is intended for.
Intended use encompasses indications for use. This is the operative relationship: a finding of substantial equivalence means the indications for use of the new device fall within the intended use of the predicate, and therefore the two devices have the same intended use.
FDA determines intended use from the proposed labeling in the submission. Not from what the manufacturer says it means, and not from the device's technical capability.
Where a device has general indications that do not name a disease, condition or population, FDA treats intended use and indications for use as the same thing. FDA calls these "tool type" indications.
After a Not Substantially Equivalent decision
FDA states four options. Which of them is genuinely open depends on why the decision was reached.
- Resubmit another 510(k) with new data.
- Request Class I or II designation through the De Novo process.
- File a reclassification petition.
- Submit a premarket approval application.
FDA treats NSE decisions as falling into two categories. The first is an affirmative determination that the device is Class III and cannot be reviewed in a 510(k) — no predicate, a new intended use, or different characteristics raising different questions. The device is then automatically Class III and requires a PMA, or a De Novo if eligible.
The second is a finding that the evidence submitted was insufficient. FDA states that NSE decisions based on a lack of performance data do not preclude a new 510(k) containing different or additional data.
A new 510(k) after an NSE requires a new user fee. FDA is explicit about this: the submission is treated as new, and the fee in effect at the time applies.
Questions people ask
Does substantial equivalence mean identical?
No. Devices may differ in materials, design and energy source. The question is whether those differences raise different questions of safety and effectiveness, not whether they exist.
Does a clearance mean FDA approved our device?
No. FDA cleared it. Clearance means FDA found the device substantially equivalent to a legally marketed predicate. Approval is the term for a PMA. The words are not interchangeable and using the wrong one in labeling or promotion has consequences.
Can FDA require clinical data in a 510(k)?
Yes, where FDA deems it necessary to demonstrate the device is as safe and effective as the predicate. FDA is required by statute to consider the least burdensome means and to request only information necessary to make the determination.
What if our device is better than the predicate?
Being better does not by itself help. A significant improvement can constitute a different technological characteristic, which moves the submission to decision point 4 and may require performance data to show the difference raises no new questions.
Can we go straight to De Novo without a 510(k) first?
Yes. Since FDASIA in 2012, a De Novo request may be submitted directly where the requester has determined there is no legally marketed device on which to base a determination of substantial equivalence.