On May 28, 2026, the FDA published the final version of its guidance “Content of Human Factors Information in Medical Device Marketing Submissions.” This finalization, four years after the 2022 draft, brings significant changes to how manufacturers must document and present human factors (HF) information in 510(k), De Novo, PMA, and HDE applications.
If you are currently preparing a premarket submission, or have one under FDA review, the decisions you make about your human factors documentation in the coming weeks will directly affect your timeline. This article breaks down what changed, what it means in practice, and where manufacturers typically get it wrong, based on over 50 usability projects, approximately 10 of which involved FDA submissions specifically.
Note: The FDA has confirmed that submissions received before August 1, 2026 may not yet include all newly recommended information. However, FDA will review any additional HF information voluntarily submitted during this transition period.
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What Changed from the 2022 Draft to the 2026 Final Guidance
The foundational risk-based framework introduced in the 2022 draft remains intact. Manufacturers still determine their HF Submission Category (1, 2, or 3) using a decision flowchart, and the three-category structure governs what documentation must accompany the submission.
However, the final guidance introduces several refinements that matter significantly in practice:
A New Decision Point D in the Category Flowchart
The most impactful structural change is the addition of Decision Point D. When determining the submission category, manufacturers must now explicitly consider:
- The user interface (UI) use history of the device
- User familiarity with the device or similar devices
- The adequacy of existing risk mitigations already in place
This is particularly relevant for modified devices where prior FDA clearances or approvals exist. For established products with well-documented use history and low rates of use-related adverse events, Decision Point D may allow manufacturers to justify a lower submission category without new summative testing.
For completely new devices, the approach is different and could be based on the level of novelty, complexity of the user interfaces and the similarity to other legally marketed devices with the same intended use. In those cases, a strong rationale shall be provide to describe the basis of the decision to not include human factors validation study data. For devices, with no use history or as a result of the subject device’s novel user interface, the Use-Related Risk Analysis (URRA) and Human Factors validation protocol become the primary tools for demonstrating that the decision is grounded in objective evidence, not simply assumed.
Reorganized HFE/UE Report Outline
The final guidance solidifies a new report structure that switches the order of Sections 5 and 6 compared to the 2016 guidance. The new sequence places the summary of preliminary (formative) evaluations before two consecutive sections on the URRA and critical task identification.
This change is not cosmetic. The revised order forces a more coherent narrative: what did you learn in early development, how did that shape your risk picture, and what critical tasks emerged from that process. FDA reviewers can now trace the logic of your HF work from evidence to risk to testing, rather than having to reconstruct it from disconnected sections.
Manufacturers who continue to follow the 2016 report outline in submissions after August 2026 will likely face Additional Information (AI) requests asking them to restructure the HFE/UE report.
Detailed Report outlines in Three New Appendices
The final guidance adds three appendices providing sample HFE/UE report content for Category 1, Category 2, and Category 3 submissions. These are not hypothetical, they represent the level of specificity FDA now expects manufacturers to match in their own documentation.
Expended set of practical examples
The final version contains a series of examples; such as a reusable duodenoscope, a stereotaxic navigation system, a continuous glucose monitor (CGM), and an interoperable automated glycemic controller; illustrating the FDA’s reasoning in various contexts: modification of an algorithm without affecting the user interface, updating of labelling, modification or addition of a user interface, or extension to a paediatric population.
These examples provide significant added value, as they help to better understand the practical implementation of the principles set out. Whilst the general regulatory logic is relatively clear, its interpretation in the context of a specific change often remains a source of uncertainty. The cases presented thus help to reduce this grey area and give the final version a more practical focus than the initial draft guidance.
The Three HF Submission Categories Explained
Correctly identifying the applicable category is the foundation of your entire HF submission strategy. A misclassified category does not just create paperwork problems, it can add months to your submission timeline.
Category 1: Modifications That Do Not Affect Human Factors Considerations
Category 1 applies when a device modification has no impact on the user interface, use specification or training and labeling. The submission requires only a conclusion and high-level summary justifying that the modifications do not affect HF considerations, plus any prior HFE/UE evaluations being leveraged.
Category 1 is the most commonly misassigned category. Manufacturers frequently overlook that the user interface extends beyond the physical device. A change to the Instructions for Use (IFU) or the product label can directly affect how users perform critical tasks, and that modification triggers a higher category, regardless of how minor the change appears on paper.
Category 2: Modifications Without New or Impacted Critical Tasks
Category 2 applies when modifications affect the UI but do not introduce or modify critical tasks, tasks where a use error could directly cause or contribute to serious harm. In addition to the Category 1 summary, submissions must include descriptions of intended users, use environments, and training (Section 2), a device user-interface description (Section 3), and a summary of known use problems (Section 4).
The boundary between Category 2 and Category 3 is often where the most consequential misclassification errors occur. Manufacturers underestimate the downstream impact of a UI modification on critical tasks, particularly in complex devices where multiple tasks interact.
Category 3: Critical Tasks Introduced or Modified
Category 3 is required when the device has critical tasks or when modifications create new critical tasks or affect existing ones. This is the most documentation-intensive category, requiring the full HFE/UE report including the URRA, critical task identification, human factors validation testing and the complete report structure described in the final guidance.
