Design Control Guidance - Food and Drug Administration

e performed by device manufacturers. Rather, the manufacturer should select and applyappropriate verification techniques based on the generally accepted practices for thetechnologies employed in their products. Many of these practices are an integral part ofthe development process, and are routinely performed by developers. The objective ofdesign controls is to ensure adequate oversight by making verification activities explicitand measuring the thoroughness of their execution. Following are a few examples ofverification methods and activities.• Worst case analysis of an assembly to verify that components are derated properlyand not subject to overstress during handling and use.• Thermal analysis of an assembly to assure that internal or surface temperatures donot exceed specified limits.• Fault tree analysis of a process or design.• Failure modes and effects analysis.• Package integrity tests.• Biocompatibility testing of materials.• Bioburden testing of products to be sterilized.• Comparison of a design to a previous product having an established history ofsuccessful use.For some technologies, verification methods may be highly standardized. In other cases,the manufacturer may choose from a variety of applicable methods. In a few cases, themanufacturer must be creative in devising ways to verify a particular aspect of a design.Some manufacturers erroneously equate production testing with verification. Whereasverification testing establishes conformance of design output with design input, the aim ofproduction testing is to determine whether the unit under test has been correctlymanufactured. In other words, production testing is designed to efficiently screen outmanufacturing process errors and perhaps also to detect infant mortality failures.Typically, a small subset of functional and performance tests accomplish this objectivewith a high degree of accuracy. Therefore, production testing is rarely, if ever,comprehensive enough to verify the design. For example, a leakage test may be usedduring production to ensure that a hermetically-sealed enclosure was properly assembled.However, the leakage test may not be sensitive enough to detect long-term diffusion ofgas through the packaging material. Permeability of the packaging material is an intrinsicproperty of the material rather than an assembly issue, and would likely be verified using amore specialized test than is used during production.DOCUMENTATION OF VERIFICATION ACTIVITIES. Some verification methodsresult in a document by their nature. For example, a failure modes and effects analysisproduces a table listing each system component, its postulated failure modes, and theeffect of such failures on system operation.Section F. Design Verification 3/11/97 Page 31