Human Factors Validation Testing plays an important role for medical devices intended to be marketed in the United States. Conducted toward the end of development, it examines how intended users interact with the final user interface under realistic use conditions. The focus is on safety-related tasks and whether the measures intended to reduce use-related risks are actually effective.
But what exactly does the FDA mean by Human Factors Validation? Why is it important for regulatory clearance or approval? What needs to be evaluated in a Human Factors Validation study? And how does Human Factors Validation differ from summative evaluation under IEC 62366-1?
We answer these questions in this article.
1. What is Human Factors Validation according to the FDA?
A key reference for Human Factors Engineering in the US market is the FDA guidance “Applying Human Factors and Usability Engineering to Medical Devices”, updated on August 3, 2026. It describes how manufacturers can identify, reduce, and subsequently evaluate use-related risks throughout product development.
The FDA defines Human Factors Validation Testing as follows:
“Testing conducted at the end of the device development process to assess user interactions with a device user interface to identify use errors that would or could result in serious harm to the patient or user. Human factors validation testing is also used to assess the effectiveness of risk control measures. Human factors validation testing represents one portion of design validation.”
(FDA, Applying Human Factors and Usability Engineering to Medical Devices, Section 3, “Definitions”).
The FDA considers not only potential use errors but also the effectiveness of the intended risk control measures. Under its definition, Human Factors Validation Testing is part of design validation. The assessment therefore considers whether the final user interface design supports safe and effective use.
A simple example: An infusion pump may correctly deliver the dose entered into the device. However, if the user interface makes it easy to confuse input fields, the user might enter an incorrect dose. Human Factors Validation therefore does not retest the pump’s technical functionality; instead, it examines safety-relevant interactions with its user interface.
An important distinction: Validation does not demonstrate absolute freedom from errors. Its results must provide evidence of whether relevant use errors and other use problems occur and what they mean for risk controls and residual risks.
2. Why is Human Factors Validation important?
Human Factors Validation is relevant from a regulatory perspective. The FDA considers Human Factors information during premarket review of medical devices.
Since May 2026, the FDA guidance “Content of Human Factors Information in Medical Device Marketing Submissions” has described a risk-based framework for the human factors information manufacturers should submit, for example, in 510(k), De Novo, or PMA submissions. The FDA distinguishes between Human Factors Engineering carried out during product development and the information submitted for regulatory review.
The information expected in a submission depends, among other factors, on use-related risks and the applicable HF Submission Category. A complete Human Factors Validation study therefore does not automatically need to be submitted with every application.
What does this mean for manufacturers? Human Factors should be integrated into the regulatory strategy early on. If a team waits until just before submission to determine what Human Factors evidence the FDA expects for a particular device, additional testing, documentation work, or requests for information can delay the review process.
Regulatory relevance is only part of the picture. Human Factors Validation is also crucial to safe use. Medical device risks can arise not only from technical malfunctions but also from interactions between users and products.
For example, users might:
- overlook important information,
- misinterpret a setting,
- confuse two controls,
- fail to notice a warning, or
- fail to perform a required action, or perform it too late.
Human Factors Validation helps assess whether these safety-related problems still occur with the final design and whether the intended risk control measures are sufficiently effective.
Validation also has direct implications for project planning. If fundamental problems only emerge at this late stage, the necessary changes may affect more than the user interface. They can also affect risk management, labeling, instructions for use (IFU), training, technical documentation, or further verification and validation activities.
3. What is evaluated during Human Factors Validation?
The FDA considers the interaction between users, use environments, and the user interface. For validation results to be meaningful, all three must reflect the device’s intended use. Critical tasks identified through risk management and appropriate data collection are also essential.
3.1. Intended Users
Human Factors Validation participants must represent the device’s actual intended user populations. Depending on the medical device, these may include physicians, nurses, laboratory personnel, service technicians, patients, caregivers, or other lay users.
Professional roles are not the only relevant characteristics. Age, experience, knowledge, and physical, sensory, or cognitive abilities may also affect interactions with a medical device and should be considered as appropriate.
The FDA generally recommends at least 15 participants per distinct user population for Human Factors Validation Testing. Whether user populations should be assessed separately depends in particular on whether their characteristics or tasks meaningfully affect their interactions with the device.
Study planning should be informed by previous analyses and evaluations. A larger sample may be appropriate for certain medical devices.
If a study is intended to demonstrate safe and effective use by users in the United States, FDA recommendations generally call for participants who reside in the United States. Studies involving participants outside the United States may be considered on a case-by-case basis with appropriate justification.
3.2. Intended Use Conditions
Testing should reflect the conditions that actually influence safe use. These may include noise, lighting, distractions, time pressure, interruptions, or the simultaneous operation of multiple devices.
The relevant factors depend on the intended use environments and the risk analysis. A medical device used in an intensive care unit, for example, places different demands on the test environment than a device patients use independently at home.
Realistic simulated use is often sufficient. However, if important interactions cannot be adequately evaluated in a simulation, testing under actual use conditions may be necessary.
