Most medical device manufacturers start their consultation with me asking one of two questions: “Do we need a human factors validation study?” or “How should we do the study?” While important, neither question addresses the more fundamental consideration for regulatory submission success.
The FDA's 2026 human factors content guidance for medical device marketing submissions, now built into the eSTAR v7.0 electronic submission template, doesn't really ask whether you tested the device. It asks whether the device’s use-related risk is deemed acceptable. A validation study is one possible output of that process, not the process itself. If foreseeable misuse of your device could result in severe harm to the user or patient, validation testing is typically needed to demonstrate that risk controls are effective. If not, the justification should be documented within the usability engineering file. Either way, the FDA wants to see the full usability engineering process, not just a test report.
For manufacturers who have not previously been required to submit human factors validation studies, this often means additional documentation will be needed for future submissions for the same type of device. For manufacturers who treat human factors as a late-stage deliverable, that's a real shift in what "ready to submit" means.
Why risk category, not device type, drives the requirement
The FDA categorizes medical device risk into three classes:
- Category 1 generally covers modifications to existing devices that do not affect the user interface, intended users, intended uses, use environment, training or labeling. This often entails modifications that are only in the backend. For example, if a manufacturer has a previously cleared automated radiological image processing software device and the new submission includes only an algorithm update with no changes to the user interface, user tasks or workflow, the device would likely be considered Category 1.
- Category 2 is broader and covers all devices for which a human factors validation study is not warranted. This includes both new devices with no critical tasks and modified devices for which the modification does not impact any critical tasks. It also includes devices that do have critical tasks, but the sponsor can justify not submitting new human factors validation data based on interface history, complexity and existing risk controls.
- Category 3 covers new devices with critical tasks and modifications that have an impact on critical tasks. Critical tasks are those where a misuse could result in severe harm to the user or the patient. This is when human factors validation test data should be submitted.
The distinction between Category 2 and Category 3 is of particular interest to manufacturers because it directly influences the level of human factors evaluation and supporting documentation expected in a regulatory submission.
It is worth mentioning that a device can transition from Category 2 to 3 as a result of modification. Take a home-use in vitro diagnostic as an example. If a patient misreads a test at home, a false positive might cause them to seek medical care unnecessarily; a false negative might delay care modestly. If the delay only results in prolonged discomfort, the test interpretation may not be a critical task that warrants human factors validation.
\When a device modification changes the intended user from home users to clinical users, misreading the result may have very different consequences, depending on who uses the device, the clinical context and how the result influences patient care. In some cases, this use error may lead to severe harm, including misdiagnosis or the introduction of diagnostic confounders, which would make the result interpretation a critical task. The device would be Category 3 in this case if the result interface is different from the standard of care and could confuse clinical users. If the result presentation is similar to standard of care, a manufacturer could provide additional evidence to justify the device being Category 2 based on simplicity of interface.
Human factors submission categories are determined primarily by the potential for use-related harm and the impact of user interactions on device safety and effectiveness, rather than by product code or prior regulatory precedent.
What the FDA wants as proof
For a Category 2 claim, the burden of proof sits with the sponsor, and it doesn't rest on assertion alone. FDA expects a detailed use specification outlining the intended use, intended user, intended use environment and training required of each Category 2 device. A Use-Related Risk Analysis (URRA) is now expected for nearly every new device, including types that historically did not need to submit human factors-related materials. A known use problem search report (KUPS), which identifies foreseeable misuses of similar devices from public databases, is also required as evidence to support the human factors submission category of a new device. Beyond that, formative data or clinician testimony that device use aligns with existing standard of care can carry real weight, particularly for surgical, radiology and cardiology devices for which clinicians are already trained to interpret similar outputs. For modified devices, a comparative analysis of the user tasks, user interface, use specification change and risk controls is increasingly the evidence the FDA expects, rather than an assertion that "nothing significant changed."
When clinical data can double as usability evidence
There are cases when the FDA will accept human factor validation incorporated into a clinical study in place of a standalone usability study — but only under specific conditions. The usability protocol needs to be built into the clinical study design in advance, not added retroactively. User interaction must reflect real-world use; over-training participants beyond what a typical user would receive undermines the value of the data.
Users need to be observed for any usability evaluation. If the clinical study does not allow users to be observed while using the device, additional observational data should be provided to supplement users’ self-reported use errors and adverse events. And this path tends to work best where simulated use testing genuinely can't realistically replicate the actual use scenario — ablation devices that rely on instant visual feedback of tissue coloration to confirm correct use, or surgical tools used on a beating heart, for example — where a bench model or cadaver simply won't produce a realistic result.
What to do if you're submitting soon
If your submission is 30 to 90 days out, there isn't time for a pre-submission meeting. Instead, the priority should be to ensure that your design and development documentation reflects a robust usability engineering process, rather than relying solely on a human factors validation report. Key elements include a complete and well-supported URRA and a comprehensive review of FDA adverse event data for comparable devices. Reports of serious use-related harm from similar products may weaken the rationale for a Category 2 classification, and in some cases, support the need for human factors validation testing as a more defensible regulatory strategy.
For teams already preparing a submission under a legacy human factors approach, now is the time to reassess the design and development file against FDA's updated documentation expectations rather than waiting for a deficiency letter. For modified devices, FDA may expect a comparative user interface analysis even when the changes appear unlikely to introduce new use-related risks. Addressing these gaps during the review process is possible, but doing so can result in avoidable delays that are better mitigated before submission.
The underlying expectation hasn't changed. FDA has always expected manufacturers to demonstrate that their devices can be used safely and effectively. What's changed is that manufacturers now must show their work.
Concerned your human factors documentation may not align with current FDA expectations? IQVIA MedTech's regulatory and human factors specialists help medical device and IVD manufacturers assess submission readiness, identify documentation gaps and develop evidence strategies tailored to their device and risk profile. Learn more about IQVIA MedTech IVD specialized teams.
