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HUMAN FACTORS

Sensys Medical’s development of a noninvasive glucose monitor demonstrates the integration of human factors analysis throughout the design and development process. Linda Hockersmith, Sensys’s vice president of clinical operations and regulatory affairs, explains, “Our regulatory consultant recommended intensive human factors activities to maximize the design of our glucose monitor and support its home-use application.” The company’s first step was to review guidance documents, such as the AAMI standard on human factors in design processes. Based on advice from the consultant, Sensys also began developing planning documents during the product’s initial phase. The planning phase usually includes outlining steps for validation and risk management. Sensys also sought help from outside human-factors specialists, who prepared a comprehensive plan to define the scope of integrating human factors activities into the design project. According to Hockersmith, the plan detailed coordinating internal and external functions involved in the process, including an outside manufacturer. Hockersmith explains that the plan was necessary, not only to understand the activities, but also to understand timing.

During the requirements specification phase, Sensys conducted user research to understand and define the prospective users of the device and the environments of use, parameters that were critical to the accuracy of the user-interface document. An in-house clinical study enabled Sensys scientists and engineers to work with prospective users of the device on a daily basis. A task analysis defined, step-by-step, how users would interact with the device and the cognitive and behavioral requirements the device needed to satisfy. In addition, the task analysis provided performance metrics for further formative and summative studies leading to verification and validation.

Sensys then scheduled a series of usability tests. Often, the best time for such tests is while the product is being designed and built. Sensys experts devised job aids, something like operations manuals, from the task analysis. The tests helped the company identify some problems with the user interface that were quickly remedied.

Future tests include a formative, preclinical field study in which users will be observed and given questionnaires about interacting with the device. This study will be conducted in two parts. The first part will evaluate the company’s training program and how well that program is applied by the user. The second part will evaluate ease of use and correction of device use error. Following that, a pilot study will observe users operating the device during training and in actual home environments without the company interacting with users. A pivotal study, says Hockersmith, will be market testing, which will serve as the actual validation of the entire human factors effort.

Rigorous human factors testing is essential to give the device a chance for success. Sensys designed the glucose monitor to have some self-correcting mechanisms to reduce use error. In addition, the firm wanted the device to reduce error messages and to limit the number of times users have to retest. Less than 10% of glucose tests should result in an error, and these should be easily corrected so that users do not have to repeat the test more than once. “Many glucose-monitoring tests end with error messages such as ‘not enough blood acquired,’” says Hockersmith. “The pilot and pivotal home-use studies involve device tracking of all measurement attempts and subject questionnaires in which users who receive an error message answer questions about their actions prior to the failure and provide subjective information about their experience in correcting the error.”

Because of the comprehensive human factors analysis from the very beginning of design and development, Hockersmith expects the device to be very successful. By integrating human factors analysis early, the company established an approach that designs and tests iteratively, producing critical feedback to the designers at each stage.

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