Discover how FDA device classes (I–III) define regulatory paths: 510(k) clearance for moderate risk, De Novo for novel low-to-moderate risk, and PMA approval for high-risk devices. Learn when PMA is required and how to choose the right path.
Medical device regulatory pathways depend primarily on the device’s classification and level of risk. The FDA broadly classifies devices into Class I (low risk), Class II (moderate risk), and Class III (high risk). Each class has an associated premarket pathway: Most Class I devices are exempt from premarket review; most Class II devices require a 510(k) premarket notification (demonstrating substantial equivalence to a predicate device); and Class III devices generally require a Premarket Approval (PMA). A De Novo classification request is a route to down-classify novel low-to-moderate risk devices into Class I or II when no predicate exists. So, when is a PMA required? In simple terms: when your device is Class III by regulation or by default, you likely need a PMA unless you successfully petition for reclassification. Class III devices are those for which general controls and special controls are inadequate to assure safety and effectiveness, often because the device is novel and/or critically important to health. For example, implantable pacemakers, heart valves, and other life-supporting devices are designated Class III and thus must go through PMA (except certain pre-1976 devices that temporarily escaped PMA requirements). On the other hand, 510(k) is used for devices that can be categorized as Class II or some Class I – typically devices that have well-understood risks and a predicate on the market. And the De Novo pathway is a one-time route to Class I or II for devices with no predicate, which would otherwise be Class III by default due to novelty. The table below summarizes these pathways:
A PMA is required if your device falls into any of these scenarios:
To illustrate, consider implantable neurostimulators for brain indications (e.g., a brain implant to treat epilepsy). There was no predicate for the first of these, and the risks (invasive brain device) are significant – FDA classified it in Class III. The sponsor had to gather extensive clinical data and submit a PMA. In contrast, a novel fitness wearable sensor (low-to-moderate risk) with no predicate might avoid PMA by using the De Novo route to become Class II, if appropriate controls can manage its risks. The key differentiator is level of risk and available controls: PMA is reserved for when a device’s risk demands comprehensive, case-by-case FDA evaluation rather than a reliance on existing standards or predicates.
From a preparation and regulatory burden standpoint, PMA is far more demanding than a 510(k) or De Novo. A 510(k) submission typically contains performance testing and comparisons to an existing device, and FDA clearance (not “approval”) is based on substantial equivalence. No demonstration of clinical effectiveness is usually required for 510(k). A De Novo submission, while more substantive than a 510(k), is essentially a risk-based classification request where you propose special controls to ensure safety/effectiveness for a new Class II device. PMA, by contrast, requires demonstrating actual clinical safety and effectiveness from your own device’s data. FDA’s decision on a PMA is an affirmative approval that the benefits outweigh the risks for the intended population. PMAs require quality systems information, often an FDA manufacturing inspection, and carry post-approval obligations (like annual reports and potentially postmarket studies) that 510(k) devices do not. The review timelines also differ: 510(k)s by law are reviewed in ~90 days, whereas PMAs have a statutory 180-day FDA review clock (and often involve panel meetings or multiple rounds of questions). De Novo requests have target timelines (often 120-150 days under user fee goals) but can vary. For a startup or international firm, the choice of pathway hugely impacts time, cost, and data requirements. If there is any ambiguity about your device’s classification, one can request FDA feedback via a 513(g) or Pre-Submission meeting to confirm if PMA is required. It’s wise to determine this early: pursuing a 510(k) when a PMA is actually required will waste valuable time.
There are a few special situations to note when distinguishing PMA vs 510(k)/De Novo:
Use the PMA pathway when your device is Class III – i.e., high risk or novel with no other viable controls. Use 510(k) when your device is moderate risk and you can demonstrate it’s substantially equivalent to an existing product. Use De Novo when you have a novel device that isn’t high-risk and you can propose special controls to ensure safety/effectiveness. For startups and global companies, making the correct pathway determination early is critical. PMA is the costliest and lengthiest route, but it’s non-negotiable for truly high-risk devices. On the flip side, pursuing 510(k) or De Novo inappropriately can lead to regulatory setbacks. When in doubt, consult FDA’s classification databases and consider a Pre-Submission meeting to confirm your strategy. Aligning your regulatory path with your device’s risk profile will save you time and resources on the road to FDA approval or clearance.
