Scope of Application of Usability Engineering

Compliance with JIS T 62366-1：2022

Medical device manufacturers must ensure compliance with JIS T 62366-1：2022 “Medical devices – Part 1: Application of usability engineering to medical devices” (IEC 62366-1：2015 + AMD1：2020) for medical devices manufactured and marketed on or after April 1, 2024. Compliance with this standard demonstrates conformity to the requirements concerning usability stipulated in Articles 9 and 16, among others, of the Essential Principles for Medical Devices.

Manufacturers must implement usability engineering to design and develop medical devices free from use errors.

To achieve this, the following are required:

1. Establish a system to confirm conformity with usability-related requirements
2. Take necessary measures such as revising procedures to ensure compliance with IEC 62366-1
3. Explain conformity with IEC 62366-1 in the attachment materials to medical device approval applications and other submissions
4. During inspections, present documentation and provide appropriate explanations demonstrating that the design and development of the medical device was implemented in conformity with IEC 62366-1

What Is Usability?

In general terms, usability refers to the operability and ease of use of software and similar products. When a device can be operated in a straightforward manner without confusion or stress, it is said to have “good (high) usability.”

When designing user interfaces, it is necessary to appropriately consider the display and buttons while keeping usability in mind. Therefore, in usability engineering, risk management is implemented with focus on the user interface.

The user interface encompasses not only liquid crystal displays (LCDs) but also all elements recognized through human senses such as vision, hearing, and touch. Examples include instructions for use, labels, buttons, shape, color, and alarm sounds. Additionally, it is important to note that supplementary materials for medical devices (instructions for use, package inserts, educational materials, etc.) are also considered part of the user interface.

“Safe” Medical Devices without Use Errors

While usability encompasses “ease of use,” “user satisfaction,” and “appearance,” what is required in the design and development of medical devices is the creation of “safe” medical devices free from use errors.

Therefore, usability engineering as applied to medical devices is not a method for evaluating ease of use, but rather an analytical approach for designing safe medical devices without use errors.

For example, disposable lighters (100-yen lighters) have a heavy striking mechanism. This is a safety design to prevent children from playing with them and causing fires; the difficult operation is an intentional design feature for safety purposes. Similarly, in medical devices, when necessary for safety, the balance between ease of use and safety must be appropriately determined within the usability engineering process. Deliberately making a device harder to use for safety reasons is also a subject of usability engineering.

Scope of Application of Usability Engineering

All medical devices are subject to usability engineering.

It is important to note that the scope is not limited to ME devices (medical electrical equipment) alone. Class I devices are also not excluded. Regardless of the classification or function of the medical device, all medical devices with a user interface are subject to this requirement.

As mentioned previously, usability engineering applies not only to software interfaces but also to other types of interfaces (instructions for use, labels, buttons, shape, color, alarm sounds). Supplementary materials (instructions for use, package inserts, educational materials, etc.) are also considered part of the user interface.

Relationship with Risk Management

JIS T 62366-1：2022 cites JIS T 14971：2020 “Medical devices – Application of risk management to medical devices” (corresponding to ISO 14971：2019) as a normative reference. The usability engineering process is integrated within the medical device risk management process.

Specifically, usability engineering is implemented from the following perspectives:

• Identification of hazards and hazardous situations related to use errors
• Analysis of potential use errors
• Identification and evaluation of hazard-related use scenarios
• Establishment of user interface specifications
• Implementation of formative and summative evaluation

Through these steps, use-related risks are evaluated within the risk management process, and appropriate risk control measures are implemented to ensure safety.

Addressing UOUP (User-Oriented Use Phase with Unknown Design History)

JIS T 62366-1：2022 provides detailed specifications for addressing user interfaces with unknown design history (UOUP). For existing medical devices or legacy equipment, the complete development history or design intent may not be clearly documented. In such cases, the method described in Annex C of the standard must be used to retrospectively evaluate the existing user interface and confirm conformity with the usability engineering process.

In UOUP evaluation, formative and summative evaluations are performed on the existing user interface to demonstrate that use errors and safety-related hazards are appropriately managed.

Implementation Considerations

Medical device manufacturers must incorporate the above process into their internal quality management system and pay attention to the following points:

• Early integration of usability engineering into the design and development phase
• Definition of representative intended user profiles and clear specification of the use environment
• Identification of user interface characteristics related to safety
• Verification of the effectiveness of risk control measures
• Enhancement of conformity explanations in attachment materials of approval applications
• Evaluation of the impact on usability when design changes occur