FDA 510(k) Glossary · regulatory

Not Substantially Equivalent (NSE)

Not Substantially Equivalent (NSE) is the FDA determination that a 510(k) submission has failed to demonstrate substantial equivalence to a valid predicate device. An NSE determination - decision code DENG - prevents the device from being marketed and requires the manufacturer to pursue an alternative regulatory pathway.
Dataset Insight - 510k Database (166,200 records, 1980–2025)
464 of 166,200 submissions (0.28%) in the dataset received a Not Substantially Equivalent (DENG) determination. NSE rates vary from 0.07% (Dental) to 42% (Medical Genetics).

Definition

A Not Substantially Equivalent (NSE) determination - identified by decision code DENG in the FDA 510(k) database - is issued when the FDA concludes that a submitted device does not meet the substantial equivalence standard required for clearance. It is the only outcome that results in denial of a 510(k) submission.

Grounds for NSE Determination

The FDA may issue an NSE determination when:

  • The new device has a different intended use than the proposed predicate device.
  • The new device has different technological characteristics that raise new questions of safety or effectiveness that the submission has not adequately addressed.
  • The proposed predicate device is itself not legally marketed or is otherwise invalid.
  • The submission contains insufficient data to support a substantial equivalence finding.

NSE Rates by Panel

PanelTotal SubmissionsNSE DecisionsNSE Rate
Medical Genetics19842.1%
Pathology1,099232.1%
Microbiology7,038620.88%
Neurology6,214540.87%
Dental12,53590.07%
Orthopedic17,766170.10%

Options After NSE

  1. Resubmission - file a new 510(k) with a more appropriate predicate or additional supporting data.
  2. De Novo Classification - if the device is low-to-moderate risk and lacks a valid predicate, De Novo may be the appropriate pathway.
  3. Premarket Approval (PMA) - for high-risk devices requiring clinical evidence of safety and effectiveness.

Dataset Insights

Of the 166,200 submissions in the 510k Database dataset, 464 (0.28%) received a Not Substantially Equivalent determination. Search all 510(k) submissions to filter by decision outcome.

FDA References

Related Terms

Substantial Equivalence - Predicate Device - De Novo Classification - 510(k) Premarket Notification

Frequently Asked Questions

A Not Substantially Equivalent (NSE) determination means the FDA has concluded that the submitted device does not meet the substantial equivalence standard. The device either has a different intended use than the predicate, or its different technological characteristics raise new safety or effectiveness questions that the manufacturer has not resolved.

The decision code for a Not Substantially Equivalent determination is DENG. In the 510k Database dataset, 464 of 166,200 submissions (0.28%) carry this decision code. NSE rates vary significantly by FDA review panel - Microbiology has the highest rate with 62 NSE decisions.

After an NSE determination, a manufacturer has three main options: (1) resubmit the 510(k) with a better-suited predicate or additional supporting data; (2) pursue De Novo classification if the device is novel and low-to-moderate risk; or (3) apply for Premarket Approval (PMA) with clinical evidence of safety and effectiveness.

Based on 510k Database records, the panels with the highest NSE rates are Microbiology (62 NSE decisions), Neurology (54), and Gastroenterology/Urology (47). Medical Genetics has the highest rate proportionally - 8 NSE decisions out of only 19 total submissions (42%).