Human Centered Strategies

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Human Factors in the Design Controls Process

The Quality System Regulation's Design Controls (CFR 820.30) is the FDA's accepted process for device design and is shown in the figure below. Human Factors activities are essential at each stage for identifying use error risks. (Click on an activity for more detail).

For more specfics on Human Centered Strategies services and deliverables regarding this process, see our Products page.

Early Team Inputs -- Inputs from users should come as early in the design process as feasible. A variety of techniques can be used including one-on-one Contextual Inquiry or group processes that are aimed specifically at understanding the tasks of the user. The results must be task-focused, however, and allow their clinical objectives to be voiced in terms of the device concept and how it will solve their problems or deliver care. [back to process]

User Profiles & Use Scenarios -- User Profiles and Use Scanerios form the foundation for understanding the critical elements of use error risk. User Profiles are descriptions of the key parameters of segments of the anticipated user population. Age, gender, physical and mental limitations, training and knowledge, and experience are several of the aspects that define different populations of users as determined by intended use of the device. Use Scenarios are narratives of how the user interacts with the device under different circumstances, environments, and intentions. The User Profiles and Use Scenarios form the basis for Task Analysis and Use Error Analysis. Interviews with expert users and representatives of the user population are helpful in gathering inputs for User Profiles and Use Scenarios.

Task and Use Error Analysis -- Task and Use Error Analyses performed with early device concepts are a vital part of establishing the process of understanding and controlling the risks of use error with your device and should be a part of the overall Hazard and Risk Analysis contained in the Design History File. Methods may include graphic representations of the user task flow of interactions with the device but they should include an identification of anticipated, observed, or predicted errors, mistakes, and omissions on the part of the user at each step. Additionally, the risk of each use error should be assessd in terms of potential harm to the user or patient. Mitigation strategies for use errors should be suggested at this point, although design solutions may not emerge until a more full design concept is built. [back to process]

Formative Usability Testing -- Formative Tests of your device are one of the most powerful tools you can use to detect the risk of potential use errors with your device concept. Cost effectiveness is a major attribute, because you can conduct these highly informative sessions with only 8-10 users and discover as much as 90-95 percent of use errors that are likely to occur with your present design. They should be conducted one-on-one, with early "working concepts" or simulations as the design cycle will allow. They should be "task oriented", allowing the user to perform specific tasks with the device while talking about issues they see in the interaction. [back to process]

Human Factors Design Standards -- During the Design Input and Design Verification phases of device design, Human Factors Design Standards are used to guide the design team on basic and specific user interface design principles that lead to improved usability and reduced chance of use errors. AAMI, ISO, and IEC standards, covering both the overall human factors process and specific hardward and software interfaces. These standards have been adopted by the FDA as representing best practice. for a complete list of human factors standards and how to obtain them, refer to the FDA's CDRH Human Factors website on this topic. [back to process]

Usability Test Plans -- As the device design becomes firmer, a series of formative and summative usability tests should be planned to check the validity of your use error mitigation plan and identify aspects of the design that still may produce use errors. Usability test plans are detailed protocols of evaluations with eventual users and become part of the overall Design History File (DHF) for the device. Protocols include the number and type of participants, the scenario of use and tasks to be tested, usability criteria (if appropriate), the testing setting and required equipment, measures of user performance (accuracy, time to complete tasks), and planned data analysis.

protocols

Usability Test Plan

Summative Testing -- The use of formal summative tests to validate the user interface and user documentation and labeling material against usability specification criteria (rates of success on various tasks) is essential in providing evidence will be able to interact effectively with all aspects of the device. Such tests should be carried out with near production-level versions of the device and conducted in simulated or actual environments of use. Caution should be exercised in employing summative studies as a part of the overall use error risk investigation. Failure cases and use error instances, especially on tasks with severe safety implications, should be identified and analyzed along with plans for mitigation of these failures.

Use Error Mitigation and Control -- There are several methods for mitigating and controlling identified use errors. The FDA offers a preferred heirarchy of these methods based on their history of effectivity on reducing adverse events.