Usability for Medical Devices: A New International Standard

A recently published international standard requires manufacturers of medical devices to follow a systematic usability process. To comply, manufacturers of medical devices will need to change the way they design, develop, test and manufacture their systems.


Most companies know they cannot risk launching products with poor usability. They know that ultimately there will be a price to pay — expensive redesigns, poor customer experience, high volumes of customer service calls and complaints, lost user productivity and lost revenue.

But there are some industries in which the stakes are very much higher. For companies designing and manufacturing medical devices, poor usability is literally a matter of life or deathMore than a third of medical device incidents involve usability issues and, on average, 195,000 people die in American hospitals annually because of medical errors. While not all of those cases are attributable to specific user interface design problems, increasingly complex user interfaces are unquestionably a part of the problem.

Enter ISO/IEC 62366: Medical Devices – Application of Usability Engineering to Medical Devices. This is a new international standard aimed squarely at reducing the risk of medical errors due to poor interface design

ISO/IEC 62366 at a glance 

ISO/IEC 62366 is a process-based standard that aims to help manufacturers of medical devices ‘design in’ usability and 'design out’ usage errors. The standard also applies to documentation that may accompany a device, and to the training of intended users. However, it does not apply to clinical decision-making that may be related to the use of the device. The standard will replace ISO/IEC 60601-1-6: Medical electrical equipment - Part 1-6: General requirements for safety - Collateral standard: Usability. In doing so, ISO/IEC 62366 expands the scope to include all medical devices — not just electrical ones.

Manufacturers that follow the standard must adopt a user centered design process (called a Usability Engineering Process in the standard) that spans the design and development life cycle of the device. To comply, manufacturers must document the process in some detail in a Usability Engineering File.

The standard itself comprises just 6 pages. A further 80 pages present a number of detailed annexes along with useful worked examples — a veritable usability training course, in fact! — to help companies understand how to institutionalize the usability process and to guide them through the standard.

We still encounter development teams — across a range of industries, not just in the medical field — who are uncertain of what usability actually involves. For some companies usability still consists of little more than “checking a box”: medical companies in particular often assume that usability is accounted for by extensive pre-market clinical trials. Project teams are sometimes surprised to learn that you cannot “do usability” just by running a focus group, collecting customer opinions, tagging a few questions on the end of a market research survey, or simply conducting a test prior to launch. ISO/IEC 62366 corrects these misconceptions for manufacturers of medical devices in much the same way that ISO 13407 corrected the same misconceptions for other industries.

The Usability Engineering Process

The standard describes a Usability Engineering Process with 9 stages:

  1. Specify the application of the medical device. In this stage, you identify the most important characteristics relating to the use of the device (such as the intended medical indication, patient population, the intended user profile, conditions of use, the device’s operating principle etc.)
  2. Identify the device’s frequently used functions. Poor design and usability of frequently used functions — red routes — can seriously impact safety by increasing the probability of use errors. In this stage you identify these functions.
  3. Identify hazards and hazardous situations related to usability. In this stage, you catalogue characteristics of the device that could impact safety.
  4. Identify the device's primary operating functions. The primary functions are those functions that relate directly to the safety of the device and also include the frequently used functions identified earlier. The annex recommends functional analysis techniques that can be used in this stage. 
  5. Develop the usability specification. In this stage, you describe the user interface requirements for the primary operating functions, establish testable requirements for usability verification, describe use scenarios, and create testable usability goals. Note that the term "interface" applies to all parts of the device a user interacts with — not just to the visual display or touch screen, for example.
  6. Prepare the usability validation plan. In this stage, you create the test plan to show how you will evaluate the product. You describe how you will validate the usability of the device's primary operating functions and specify success criteria. You also define the test users and the test use scenarios.
  7. Design and implement the user interface. In this stage, you design the user interface.
  8. Verify the user interface design. In this stage, you validate the design against its usability specification and redesign as necessary. You can do this with an expert review or by testing with users.
  9. Validate the usability of the medical device. In the final stage, you test the device to ensure you’ve met the users’ goals. Your test needs to be carried out under actual or simulated conditions, usually before use on actual patients, though usability data can be supplemented by data collected during clinical trials. During validation you scrutinize the usability of all functions pertaining to the safe and efficient performance of the device. Validation needs to be carried out by people not directly involved in the design of the user interface.

Usability is an iterative process. If the acceptance criteria described in the usability validation plan are not met the process loops back to the user interface design stage. Note that the stages parallel those in ISO 14971: Medical devices - Application of risk management to medical devices. If you comply with the Usability Engineering Process, the residual risks associated with the usability of a medical device, as defined in ISO 14971, are presumed to be acceptable, unless there is objective evidence to the contrary.

The Usability Engineering File

To comply with the standard, you need to document all aspects of the process in a Usability Engineering File. This file provides traceability to demonstrate that you have followed the Usability Engineering Process.

The file can be part of the risk management file, or it may be part of the product design file, or it can be an independent document or set of documents. The file itself does not need to contain all of the records and other documents produced by the Usability Engineering Process, but it should contain references and pointers to the whereabouts of all required documentation. The file enables efficient auditing of the design and development process.

Taking steps to comply with the standard

In the USA, the Food and Drug Administration (FDA) has recognized ISO/IEC 62366 and has issued a list describing the documentation that must accompany any declaration of conformance to the standard. So here are three steps you can take now:

  • Start by obtaining a copy of the standard. You can buy the standard from ISO.
  • If you already comply with ISO/IEC 60601-1-6 you are most of the way there. You need to extend your Usability Engineering Process to include non-electrical devices and interfaces.
  • If you have an in-house usability team, they should become familiar with the requirements in the standard and should draw up a plan for putting the Usability Engineering Process in place. If you don't have an in-house usability team, you should find an experienced usability consultant who can help you understand the details of the standard and can work with you to implement the requirements. We recommend using a consultant that has prior usability experience in the medical industry because complying with the standard may require some radical changes to the way you design and develop medical devices.

Acknowledgements

Thanks to Ben Stokes and David Travis for comments on this article.

 

Philip Hodgson, March 2010