Both IEC 62366-1 and the FDA Human Factors guidance emphasize the importance of identifying and analyzing user interactions to mitigate potential use errors. My recommended method for these starts with writing Use Scenarios.

A Use Scenario describes a specific situation or task where a medical device is used and highlights the user's goals, intentions and actions or more formally constitutes a “specific sequence of tasks performed by a specific user in a specific use environment and any resulting response of the medical device” (DIN EN 62366-1).

It thus serves as an instrument for identifying potential use errors or hazardous situations that, after having been properly analysed and mitigated, can drive our design into a safe, effective and user-friendly product.

Secondly, it serves as an excellent starting point for designing, planning and conducting your Summative Testing and Design Validation.

Thirdly, it can be used to directly elicit requirements and specifications that focus, not only safety and risk, but also user satisfaction, in short, designing an exceptional, brilliant product.

Fourth, writing Use Scenarios as a group helps align the development team around a shared vision. When everyone contributes to describing how the device will be used, hidden assumptions often surface. These can then be addressed early, ensuring a common understanding of the device’s use.

Fifth, discussing device usage early in a collaborative setting also helps establish a consistent language and shared glossary. This reduces the risk of future misunderstandings caused by different terms being used for the same concepts—an issue that often arises when teams work in silos.

However, writing strong Use Scenarios is sometimes easier said than done.

Here are my tips for writing better Use Scenarios:

Tip #1: Use a structure that satisfies both IEC 62366 and FDA

The backbone of your Use Scenario consists of a list of tasks. These tasks can then individually be analysed for use errors and connected to your Risk assessment. The association of the task and its resulting risk can then be used to categorize the Task is “critical” or not.

With this backbone in place, we shall also consider and include who (characteristics of the user), when (in which situation), why (for which goal), and where (use environment and environmental constraints) the Use Scenario is playing out. This adds necessary context for the next step – identifying risks.

Tip #2: Write Use Scenarios as a collaborative effort

Start with the most frequent Use Scenarios and deal with rare Use Scenarios (such as installation and decommissioning) later.

I strongly recommend working out the details of the Use Scenarios jointly, as a group. The reason for this is to eliminate the (tacit) assumptions your team members inevitably will make about the device.

Although group meetings might seem cumbersome at times, your development efficiency will vastly benefit from such activities, since they:

• Explicitly formulate the expected use to all member of the development team
• Give participants an opportunity to voice their understanding and concerns about the expected use, discuss these matters and finally converge as a group towards a single understanding of the device’s usage
• Harmonize the language and jargon used when talking about the device

I know it is tempting, but please resist the urge of letting an AI write the Use Scenario for you. You will then forgo the valuable benefits described above.

Tip #3: Apply an appropriate granularity

Strive to find an appropriate granularity when selecting which use scenarios and tasks to document. The granularity chosen should strike a balance between being fine enough to identify use errors that lead to serious risks but coarse enough to avoid the situation of an ever-changing use scenario, demanding updates for the smallest design modification.

Constantly having to update the Use Scenarios can lead to a state of change-fatigue and as a result, the Use Scenarios are “abandoned” by the team. A Use Scenario out-of-synch with the design can be even more dangerous that not having one at all. 

Tip #4: Analyse the Use Scenarios for risks

The next, and maybe most important step, is to analyse the tasks for potential use errors or misunderstanding. Connect these identified risk events to your existing risk assessment and expand it if necessary.

Note that analysing the risks for potential use errors is not only about mistakes done when performing the task. It is also important to analyse risks associated with not performing the task or performing the tasks in incorrect / unexpected order.

Tip #5: Update the Use Scenarios continuously

Use scenarios are living documents. Update them as your understanding of users, tasks, and risks evolves during formative evaluations or feedback from clinical studies.

In the end, the FDA expects that your validation study protocol draws directly from your Use Scenarios. The better and accurate your scenarios, the easier it is to justify that your validation tests are realistic and complete.

Strong Use Scenarios are the backbone of good usability engineering and a successful regulatory submission. By grounding your scenarios in real-world context, anchoring them to risk, and keeping them structured and current, you’ll meet the expectations of IEC 62366 and the FDA Human Factors guidance—and, more importantly, design safer, more effective devices.

Too often, scenarios are either too generic to be useful or so detailed they become unmanageable. And when they fail to reflect realistic use conditions, your usability engineering file—and ultimately your submission—can fall short.