Definition of Terms

Originally Published MDDI April 2003

Design Control

User Needs: The subjective needs of potential users of the product in terms of their clinical conditions, living circumstances, context of product use, economic considerations, etc.

Requirements: The formalized and complete statement of the needs of all potential users of the product, as interpreted by the designers and verified by reviewing with a sampling of prospective users.

Specifications: A quantitative description of all of the features of a prospective product that would be necessary to meet the requirements. 

Implementation: The product itself plus all documentation describing the details of its components, methods of manufacture, instructions to users, etc. (essentially the items that comprise the device master record as required by the U.S. FDA).

Field Experience: All feedback from users that can be used to identify the successes and limitations of the product in meeting the users' needs, including items such as clinical reports, adverse events, returned goods, complaints, suggestions, etc.

Design Input: The starting point for the design, described in sufficient detail so as to permit a regulatory agency to evaluate the design output in terms of its responsiveness to the design input. We have defined the requirements plus guidance and constraints to constitute the input to our design process.

Design Output: The results of the design process. These are the product itself and all documents describing the design process, including specifications and implementation.

Verification: The process of comparing the output of each step of the design process with the input to that step in order to demonstrate that the results are consistent with the goals for that step. Thus, the specifications are compared against the requirements and the implementation output is compared with the specifications.

Validation: The process of demonstrating that the design process itself has met its goal of producing products that users are ready, willing, and able to use. 

Constraints and Guidance: The “facts of life” that must be considered in the design process:

• Clinical—Information about the disease process, its likely extent and progress in the patient population, and the lifestyles, capabilities, and limitations of patients and other users that might influence device use.
• Scientific—Information about the underlying physiological principles that govern the response of the body to a disease and potential therapeutic interventions, including limitations in the current state of knowledge that may need to be resolved in the process of developing and/or testing the product.
• Engineering—Information about the alternative technologies that might be employed, their features and limitations, and risk factors in their deployment.
• Regulatory—Information about the circumstances under which the device is likely to be field tested and the nature of the information that can be gathered.
• Business—Information about competing technologies, their clinical advantages and disadvantages; the “look and feel” of complementary product lines; the price-sensitivity of customers; and the sales, marketing, and training environment in which the product must gain clinical acceptance.

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