3.3. The final User Interface – Including IFU and Training
Under the FDA’s understanding, the user interface encompasses all points of interaction between the user and the device. These include not only displays, software, and physical controls but, as applicable, also warnings, packaging, labeling, instructions for use (IFU), and training materials.
The user interface used in validation should represent the final design. Information and training should realistically reflect how the device will be used after launch. For example, if no training will be provided in practice, giving all study participants additional training would not be representative. Where training is intended, its content, delivery, and – where relevant – an appropriate interval between training and testing should be considered.
Caution is particularly warranted when it comes to IFU and training: If safety-related content is changed following validation, simply claiming that the change will resolve the issue is not sufficient. Its effectiveness must be demonstrated, if necessary, through additional, appropriate evidence.
3.4. Critical Task
Human Factors Validation places particular emphasis on so-called critical tasks.
Critical tasks are especially important when determining study content. The FDA describes a critical task in the guidance “Applying Human Factors and Usability Engineering to Medical Devices” as follows:
“A user task that, if performed incorrectly or not performed at all, would or could cause serious harm to the patient or user, where harm is defined to include compromised medical care.”
(FDA, Applying Human Factors and Usability Engineering to Medical Devices, Section 3, “Definitions”).
The decisive factor is not how frequently a task is performed but what consequences incorrect performance – or failure to perform it – could have. Under the FDA definition, harm expressly includes compromised medical care.
A simple example: Entering the correct medication dose into an infusion pump may be a critical task. If an incorrect entry could lead to over- or underdosing with serious consequences, the task must be addressed in Human Factors Validation.
Critical tasks are derived from use-related risks before validation. The use-related risk analysis (URRA) is an important foundation. It should take into account findings from task analysis, known use problems, appropriate risk analysis methods, expert reviews, and formative evaluations, among other sources. A use-related FMEA (uFMEA) can be an important documentation method, but it is not automatically equivalent to the entire URRA.
The FDA expects all identified critical tasks to be addressed during Human Factors Validation Testing. At the same time, the test workflow should be as natural as possible and allow previously unanticipated use errors to emerge.
3.5. Data Collection
Simply asking participants after the test whether they found the device easy to use does not provide a sufficiently robust assessment. The FDA distinguishes three complementary types of data in Human Factors Validation Testing:
- Observational Data: Observations of actual task performance, particularly use errors, close calls (errors that are caught or avoided before leading to harm), and use difficulties such as hesitation, repeated attempts, or apparent confusion.
- Knowledge Task Data: Assessment of safety-related knowledge that cannot reasonably be evaluated by observing an action – for example, understanding specific warnings or contraindications. Open-ended, neutral questions are suitable for this purpose.
- Interview Data: Follow-up interviews to understand participants’ perspectives on observed errors, difficulties, and their possible causes.
Each data type serves a different purpose. Interviews cannot replace observation when correct task performance can be assessed directly. Participants should also be able to act with minimal interference during simulated validation testing. Unlike in many formative studies, facilitated “think-aloud” during task performance is not appropriate here.
Only by analyzing observations, knowledge questions, and interviews together can the team assess why a use problem occurred, what risk it represents, and whether additional risk control measures or repeat validation are necessary.
4. How does Human Factors Validation differ from summative Evaluation?
The IEC 62366-1:2015, including Amendment 1:2020 describes a usability engineering process for medical devices with a focus on safe use. In summative evaluation, the hazard-related use scenarios defined according to the normative selection procedure are evaluated on the final or production-equivalent user interface. The selection may be based, among other factors, on the severity of potential harm.
The FDA places particular emphasis on previously identified critical tasks in Human Factors Validation Testing and provides detailed recommendations concerning user populations, realistic test conditions, the final user interface, and data collection and analysis. The FDA itself notes that Human Factors Validation Testing is sometimes called “summative testing,” but that the terms do not always cover the same scope.
In practice, three distinctions are especially important:
- Selection of test content: selected hazard-related use scenarios under IEC 62366-1 versus identified critical tasks under FDA guidance;
- Study design: regulatory expectations for participants, use context, labeling, training, and data collection;
- Supporting evidence: different requirements and recommendations concerning risk traceability, justifications, and documentation for the target market.
IEC 62366-1 is not an exclusively European standard. It may also be relevant to development for the US market. Conversely, calling a study a “summative evaluation” does not in itself demonstrate that the FDA’s recommendations have been met.
Can one study serve both the EU and US markets? Yes, under suitable conditions. The study design must be planned from the outset to address the relevant requirements for both markets. A completed study cannot automatically be used for both markets without further assessment.
Conclusion
Human Factors Validation provides important evidence of whether the final user interface supports safe and effective use by intended users. The scope of evidence needed, and what should be submitted to the FDA, depend on the specific medical device and its use-related risks.
We therefore recommend clarifying three points early in planning: Which users and use conditions are relevant? Which tasks or scenarios are safety-critical? And what evidence is needed for the intended markets? This allows risk management, study planning, and the regulatory strategy to be aligned effectively.
Are you still unsure whether your device needs a summative evaluation, Human Factors Validation, or potentially both? In our on-demand webinar “Do You Really Need a Summative Evaluation or Human Factors Validation?” we explore typical decision-making situations and practical criteria
