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Manufacturers are compelled by regulations, commercial interests, standards, and ethics to ensure their medical devices do not induce use errors that could cause harm. Historically, use errors have led to a startling high number of adverse patient outcomes including death. In 1999 the Institute of Medicine estimated there are between 44,000 and 98,000 patient deaths per year due to medical error.1 Owing in large part to initiatives started over the past decade by the U.S. Food and Drug Administration (FDA) and standards bodies such as the Association for the Advancement of Medical Instrumentation (AAMI), the American National Standards Institute (ANSI), the International Electrotechnical Commission (IEC), and the International Organization for Standardization (ISO), usability testing has emerged as a principal means to identify user interface design flaws that could induce dangerous use errors. Usability testing has also become the conventional method of validating that design flaws have been effectively mitigated.
According to FDA, the need to validate a device's user interface applies to Class II (e.g., electronic wheelchairs, infusion pumps) and Class III (e.g., replacement heart valves, pacemakers)2 medical devices as well as combination products1, (e.g., transdermal patches and pen-injectors). Notably, FDA considers user documentation (e.g., user manual, quick reference card, hardware labeling) part of the user interface and therefore manufacturers should evaluate such items during summative usability testing. In the United States, the FDAs Center for Devices and Radiological Health (CDRH) and Center for Drug Evaluation and Research (CDER) both review summative usability test results in the course of their device evaluations. In Europe, the European Commission's Notified Bodies play the central review role.
Today, most manufacturers conduct a series of formative usability tests during the medical device development process to identify design strengths and shortcomings, and potential use errors. Manufacturers then make design changes to mitigate usability and safety issues identified during testing. The iterative process of designing and conducting formative tests is good preparation for a summative usability test, which serves to demonstrate that a production-equivalent device is ready for safe use on humans, presuming the test goes well.' The term summative usability testing is synonymous with validation usability testing. While formative testing is certainly a key step toward creating a safe and usable design, this article focuses on conducting a successful summative...