Creating a usability file is a crucial part of the product development process for medical devices, including Software as a Medical Device (SaMD), in order to ensure user-centred design and safety. IEC 62366-1 is the international standard that outlines the process for applying usability testing to medical devices. It provides a structured approach to ensure that devices are designed with the user in mind and that potential risks associated with their use are identified and mitigated.
In this blog post, we’ll explore the key steps and components involved in creating a Usability File according to IEC 62366-1…
What is IEC 62366-1?
IEC 62366-1 is a standard that defines the usability testing process for medical devices. The standard emphasises the importance of understanding user needs, tasks and environments in order to minimise the risks associated with user errors and to improve the effectiveness of medical devices.
A usability file is a documented record of the usability engineering process made throughout the lifecycle of the device. It’s important for showing compliance with regulatory requirements and ensuring the safety and effectiveness of the device from a user’s perspective.
Key Steps in writing a usability file
What goes into a usability file? How do I make sure all the requirements in the standard are met? What do I need to do? These are all common questions many people have when starting to write their usability files, but don’t worry, we’ve broken it down for you!
- Define the Scope of your usability file
This includes the specific user population, the intended use, and the context in which the device will be used.
- Intended users: who will use the device? This could include healthcare professionals, patients, caregivers, or other stakeholders.
- Intended Use: What is the device meant to do? This includes the specific tasks it is designed for, such as monitoring, diagnosing, or therapeutic use.
- Use Environment: Where will the device be used? The environment can significantly impact the usability of the device (e.g., home use vs. hospital setting).
Tip: In your file, include a clear description of these aspects – these are more often encompassed in one ‘use specification document’. This forms the foundation for your usability engineering process.
- Conduct a Risk Analysis and identify use-related hazards
IEC 62366-1 requires that you conduct a thorough risk analysis to identify potential use-related hazards. These are situations where the user could make an error, leading to harm or malfunction of the device:
- Hazard Identification: identify potential hazards that could arise from user errors or inadequate design. For example, can a patient misinterpret a warning or misuse a medical app?
- Risk Assessment: Evaluate the likelihood and severity of harm associated with each hazard. Includes analysing whether a particular user action could result in patient harm, incorrect diagnosis, or delayed treatment.
Tip: Document each identified hazard and its associated risk. This is typically done in a hazard analysis table. The methods used to mitigate each risk should also be defined.
- Define user Interface (UI) Design Requirements
Based on the user needs and risk analysis, the next step is to define UI Design requirements that align with the intended user population.
- Human factors: Consider cognitive, physical, and sensory capabilities of your intended users. For example, if the device is intended for elderly patients, make sure fonts are large, and the interface is simple and easy to understand.
- Design Specifications: These should include clarity in labelling, controls, alarms and any instructions for use (IFU). You may need to adapt these for specific groups like non-professional users or those with visual impairments.
- Task Flow: Design the UI in a way that minimises the chance of error. For example, critical tasks should be easy to access and perform without unnecessary steps.
Tip: In the usability file, include UI specifications and design rationales explaining how the interface is designed to minimise errors and improve usability.
- Formative Evaluations
These are an essential part of the usability engineering process. This involves testing early prototypes or design concepts with users to identify potential problems before the final design is completed. These are repeated until the major risks are mitigated.
- User Testing: Conduct usability tests with representative users to evaluate the device’s interface and interaction design. This can include cognitive walkthroughs, task analysis, and heuristic evaluations.
- Iterative Testing: based on feedback from use simulations, iterations on the design are made to address any issues found during testing. This can involve revising the UI, adjusting instructions, or simplifying tasks.
Tip: Document test plans, test protocols and results of formative evaluations. Include the user feedback and any design changes made as a result.
- Summative Evaluation (Final Testing)
Summative evaluation focuses on validating the final design to ensure that the device meets the usability goals and performs safely and effectively in real-world scenarios.
- Final Usability Testing: Conduct usability testing on the final device to confirm that it performs as expected and that users can operate it safely. This often involves more realistic use scenarios and may be done in a clinical or home setting.
- Task Performance Metrics: assess whether users can successfully complete key tasks, such as using the device without errors, interpreting information correctly, and following safety instructions.
Tip: It’s best to include a detailed summary of the summative evaluation results, including task completion rates, time on task, error rates, and any corrective actions taken based on the results.
- Post-Market Surveillance and Usability Monitoring
After the product has been released to the market, continuous monitoring of usability is important. Post-market surveillance can help identify emerging issues or areas for improvement.
- Incident Reporting: establish a system for collecting feedback and reports on user-related issues. This needs to include complaints, adverse events, or usability failures.
- Usability Improvements: if usability issues are identified post-market, these should be addressed through iterative improvements or design updates.
Tip: Include a plan for post-market usability monitoring in your usability file. This could include plans on how to collect feedback and how to analyse and address the issues after the device is launched.
- Compile the Usability File
The final usability file should provide a comprehensive record of the entire usability engineering process, from risk analysis and design specifications to testing and post-market surveillance. The file should demonstrate that you’ve followed the usability process outlined in IEC 62366-1 and that all necessary steps have been taken to ensure the device is safe and effective.
Tip: The usability file should be organised into sections that clearly document each stage of the process. Include:
- Scope and intended use of device
- Hazard analysis and risk assessment
- Design specifications and user interface guidelines
- Formative and summative test results
- Post-market usability monitoring plan
But what about those devices that were placed on the market before IEC 62366-1:2015? How can they be compliant with the requirements?
Well, good news! IEC 62366-1 has a clause specifically for this scenario. The clause is called ‘User Interface of Unknown Provenance (UOUP)’.
So, after all, writing a usability file according to IEC 62366-1 is a critical step in ensuring the safety, effectiveness and user-friendliness of your medical device or SaMD. By following a structured usability engineering process – from defining user needs and conducting risk analyses to iterative testing and post-market surveillance – you’ll be able to create a comprehensive file that not only meets regulatory requirements but also ensures a positive user experience.
It’s important to keep in mind that usability is an ongoing process. Regular testing, feedback, and updates are essential to maintaining the safety and usability of the device throughout its lifecycle. A well-maintained usability file will provide essential evidence for regulatory submissions, product safety and continuous improvement.
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