The Standard That Treats a Use Error as a Design Failure, Not a User’s.
IEC 62366-1 usability engineering — a process that finds the ways your device will be used wrong and designs them out, with the formative and summative evidence FDA and Notified Bodies expect to see.
Usability Engineering Is a Chain. Summative Validation Is Where It’s Judged.
IEC 62366-1 defines a process that runs from understanding the use through proving the design is safe to use. Skip the early links and the final one — summative validation — has nothing to stand on.
Use Specification
Who uses it, for what, where, and on whom — the intended users, uses, and environments.
UI Specification
The user interface defined against that use — the design the rest of the process evaluates.
Use-Related Risk
The hazard-related use scenarios and use errors that could lead to harm, drawn from the risk file.
Formative Evaluation
Iterative testing during design that finds and fixes use problems while change is still cheap.
Summative Validation
The final human-factors validation that demonstrates the design is safe to use.
Find Problems While They’re Cheap
Formative studies are diagnostic: run early and often, they surface use errors when the fix is a design tweak. Skipping them doesn’t save time — it defers the failure to summative, where it costs a redesign and a re-test.
Prove It, With the Right Users
Summative validation must use representative users, realistic use environments, and the scenarios tied to your critical tasks. FDA’s human-factors expectations are specific — a study designed loosely is a study repeated.
62366 Isn’t About Whether Users Like It. It’s About Whether They Can Harm Someone.
Usability engineering under IEC 62366-1 is a safety process, not a satisfaction survey. It asks a specific question: what are the ways this device could be used incorrectly, and could any of them lead to harm? The answer drives design changes — and the evidence that the design is safe to use is a required part of the file for FDA and Notified Bodies alike.
The connection that makes it work is to risk management. Use-related hazards flow from the ISO 14971 risk analysis; the mitigations flow back into it. 62366 without a live risk file is a study looking for scenarios — and the scenarios are exactly what a reviewer checks for.
Every use error the process finds is a design change waiting to happen — before it reaches a patient.
Six Disciplines That Carry a Usability File.
From the use specification to the summative study designed to pass FDA’s human-factors review.
Use Specification & Context
Intended users, uses, and environments defined precisely — the foundation every later study is judged against, and the part teams write too loosely.
Use-Related Risk Analysis
The hazard-related use scenarios and critical tasks derived from the ISO 14971 file — the bridge between usability and the risk process.
Formative Study Design
Iterative formative evaluations that find use problems while the fix is cheap — the diagnostic work that keeps summative from becoming a redesign.
Summative Validation
The human-factors validation study designed to FDA’s expectations — representative users, realistic environments, and the critical-task scenarios that matter.
Usability Engineering File
The complete usability engineering file assembled the way a reviewer reads it — specification, analysis, evaluations, and conclusion, tied together.
Post-Launch & Change Discipline
Use-related evidence maintained as the interface changes — because a redesigned screen can reopen the very use errors the study closed.
FDA emphasises the summative study; the standard emphasises the process. The file has to answer both.
FDA and the Notified Body Read the Same Usability File Differently.
FDA’s human-factors guidance and IEC 62366-1 overlap heavily but are not identical — FDA leans hard on the summative study and its critical tasks, while the standard emphasises the whole process. A file built for one and shipped to the other often has a gap exactly where the second reviewer looks.
We build a single usability file that satisfies both, and connect it to 60601-1-6 where medical electrical equipment pulls usability in as a collateral — so one process serves the standard, the guidance, and the electrical file at once.
Six Failure Modes We Are Brought In to Prevent.
Most of them are a summative study asked to carry a process that never ran.
Summative with no formative
Jumping straight to the validation study — which then finds the use errors formative testing should have caught, at redesign cost.
A loose use specification
Intended users and environments defined vaguely — so the study can’t claim to represent them, and the file’s foundation is soft.
Critical tasks not identified
No clear link from use-related hazards to the critical tasks the summative study must cover — the gap FDA’s reviewers open first.
Unrepresentative participants
A study run with the wrong users or environment — and a validation that doesn’t validate what the label claims.
Usability divorced from risk
A 62366 process running beside ISO 14971 rather than from it — so the scenarios and the hazards never actually meet.
The redesign that reopened it
An interface changed after validation with no re-evaluation — reopening the very use errors the study had closed.
Human-Factors Leadership That Passes Both Reviewers.
Our leads have built usability files, designed summative studies to FDA expectations, and tied them to the risk process throughout.
“A use error is never the user’s fault in this discipline — it’s a design signal. 62366 is the process that catches it before a patient does.”
The discipline we bring to usability engineering.
Designing How People Use Your Device? Find the Use Errors Before They Find a Patient.
A senior human-factors lead can build the usability process from the use specification through a summative study designed to pass — not a validation asked to rescue a file.
Senior-led. Embedded in your team. No junior hand-offs.