Usability engineering is the structured process medical device manufacturers use to analyze, specify, design, and evaluate how people interact with a device, so that use errors are found and reduced before release. Standardized by IEC 62366-1, it treats the user interface as a safety concern and links it directly to risk management.
What is usability engineering?
Usability engineering, also called human factors engineering, is the discipline of designing a device’s user interface around the real abilities and limits of the people who use it: clinicians, caregivers, and patients. The user interface covers every point of contact, including displays, controls, alarms, connectors, packaging, and the instructions for use.
It sits inside design and development, running alongside design controls and risk management rather than after them. The core idea is straightforward. Many device failures are not component failures but use errors, and those errors are often foreseeable and can be designed out.
Why usability engineering matters in medical device development
Use error is a leading cause of medical device recalls and adverse events. A confusing infusion pump screen or an ambiguous connector can cause a dosing mistake regardless of how well the hardware performs. Regulators treat this as a safety issue, not a matter of convenience.
For manufacturers, the stakes are practical. FDA reviewers expect human factors evidence in many premarket submissions, and gaps can trigger deficiency letters that delay clearance. Under EU MDR 2017/745, the general safety and performance requirements call for reducing risks linked to use error and ergonomic design. Weak usability work also raises audit exposure and can force expensive redesigns late in a program, when changes cost the most.
How usability engineering works
IEC 62366-1 lays out a process that flows from understanding users to proving the design is safe in their hands. The main activities are:
- Use specification: define intended users, use environments, and the tasks the device supports.
- Hazard-related use scenarios: identify tasks where a use error could lead to harm, drawing on the risk analysis under ISO 14971.
- User interface specification and design: write requirements that address those risks, then design against them.
- Formative evaluation: test early prototypes with representative users to find and fix problems while change is cheap.
- Summative validation: a final study with representative users under realistic conditions, showing that critical tasks can be performed safely.
This process does not stand alone. It feeds and draws from risk management (ISO 14971), the quality system (ISO 13485, now referenced by the FDA QMSR), and, for electrical equipment, IEC 60601-1-6, which applies the same usability process to medical electrical devices. In the US, the FDA’s 2016 guidance “Applying Human Factors and Usability Engineering to Medical Devices” sets baseline expectations, and a 2026 final guidance on the content of human factors information in marketing submissions defines, on a risk basis, what to include in a 510(k), De Novo, or PMA.
Common challenges and best practices
The most common mistake is running a summative study too late, then discovering a design flaw that requires re-tooling. Teams treat human factors as a documentation exercise near the end rather than an input at the concept stage.
Another frequent gap is a weak link between the use-related risk analysis and the validation protocol. If critical tasks are not traced from hazards through to the summative study, reviewers push back. Good practice keeps that thread visible from start to finish.
Recruiting the wrong participants also undermines results. Studies need people who match the actual user profile, not convenient stand-ins. Instructions for use should be tested as part of the interface, since users often skip or misread them. Strong programs start early, run several formative rounds, and freeze the design before summative validation.
How SJML helps with usability engineering
SJML builds usability engineering into device design rather than bolting it on at the end. Its engineering teams run user-needs analysis and integrate IEC 62366 usability work with ISO 14971 risk management across mechanical, electronics, embedded, and software design. Formative and summative activities connect to the wider design controls and phase-gate program management SJML uses, with change control that keeps validation intact. In-house labs support related electrical safety, EMC, and reliability testing on the same program. For teams working toward FDA or EU MDR submissions, SJML aligns human factors evidence with the relevant quality system and regulatory pathway.
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Frequently asked questions
The terms are used interchangeably in medical devices. IEC 62366-1 uses “usability engineering,” while FDA guidance uses “human factors engineering.” Both describe the same goal: designing the user interface so that intended users can operate the device safely and effectively, and reducing use-related risk through structured analysis, design, and testing.
IEC 62366-1:2015, with Amendment 1:2020, is the core international standard. It defines the usability engineering process for analyzing, specifying, developing, and evaluating a device’s usability as it relates to safety. IEC 62366-2 is a supporting technical report with guidance, and IEC 60601-1-6 applies the same process to medical electrical equipment.
For many devices, yes. FDA expects human factors information in premarket submissions on a risk basis. The 2026 final guidance on human factors content in marketing submissions describes when a written rationale is enough and when full validation data is needed for a 510(k), De Novo, or PMA. Higher use-related risk means more evidence.
Formative evaluation happens during design, using early prototypes to find and fix usability problems while changes are inexpensive. Summative evaluation, also called usability validation, is the final study with representative users under realistic conditions. It provides objective evidence that intended users can complete critical tasks safely, and it supports regulatory submissions.
Related terms
- Human Factors Engineering
- Risk Management (ISO 14971)
- Design Controls
- IEC 62366-1
- Summative Usability Validation
