A use scenario (German: Nutzungsszenario, synonym: Benutzungsszenario) describes a coherent sequence of interactions between user, medical device, and use environment to achieve a specific use goal. Within IEC 62366-1, hazard-related use scenarios are described on the basis of identified hazards and hazardous situations and serve to plan and carry out further usability evaluations; the actual risk assessment takes place in the risk management process according to ISO 14971.
Function in the usability engineering process
Use scenarios form the bridge between the use specification, the use-related risk analysis, and evaluation. They turn abstract statements about user groups, context of use, and intended purpose (intended use) into traceable chains of action and thereby make visible relevant interactions that often remain hidden in pure function descriptions. Use scenarios also serve as the basis for deriving user tasks, test tasks, and evaluation scenarios.
Hazard-related use scenarios
IEC 62366-1 does not focus on arbitrary use scenarios but in particular on those with a potential safety relevance. A hazard-related use scenario describes a use situation that could lead to a hazardous situation or to harm. It can contain a potential use error but is not necessarily limited to one. Even correct use can lead to a hazardous situation because of inadequate characteristics of the user interface. Such scenarios are typically derived from risk management activities, known usability problems, vigilance data, and predecessor products, and they form the central basis for formative and summative safety evaluations.
Delimitation from user tasks, user stories, and use cases
Use scenarios are often confused with user tasks or user stories. A use scenario describes a complete chain of action within a context of use, whereas a user task is only a single activity or subtask within that scenario. User stories come from agile software development and describe requirements from the user's perspective. Use cases model interactions between actors and systems but have no regulatorily defined status in usability engineering for medical devices. The imprecise use of these terms often leads to inconsistencies in usability documentation in practice.
| Term | Describes |
|---|---|
| Use scenario | A complete chain of action within a context of use |
| User task | Only a single activity or subtask within that scenario |
| User story | Requirements from the user's perspective. Originates from agile software development |
| Use case | Models interactions between actors and systems. Has no regulatorily defined status in usability engineering for medical devices |
Derivation and documentation
Robust use scenarios are typically developed on the basis of context analyses, interviews, observations, task analysis, contextual inquiry, workflows, and risk considerations. Good use scenarios describe the user group, initial situation, use environment, product components used, relevant information, target state, and possible disruptions. Especially for home-use products, SaMD (software as a medical device) applications, and combinations of hardware and software, a precise scenario description is decisive for a valid risk assessment.
Use scenarios in formative and summative evaluations
In formative studies, use scenarios serve to make design problems visible early. For the summative evaluation, those hazard-related use scenarios are selected that, according to the manufacturer's selection procedure, are included in the evaluation. The FDA requires that the use scenarios considered in the summative evaluation (human factors validation testing) be described in a traceable way. The selection must be risk-based and justified. Not every product function necessarily has to be examined in a summative evaluation; what matters is its contribution to potential use-related risks.
Typical weaknesses in practice
A frequent mistake is to document use scenarios only as process flows or task lists. Further recurring weaknesses:
- Loss of important context factors such as time pressure, distractions, stress, or environmental conditions
- Consideration of normal operation only
- Neglect of exceptional conditions, unexpected events, and rare workflows
- Missing link to the description of user groups and context
Incomplete scenarios regularly result in relevant use errors being identified late or not at all.
Regulatory reference
IEC 62366-1 requires the identification and description of hazard-related use scenarios as part of the usability engineering process. They describe the safety-relevant use situations that are taken into account later for evaluation planning and the provision of evidence. As part of human factors validation testing, the FDA expects a description of the use scenarios used and of the critical and non-critical tasks they contain. The FDA approach is more strongly oriented toward critical tasks and the use-related risk analysis, whereas IEC 62366-1 defines hazard-related use scenarios as a separate process step. The MDR and IVDR (the EU regulations for medical devices and in vitro diagnostic medical devices) do not use the term "use scenario" explicitly but require the control and minimization of use-related risks and use errors. Use scenarios are an established means of demonstrating compliance with this requirement, typically through implementation according to IEC 62366-1.
Use scenarios translate abstract statements about users, context, and intended purpose (intended use) into concrete, testable chains of action. They are considered hazard-related if they could lead to a hazardous situation or to harm. Even a general use scenario can already contain safety-relevant interactions. Hazard-related scenarios support the selection and planning of formative and summative evaluations; the actual risk assessment remains part of the risk management process.
Frequently asked questions (FAQ)
Does every user task have to be assigned to its own use scenario?
No. A use scenario usually comprises several user tasks. The tasks represent individual action steps within a higher-level scenario.
Are use scenarios and use cases identical?
No. Use cases come from systems engineering and describe interactions between actors and systems. Use scenarios additionally take into account regulatorily relevant context factors, user characteristics, and potential use errors.
Do all use scenarios have to be tested in the summative evaluation?
No. The selection is risk-based. The focus is on hazard-related use scenarios, in particular those with relevant potential harms or risks.
Is a workflow diagram sufficient as a use scenario?
Usually not. Workflows show sequences but often do not capture environmental conditions, user characteristics, disruptions, uncertainties, or potential causes of error. For regulatory purposes, a more detailed scenario description is usually required.
Do you want to collect use scenarios for your medical device systematically and prioritize them on a risk basis? We support you throughout the usability engineering process according to IEC 62366-1.
More about our usability engineeringSources
- IEC 62366-1:2015+AMD1:2020, Medical devices, Part 1: Application of usability engineering to medical devices
- ISO 14971:2019, Medical devices, Application of risk management to medical devices
- Regulation (EU) 2017/745 on medical devices (MDR)
- Regulation (EU) 2017/746 on in vitro diagnostic medical devices (IVDR)