A misclassification into Category 2 when Category 3 is actually required is among the most costly errors in the submission process. Based on experience across usability projects, remediation that requires a new human factors validation study adds a minimum of 3 to 4 months to the submission timeline. When the FDA also identifies issues with other parts of the usability process, incomplete user group representation, misaligned URRA, insufficient critical task identification, the delays can extend well beyond that.
The Most Common Mistakes in Human Factors Submissions
The following observations come from direct experience across more than 50 usability projects, approximately 10 of which involved FDA submissions. These are not theoretical risks, they are patterns that recur across manufacturers of different sizes and device types.
Mistake 1: Treating the IFU and Label as Outside the User Interface
This is the most common error in category determination. Manufacturers focus on the physical device or software interface when assessing whether a modification affects the UI. They do not apply the same scrutiny to changes in labeling and Instructions for Use.
Under the final guidance, consistent with ANSI/AAMI/IEC 62366-1, labeling and training are explicitly defined as subsets of the user interface. A modification to the IFU wording, the layout of a label, the sequence of instructions, or even the font size used in safety warnings can directly affect how users perform critical tasks.
The consequence is a Category 1 or Category 2 assignment when Category 3 is required. When FDA identifies this during review, the manufacturer must go back and perform human factors validation testing, adding months to the process.
Mistake 2: Underestimating the Impact of a Modification on Critical Tasks
Even when manufacturers correctly identify the physical UI elements involved in a modification, they frequently underestimate the downstream effects on critical tasks. A change to a device’s alert mechanism, for example, may not seem to directly touch a critical task, but if that alert is the primary signal that prompts a user to take a safety-critical action, the modification has introduced or modified a critical task whether the manufacturer acknowledges it or not.
This error also surfaces in remediation projects. In one case involving a device where not all user groups had been included in the original critical task identification, the team had to restart the process to cover the full product lifecycle. This included identifying all critical tasks for the previously uncovered user group, then conducting both formative and human factors validation testing with new participants. The result was an 8-month delay before the submission could move forward.
Mistake 3: URRA Not Aligned with Summative Testing
The Use-Related Risk Analysis is the backbone of the HF submission. Critical tasks in the Human Factors Validation Testing must trace directly to hazards and use errors identified in the URRA, and the URRA must cover the full use lifecycle, not just the most visible or technically complex interactions.
When the URRA is incomplete or misaligned with the summative protocol, FDA can identify the gap during review and require additional testing. Because summative testing involves recruiting representative user groups, designing and executing validated protocols, and processing results against pre-defined acceptance criteria, this remediation cycle rarely takes less than 3 to 4 months.
Practical Guidance: What to Do if Your Submission Is Already Under Review
The final guidance explicitly states that submissions received before August 1, 2026 may not yet include all newly recommended information. FDA has confirmed it will review any additional HF information voluntarily submitted during this period.
Whether to submit additional information proactively depends on the specific circumstances of your device and submission:
- If your device is a modification: assess whether any critical tasks were created, modified, or affected by the change. If there is any doubt, submitting additional URRA documentation that addresses Decision Point D is a defensible and low-risk step.
- If your device is new: evaluate whether the HFE/UE report follows the revised outline from the final guidance. If it follows the 2016 structure, consider whether proactively restructuring the relevant sections, particularly around the URRA and critical task sequencing, is feasible within the review timeline.
- In all cases: prioritize the approach that best reflects the actual safety risk profile of the device. The guidance is risk-based; the FDA’s expectation is that manufacturers apply the same logic.
If you are uncertain, consulting with a human factors specialist before making a voluntary submission is strongly advisable. An incorrectly framed addition can raise new questions rather than resolve existing ones.
How This Affects Wearable Devices
Wearable devices present a particular challenge for human factors engineering because the intended user population is typically patients or caregivers at home, without formal clinical training, operating in variable and often unpredictable environments.
In practice, the use scenarios most frequently missed in wearable device submissions involve interactions that seem straightforward but carry real risk when performed incorrectly in a home context:
Result Interpretation
Users misread or misinterpret displayed results, due to unclear wording, unfamiliar units, or poor visual hierarchy on small screens. This is among the most frequently identified use errors in wearable submissions. A user who misunderstands what a measurement means may fail to seek care when they should, or seek unnecessary care when they should not. Both are clinically consequential outcomes.
The critical task here is not simply ‘read the display’, it is ‘correctly interpret the result and take the appropriate action.’ That distinction matters for how the task is defined in the URRA and tested in the human factors validation study.
Battery Replacement
Seemingly minor maintenance tasks, such as replacing a battery, can become critical tasks in wearables if an incorrect replacement leads to device failure at a moment when the device result is needed. In home-use devices, the user has no backup procedure and no trained support immediately available. Manufacturers frequently assign this scenario to a non-critical category without testing whether the replacement procedure is reliably executed by their intended user population.
