IEC 62366-1 is the international standard for applying usability engineering to medical devices. FDA recognizes it as a consensus standard, and compliance is effectively required for market clearance in the US and CE marking in Europe. This guide explains what the standard requires, how it translates into practical study planning, and what your facility and recruitment setup needs to support it.
The standard defines a usability engineering process that runs in parallel with your product development lifecycle. The core steps: prepare a use specification (intended users, use environments, user interface), identify use-related hazards, identify and categorize hazard-related use scenarios, establish a user interface specification, plan and conduct formative evaluations (iterative), plan and conduct summative evaluation (validation), and compile the usability engineering file (UEF).
The key output is the UEF — the documentation package that demonstrates your usability engineering process to regulators. It must trace the full process from use specification through validation results.
Formative evaluations are iterative studies conducted during design and development. The goal is to identify usability issues while changes are still feasible and affordable. There is no minimum participant requirement — formative studies can be conducted with as few as 5-8 participants per round.
Low-fidelity prototypes, paper mockups, and early software builds are all appropriate test stimuli. Multiple rounds of formative testing are typical. Each round reveals issues, the design team addresses them, and the next round validates improvements while uncovering new issues.
Formative studies can be conducted in standard usability labs without simulated clinical environments, though realistic conditions improve the quality of findings.
Summative evaluation is the formal, final assessment that demonstrates your device can be used safely and effectively. It tests the finished or near-finished device with representative users in a simulated use environment.
FDA expects a minimum of 15 participants per user group. The study evaluates all hazard-related use scenarios identified in your risk analysis. Results must demonstrate that residual use-related risks are acceptable.
This is the study your 510(k) or PMA reviewer will scrutinize most closely.
The IEC 62366-1 process drives specific infrastructure requirements that most companies need external support for.
Formative studies need flexible lab space, basic A/V recording, and access to representative users for iterative rounds of testing. Summative studies need purpose-built facilities with one-way observation, HD recording, and configurable room layouts that can simulate the intended use environment.
Recruitment needs to produce participants who genuinely represent the intended user groups defined in your use specification — screened and qualified against your inclusion/exclusion criteria.
For clinical device summative studies, this typically means recruiting licensed healthcare professionals from the relevant specialties, in the relevant clinical settings, with the relevant experience levels.
FDA recognizes IEC 62366-1 as a consensus standard but also publishes its own guidance: "Applying Human Factors and Usability Engineering to Medical Devices." The two frameworks overlap heavily, but the FDA guidance is more prescriptive in several areas.
The biggest difference is around critical tasks. IEC 62366-1 uses the term "hazard-related use scenarios" and ties them to the risk management process. FDA expects you to explicitly identify "critical tasks" and justify why each one is or isn't included in your validation study. Reviewers want a clear table mapping each critical task to its test scenario, success criteria, and results.
FDA also expects more detail in the validation report itself: individual participant-level data (not just aggregate pass/fail rates), root cause analysis for every observed use error on a critical task, and a narrative argument that residual risk is acceptable. IEC 62366-1 requires these elements conceptually, but FDA reviewers want them in a specific structure they can audit quickly.
If you're submitting to FDA, follow both. Design your study to satisfy the standard, then document it in the format FDA reviewers expect.
Most teams don't need help understanding the standard. They need help executing it. The labs, the participants, the scheduling, the recording setup. That's what we do. Reach out and tell us where you are in the process.
We support formative and summative studies for teams at every stage of the 62366 process.
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