The verification method is one of the three essential elements required for performing a design verification process. If you have a medical device, you will need to go through this process. However, you cannot simply select the verification method, you need to derive it by going through the following two steps: drafting (review the requirements and the concept design to outline the method) and checking (review and update the method to ensure its adequateness). Once developed, you have to regularly review it throughout the design process.
Step I. Draft the verification method
The specific details of the verification method can be produced by either reviewing the device design or simply going over the requirements and drawing on the experience of previous similar designs. For innovative designs, you can either use available documentation for previously marketed medical devices or put in charge experts who have the experience and knowledge to develop it. However, whether you are developing a novel or more standardised verification method, the following 5 sub-steps should be followed:
- Use standards and guidance documents:
- You can find these types of documents through bodies, such as BSI (British Standards Institution) and IEC (International Electrotechnical Commission).
- Reviewing standards and guidance documents can provide you with various types of information (e.g. criteria for acceptability and references to other potentially relevant standards) that you can later use to formulate your verification method.
- If the verification methods found in the content of standards and guidance documents are relevant but not applicable directly, you can combine or modify them so that they fit your device design. Sometimes, you may find a directly-relevant method but you may need to adapt it a bit to make it compatible with the specific form of your medical device. If you cannot find any relevant methods, investigate similar devices and the methods used for their verification process.
- Use documentation from previously marketed devices – this type of documentation can be a useful source of information regarding recognized verification methods and procedures for verification activities. Finding such information and using it can help you save considerable time and effort in following the verification approach, as well as help you present a solid case for regulatory approval.
- Use expert opinion and scientific literature – the experience and knowledge of external experts (e.g. medical associations, conformity assessment bodies, industry experts, and regulatory expert review panels) can help you determine the most appropriate verification method for your design verification process.
- Use performance risk analysis – this analysis plays a critical role in determining the focus of any verification action because it shows you how a medical device can fail (i.e. its failure modes) and what should be verified. Once you have identified the failure modes, you can start the verification to demonstrate the correct performance of your medical device. In this regard, the device performance can be influenced by in-use conditions (e.g. users and environment), so keep in mind that when developing a verification method intended to simulate in-use conditions, you need to be wary of ‘method creep’. The latter usually occurs when, for some practical reasons, the quality of the method is reduced until the method is no longer a reasonable representation of the in-use situation. To guard yourself against it, don’t miss to perform step II ‘Check the verification method’.
- Use both empirical and analytical techniques – the use of a combination of both techniques in the verification of the design can help you maximise the chance of discovering potential device problems.
Step II. Check the verification method
After drafting a verification method, you should review it to ensure it is likely to produce the intended quality of results. The review is very thorough for more critical verification activities and in cases when there is a significant degree of uncertainty in the quality of the selected verification approach. A high degree of uncertainty occurs when a novel method has been derived. Therefore, to make sure the review is performed correctly and you have a reliable verification method in hand, you should use the help of experts such as clinical specialists, the device’s designer, test engineers, conformity assessment bodies, etc. For the review of the verification method, it can be used VFMEA (Verification Failure Mode and Effects Analysis) as it investigates how the verification elements could produce inaccurate results and what the effects of such failures might be.
To conclude this post, keep in mind that the regulatory authorities would expect you to use a standardized method. Such methods have already been tried and tested, and they can usually provide you with an adequate degree of assurance and meaningful results. However, if you decide to employ a non-standardized method, you need to remember that the costs on the project may increase significantly. The reason for this is that you will need to use additional resources to derive the method and validate the results, as mentioned earlier in step I. Non-standardised methods are often used for design verification of innovative medical devices.