Medical Devices: How To Set Out A Good Design Verification Approach

Setting out a proper and effective verification approach is not uncommon for a medical device manufacturer, and it is especially true when specialists (e.g. clinical experts, conformity assessment bodies, etc.) are involved. However, during the process of developing such a strategy, various problems may arise. For example:

• Some factors, such as commercial and development risks, are not fully accounted;

• There is overlooking or disregarding concerning the planning and execution of some key verification activities.

To overcome these and other problems, the below method can be used. It represents a ‘route map’ which, if followed, can help ensure that the verification timing and quality are appropriate from a regulatory and commercial standpoint. The proposed method consists of three stages which may need to be repeated more than once during the design verification process.

Stage I. Outline a verification plan

The focus of this stage is on performing an analysis of the requirements in order to assess when a verification activity is required during the product design process. The verification plan describes when each one of the protocols should be executed and relates closely to the project plan depending on the medical device manufacturer’s documentation practices. As can be seen in the figure above, this stage is divided into the following three steps:

              Step 1. Performing a review of the requirements and then drafting protocols where candidate verification methods are identified and required resources specified - Each protocol should contain as many of the following details as possible: verification requirement, the scope of the verification, acceptability criteria, characteristics of the model, verification method and references to standard methods, and required resources.

              Step 2. Assessing product development risk - it helps determine the importance of the various design and verification efforts. This step can be divided into four sub-steps, as follows:

• Assessment of the effects of not fulfiling each requirement – these effects must be assessed in terms of their impact during the device development and their commercial impact by bearing in mind how risks propagate. The Functional Analysis System Technique (FAST) is a good approach for performing such an assessment.
• Determining which requirements are likely to be most difficult to meet - the likelihood of failure and uncertainty should be considered.
• Assessing the risks of failing to meet each one of the requirements – development and commercial risks should be considered as they may have an equal part to play in dictating any resulting redesign or verification priorities. Moreover, a graphical illustration of each risk should be created for clarity reasons.
• Determining design and verification priorities – the schedule may be influenced by, for example, the resource accessibility and the dependance of some parts of the medical device design on the design and verification of others.

              Step 3. Final drafting of the verification plan – once outlined, it will help with resource scheduling and provide early visibility of the scope of the required verification activities.

Stage II. Improve the verification plan

The beginning of this stage is immediately after the design concept has been selected. Its main goal is to determine whether redesign or verification is needed at any point in the medical device design process. This stage helps improve the quality of the verification plan by providing detailed information about the methods for regular and final verification activities and determining their timing in the design process. This stage requires the performance of design analysis and can be divided into five steps, as follows:

              Step 1. Determining the verification demand – this step aims at establishing how urgently verification is needed and how much the identified risks need to be reduced. To determine the demand, it is imperative to do a re-assessment of the verification priorities. Therefore, the requirements review should be re-done while, in the meantime, considering all types of risk. Once this is done, it should be possible to be decided whether a redesign is necessary or verification. If re-design is needed, then stage II has to be repeated once the re-design has been completed. However, if verification is required, then its urgency and the need for uncertainty reduction have to be determined.

              Step 2. Reviewing the candidate verification methods

              Step 3. Assessing the benefits and limitations (e.g. costs and practicality issues) of each method to determine each one’s ability to reduce risks – this step focuses on ensuring that the selected verification method is sufficiently sensitive, accurate and capable of producing reliable results.

              Step 4. Selecting a preferred verification approach – the selection should be based on the demand for verification and the pros/cons of each candidate method. It can be easily done by using a table to compare the benefits with the costs and the benefits with the need for uncertainty reduction. Then all methods that are inadequate or too costly should be eliminated and the rest of them reconsidered and compared with one another. Once an appropriate method has been selected for each requirement, the information about each method should be entered into a verification protocol. Lastly, the verification plan has to be updated with the info on the selected plan.

              Step 5. Where necessary, validating the selected methods – the validation is done only in cases when the accuracy of the results is still questionable and has to be assured. Its need can be determined by, for example:

• Assessing the novelty of and the level of confidence in each method;
• Assessing the consequences of a misleading result.

One way of validating a method is to execute it and then collect and compare the results with ‘known’ results produced by an already recognized method. Another way is to perform the validation in stages by breaking down the method into its constituent parts.

Stage III. Execute all protocols

This is the moment when all protocols need to be checked before being executed. This stage consists of the following two steps:

              Step 1. Completing the protocols – the procedures to be followed must be absolutely clear, finalised and approved before proceeding with the protocols’ execution. A good practice is to have a complete list of all the protocols with their intended order of execution.

              Step 2. Executing the protocols – the execution of the verification protocols is according to the schedule in the project plan, and it occurs right after the verification approach has been determined. Then, the produced results have to be documented and any deviations from the predicted outcomes noted and justified. In the end, the results should be compared with the acceptability criteria and any follow-up procedures noted.