Clause 5 of EN 62366, Usability Engineering Process, describes the steps in the process. As the standard points out in Clause 4.3.
Scaling of the usability engineering effort, they can vary in form and extent, depending on the nature of the medical device, its intended user and its intended use. In addition, the standard advises that, because of the iterative nature of the usability engineering process, the activities described in Clause 5 can be performed in any convenient order.
Briefly stated, however, the usability engineering process includes the following steps:
- Development of the medical device application specification, which identifies the most important characteristics related to the use of the device, based upon the intended medical indication, intended patient population, intended part of the body or type of tissue with which the device interacts, intended user profile, intended conditions of use and operating principles. The application specification lays the foundation for defining the usability specification.
- Determination of frequently used functions that involve user interaction with the medical device. This is an important step in the process because inadequate usability of frequently used functions can adversely affect safety by increasing the probability of use error.
- An identification of hazards and hazardous situations related to usability, which includes the identification of characteristics related to safety and of known or foreseeable hazards and hazardous situations. These activities are part of risk analysis and are to be conducted according to EN ISO 14971.
- Determination of the primary operating functions with input from frequently used and medical device safety functions.
- Development of the usability specification, which will provide testable requirements for usability verification, and testable requirements for usability of the primary operating functions, including criteria for determining the adequacy of risk control achieved by the usability engineering process.
- Preparation and maintenance of the usability validation plan, which specifies the methods and success criteria for the validation of the usability of primary operating functions and specifies the involvement of representative intended users; it must also address frequent-use scenarios and reasonably foreseeable worst-case use scenarios.
- Design and implementation of the user interface as described in the usability specification employing, as appropriate, usability engineering methods and techniques.
- Verification of the medical device user interface design against the requirements of the usability specification.
- Validation of the usability of the medical device according to the usability validation plan.
The results of the usability engineering process should be recorded in the usability engineering file; however, if the records and documents are part of other documents and files, the usability engineering file can refer to the location of these records and documents.
In many cases, the most efficient and cost-effective method of obtaining usability data is to collect these data during a premarket clinical investigation that is being conducted to establish safety and performance as part of device validation. This approach has the advantage of reducing the number of studies needed and also avoiding potential problems in determining ethical and regulatory requirements applicable to the usability aspects of the study.