Both examples illustrate a broader principle: the use environment impacts the user interface. A task that is safely executed in a clinical setting with trained personnel may not be safely executed by a patient at home under stress, in poor lighting, or without reading the IFU a second time.
Aligning FDA and IEC 62366: A Dual-Market Strategy
Many manufacturers pursuing simultaneous FDA and EU MDR/IVDR compliance ask whether a single usability program can satisfy both frameworks. The short answer is: yes, with deliberate planning, but only if the program is designed for both markets from the outset, not adapted for the second market after the fact.
The core activities, user research, formative evaluation, summative validation, are required by both frameworks. The differences lie in specific requirements and terminology:
| FDA Requirement | IEC 62366 / EU Equivalent |
|---|---|
| Critical tasks | Hazard-related use scenarios |
| Human factors Validation | Summative evaluation |
| Human factors validation testing data | Evidence from summative evaluation |
| US-resident participants required | No residency requirement; local language required |
| URRA as primary risk document | Hazard-related use scenario analysis within risk management |
The most important structural question in a dual-market program is whether the intended user groups across the two markets share the same characteristics and operate in the same use environments. If they do not, separate or supplemental testing may be required for one market.
One area where FDA and IEC 62366 diverge operationally: FDA requires US-resident participants for Human Factors Validation studies, while IEC 62366-1 submissions have no residency requirement but may require testing in local languages. A Human Factors Validation testing conducted in the US with US-resident participants can support the FDA submission and, with an appropriate rationale linking the use specification to the EU context, can often also be leveraged for the IEC 62366 summative evaluation report.
The Use-Related Risk Analysis can be structured to satisfy both frameworks simultaneously. Building a URRA that maps hazard-related use scenarios to critical tasks from the outset, rather than creating separate documents for each market, significantly reduces the documentation burden across the program.
What to Expect Over the Next 12 Months
The transition to the final guidance will not be immediate. Based on experience with prior guidance transitions and the pattern of FDA reviewer adoption, the following issues are most likely to emerge in submissions over the next 12 months:
- Manufacturers will continue submitting HFE/UE reports following the 2016 outline. Until the revised structure becomes standard practice, AI requests asking for restructured reports will increase.
- The use of UI use history data to justify lower HF submission categories will be poorly documented. Decision Point D is new and requires a specific type of rationale that most manufacturers have not written before. Submissions that assert a lower category based on use history without providing objective supporting evidence will face pushback.
- The new appendix examples will raise the bar for what reviewers consider adequate documentation. Manufacturers who previously submitted sparse Category 2 reports will find that FDA reviewers now have concrete reference examples against which to compare submissions.
Frequently Asked Questions
The FDA’s human factors guidance for medical devices is a set of recommendations on what human factors (HF) information manufacturers must include in premarket submissions, specifically 510(k), De Novo, PMA, and HDE applications. The final guidance, published May 28, 2026, provides a risk-based framework that categorizes devices into three submission categories depending on whether modifications affect critical tasks and use-related hazards.
A Category 3 device under the Human Factors (HF) regulations is either a device where modifications have resulted in new critical tasks or have had a significant impact on existing critical tasks, or a new device involving critical tasks, i.e. tasks where an error in use could directly cause or contribute to serious harm. Category 3 requires the most comprehensive HF documentation, including, in particular, a comprehensive HFE/UE report, an analysis of risks associated with use, the identification of critical tasks, and human factors validation test data.
The FDA human factors guidance formally applies to devices regulated by CDRH, which includes in vitro diagnostic devices (IVDs). IVDs used in laboratory settings have distinct human factors considerations, particularly around critical task definition when the device is operated by lab technicians but the result directly affects clinical treatment decisions. Manufacturers of IVDs submitting to CDRH should apply the same category determination framework as any other medical device.
A critical task is a user task which, if performed incorrectly or not performed at all, could directly cause or contribute to serious harm. Critical tasks are identified through the Use-Related Risk Analysis (URRA) and form the basis for human factors validation testing. Correctly identifying all critical tasks, including those arising from labeling, IFU changes, and maintenance operations, is one of the most consequential steps in the human factors engineering process.
FDA human factors engineering and IEC 62366 usability engineering cover the same fundamental activities, user research, formative evaluation, summative validation, using different terminology. FDA refers to ‘critical tasks’ where IEC 62366 uses ‘hazard-related use scenarios’; FDA calls the validation study a ‘human factors validation testing’ where IEC 62366 calls it a ‘summative evaluation.’ Both frameworks require representative user group participation and risk-based documentation. Dual-market programs can be designed to satisfy both simultaneously, with the URRA structured to map to both sets of requirements.
Incorrectly assigning a lower submission category than required typically results in an FDA Additional Information (AI) request requiring additional human factors documentation, which may include new summative validation testing. Performing a new human factors validation study, recruiting representative participants, executing the protocol, and processing results, adds a minimum of 3 to 4 months to the submission timeline, and more if the FDA also identifies issues in other parts of the usability process.
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Our usability engineering services cover the full product lifecycle, including IEC 62366 compliance for EU MDR and IVDR, FDA human factors guidance alignment, and dual-market documentation strategies.
