What is Verification and Validation
Design Verification and validation are essential concepts for the design process of a medical device and it is of fundamental importance to fully understand the differences and the requirements associated with these activities. In this post we provide an overview of the FDA requirements for design verification and validation
Verification and Validation: some definitions
Firstly, let’s start with some definitions. The definition of Design Verification and Design Validation is reported in section 820.30 of Code of Federal Regulation (CFR), at the lefters f) and g). Specifically:
- Design Verification is confirmation by objective evidence that design output meets design input.
- Design Validation means establishing by objective evidence that specifications (specified requirements) conform with user needs and intended use(s).
Design validation means performing specific tests on the device to demonstrate it works for end user according to its specific intended use. If for example we imagine to have a product which is only constitute by software (the so-called, SAMD, Software as Medical Device), design validation means demonstration that we call Global System Requirements (that include user needs) are fulfilled.
If, instead we take in consideration a general hardware device, Design Validation shall include, a part fulfilment of the identified user needs, testing activities related to the safety of the device according to its intended use, for example:
- Biocompatibility Evaluation
- Electrical Safety and Electromagnetic Compatibility
- Packaging Validation / Sterilization Validation
It is essential to have a traceability between user needs/ system requirements and validation tests used to demonstrate fulfilment of that specific requirements. For example:
|User Needs||Validation Test|
|The device shall be safe to be used |
on patients from biocompatibility
point of view
|Validation activities related|
to compliance with ISO 10993
family of standard.
Design verification as per FDA requirements
Within the design process, design verification, as mentioned before in the section related to the definition, means demonstrating that the design outputs match the design inputs. From practical point of view, it means to identify specific requirements that could be related to functionality, performance, usability and safety of the device.
For each of this specific requirements a test plan and report shall be documented to ensure that each of the identified requirements is met.
Design verification is not focused at a system level, as per design validation; but rather it can include testing activities on all the layers of the design process. For instance, considering the scheme mentioned in the section before, for a SAMD, design verification includes code review, unitary tests and system verification tests.
Verification vs Validation
If we want to compare the characteristics of verification vs validation activities, let’s have a look to the table below:
|Scope: Design Outputs |
meet Design Inputs
|Design meets user needs and |
intended us of the device
|System, subsystem and |
|Test focused at a system level|
|During development.||After Development|
|Can be performed on |
|Shall be performed on the |
same devices as the ones
that will go on the market, or
|It is performed against |
selected by owner of the
|It is performed agains |
the selected user needs and
by international standards.
Specific FDA Requirements for Design Verification and Design Validation Activities
There are specific requirements that are needed to be fulfilled for verification and validation activities. Specifically, both for validation and verification, test plan shall include methods, acceptance criteria, and, very important, statistical techniques with rationale for sample size. For the latter point, it is extremely important that the sample size used for verification and validation tests is justified from statistical point of view to ensure that the number of samples tested is signification from statistical stand point.
Furthermore, for design validation there is another important requirement related to sample type. In fact, as mentioned before, the ISO 13485:2016 reports:
Design validation shall be conducted on representative product. Representative product includes initial production units, batches or their equivalents. The rationale for the choice of product used for validation shall be recorded.
FDA requirements for design validation are very similar to the one reported above.
It is very clear that the validation activities shall be performed on final devices and that a justification for sample type used for validation activities shall be documented. It is important to mention that this applies to all the validation activities, including clinical validation.