FDA’s human factors and usability engineering guidance requires device makers to run a use-related risk analysis, complete iterative formative usability testing during design, and pass a final summative validation test proving intended users can operate the device safely. FDA expects this human factors data in PMA, De Novo, and many 510(k) submissions where a use error could cause serious harm.
What the guidance is
“Applying Human Factors and Usability Engineering to Medical Devices” is FDA’s final guidance document, issued February 3, 2016 by the Center for Devices and Radiological Health (CDRH), on incorporating human factors (HF) engineering into medical device design and premarket review. It finalized a 2011 draft and formally superseded FDA’s earlier 2000 guidance, “Medical Device Use-Safety: Incorporating Human Factors Engineering into Risk Management.” The guidance sets out FDA’s expectations for a documented usability engineering process spanning early design through final validation, applicable to both standalone devices and the device-user-interface elements of combination products.
The premise behind the guidance is straightforward: many device-related adverse events are not caused by a mechanical or software failure but by a user – a clinician, caregiver, or patient – performing a task incorrectly because the interface, labeling, or workflow made the correct action difficult to identify or execute. FDA’s usability engineering process is designed to find and mitigate those use-related hazards before a device reaches the market, rather than relying on post-market adverse event reports to surface them.
The core process FDA expects
Use-related risk analysis
The process starts with a use-related risk analysis: mapping every user task involved in operating the device, then identifying which tasks are “critical tasks” – defined as tasks that, if performed incorrectly or not performed at all, would or could cause serious harm to the patient or user. Critical tasks are the focus of the rest of the usability engineering effort; FDA expects manufacturers to justify why a task was or was not classified as critical.
Formative usability testing
Formative evaluations are iterative usability assessments conducted throughout design and development – they can include expert reviews, heuristic analysis, and usability tests with representative users on early prototypes. Their purpose is to identify use problems and interface weaknesses early enough to redesign around them. Notably, FDA’s guidance expects documented formative testing to occur before summative testing even where IEC 62366-1 itself does not explicitly mandate it – this is one of the points where the FDA guidance goes beyond the international standard’s literal requirements.
Summative usability testing (human factors validation)
Summative testing is the final, formal human factors validation study: representative users, from the intended user population(s), performing critical tasks with the final (or equivalent) device design, in a simulated or actual use environment, without coaching from study staff beyond what real-world labeling and training would provide. The goal is to demonstrate that use errors and close calls involving critical tasks either did not occur or, if they did, did not result in unacceptable risk of harm – and to analyze the root cause of any that did occur.
Which submissions require human factors data
FDA does not require a formal human factors validation study for every device, but expects it wherever a use error involving a critical task could cause serious harm. In practice this means:
- PMA and De Novo submissions for higher-risk devices routinely need a full human factors engineering (HFE) report, including use-related risk analysis, summary of formative findings, and summative validation results.
- 510(k) submissions need human factors data when the device has one or more critical tasks, a new or modified user interface compared to the predicate, a history of use-related adverse events for similar devices, or is intended for use by lay users, in the home, or in a high-stress/high-workload clinical environment.
- Combination products (drug-device or biologic-device combinations, e.g. autoinjectors, prefilled syringes with add-on delivery mechanisms) are addressed by a related FDA guidance on human factors studies for combination products, which layers device-style usability engineering onto the human factors expectations for the drug-delivery interface.
This sits alongside, and often within, the broader device submission pathways covered in CASRAI’s FDA 510(k) Premarket Notification guide: human factors data is one of the technical sections a 510(k) or PMA reviewer will look for, not a separate submission type of its own.
Relationship to IEC 62366-1
ANSI/AAMI/IEC 62366-1:2015, Medical devices – Application of usability engineering to medical devices, is the internationally harmonized standard covering the same underlying process: use specification, use-related risk analysis, formative evaluation, and summative validation. FDA has listed IEC 62366-1 among its FDA-recognized consensus standards, meaning a manufacturer that follows it correctly and cites it in a submission can use that as supporting evidence of an acceptable usability engineering process.
Recognition is not full equivalence, however. FDA’s own guidance is more prescriptive in places – for example, its explicit expectation of iterative formative testing before summative validation, and its specific expectations for what a submission’s human factors engineering report must contain (use-related risk analysis, task list with critical-task determinations, formative test summaries, and the summative protocol and results with root-cause analysis of any use errors observed). Manufacturers preparing a U.S. submission generally need to satisfy both the standard’s process requirements and FDA’s own documentation and reporting expectations, not treat compliance with one as automatically satisfying the other.
Frequently asked questions
What counts as a “critical task” under FDA’s human factors guidance?
A critical task is a user task that, if performed incorrectly or omitted, would or could cause serious harm to the patient or user, where “serious harm” is not limited to death but includes harm requiring medical or surgical intervention to preclude permanent impairment. Manufacturers identify critical tasks through the use-related risk analysis and must be prepared to justify the classification in a submission.
How is formative testing different from summative testing?
Formative testing is diagnostic and iterative – it happens throughout design to find and fix usability problems, often on early prototypes, and can use a variety of methods including expert review and small-sample usability testing. Summative testing is confirmatory and happens once at the end, on the final (or equivalent) design, with a defined protocol, a representative user sample, and no coaching, specifically to validate that the device can be used safely by its intended users.
Does every medical device submission need a human factors validation study?
No. FDA expects human factors data in proportion to use-related risk. Devices with no critical tasks, or with a well-established, unchanged user interface and no history of use-related problems, may not need a full summative study – but the underlying use-related risk analysis is still expected as part of design controls under 21 CFR 820.30.
Where does human factors engineering fit relative to design controls generally?
Human factors and usability engineering is a specialized application of the design controls requirements in 21 CFR 820.30 (design input, verification, and validation), focused specifically on the user-device interface and use-related risk rather than device performance more broadly. It is documented and reviewed alongside, not instead of, the rest of a device’s design history file.
