In capstone, I faced an issue where I was not sure how to test a component of the product. It is integrated that the enclosure I created did not have any leaks. So I looked up standards that could would be appropriate for my component and researched accordingly. I used a standard test regarding a gasket from the ASME. While the test they provided required expensive apparatuses and devices, I still proposed the idea to the customer who instead gave me a more simple test to perform. So an important factor to consider when creating test methods and protocols is creating based on the limitations and parameters you are in. It is important that the tests and protocols you create can actually be performed and creating one that requires a number of external devices that are not cost effective is not ideal. If there were no previous tests to refer back to, I would try to research scholar articles or different standards to garner similar tests or protocol and adjust/change them to fit the need at hand. 

Factors to consider when designing test methods usually pertain to the products application. Developing the test methods are a direct result of how your product will be used in the future as well as any scenario it might undergo. Take a knee implant for example, standard test protocols may involve wear resistance as well head on hits to the implant. However, there must be tests that involve forces being applied to all sides of the implant in the case of running into a corner or similar. Additionally, developing protocols to test the strength of the material after repeated use. The strength of an implant may vary from cycle 1 to cycle 1000 and so on.

@anthonynjit This is true. Developing protocols based on tensile strength of a device after repeated use is a commonly overlooked factor. I would have to believe its because big corporations might sign a contract with the buyer and cover the cost of repair if need be. That's why the overall strength and resilience of a product can be ignored or be less prioritized. Plus strength testing measures usually cost a lot of money and the manufacturing/product development team might not want to pay the exorbitant cost. 

Another factor to consider in verification activities is testing conditions that the actual product will undergo. This is not to be confused with validation however, which actually evaluates how the product is physically used. For the verification, you are testing certain outputs (ex. diameter measurement, strength, bio-absorbability time, etc) and the tests you develop should reflect the constraints that the product will have when used in the field with a safety factor. For example, if the the product is supposed to be absorbed in the body after 24 days, the test should evaluate in vivo conditions for more than 24 days, perhaps 40 days to evaluate the full effects. The team should evaluate to what extent a safety factor should be established for each test.

Another important aspect to consider when developing verification tests is your sample size. Say there are 100 pieces of a component per lot, and you need to verify the component can withstand a certain load. Load testing is destructive, so you cannot test every single component and still build product. Plus, it would be an inefficient use of time. Instead, the engineering team must use statistical reasoning to determine how many pieces out of the lot to test to be confident that the entire lot conforms to specifications. This can be done via a risk-based approach. If this component failing has a catastrophic, life-threatening impact on the patient, then the sample size is going to be greater to better guarantee it's going to work. Additionally, you can look at past trends for this component, or if it's a purchased component, the manufacturer's reliability. If the manufacturer has a history of producing bad parts, that is further reason to use a higher sample size.

First of all, the tests must comply with the regulations. If you do not manufacture a part of the product, and you have it done by another company, that company must comply with these regulations while performing the tests. Although you produce the product yourself, you may not have the required test device and you may outsource the testing service. In this case, the company performing the test should still comply with the regulations. Before the tests are carried out, the regulations should be examined, the necessary conditions should be checked and the test should be carried out in this direction. If possible, support should be obtained from companies that carry out the test procedures and no mistakes should be made.

I really like @srp98 's approach here. From the design specification document, you determine which specifications require testing. In @srp98's case, this was leakage from a gasketed joint. In @anthonyNJIT 's case, it was joint interface wear. The art here, in my opinion, is the search for an appropriate standard testing regimen that accurately investigates the specification you are looking for. I'm guessing here, but I would go with FDA referenced standards first, then perhaps ISO, and include relevant disciplines if neither of those gives satisfactory guidance.

This is an excellent discussion period some of the factors that I think would be considered when designing test methods have to do with relations to the product application. Understanding what the product will be used for in the future is very important to the test methods that will be used since they relate to one another. Verification activities are also to be considered for testing methods and protocols. It is important to have a good understanding of the manufacturer's reliability. Regardless what is a factor to being tested, it is significant to understand that the test must comply with the regulations that are put forth against different devices. There are a plethora of different factors but it is important to understand how many factors you can for a device so there are less problems in the future. Just obtaining as much knowledge as possible is great for rationalizing a test if there was no previous test methods to refer back to because then you are setting a precedent.

Designing verification tests is not something I have done from scratch, but I have some experience working in a lab and using these skills for tests. In a laboratory, many of the test methods are not made from scratch due to the complexity and time needed to create a new verification test. In the case of testing a raw material, for example, there are standards that are universally used, such as the United States Pharmacopeia, which outlaws test methods for certain materials. In testing a material, the USP would outline what the chemist can test for, such as purity, identification of the material, and chloride presence, among others. This became essentially helpful because, when you are worried about other problems, these test methods become useful in unfamiliar territory and can be transferred to other companies for testing these materials. Another verification test would be the pharmaceutical industry. In order to determine if water is not contaminated, measuring something as simple as electrochemistry would be useful. By conforming to the standard of water, we haven't invented a new definition but kept it simple. It is useful to many industries because it uses commonly used instruments. Complicating the water test would be to use something such as HPLC, but this would be too complicated for something that can be solved for hundreds of dollars compared to thousands. Designing a verification test should be simple enough that it can be run multiple times if needed, as well as being easily transferable to other fields of study.

Some of the design verification plans that is done for companies that manufacture medical devices are to see if that devices meet their design specifications and intended purpose. So this will be tests such as QC measuring using CMMs, optical comparators, optical gauging, material/strength testing, hipot testing, and many more. Thus, there are a lot of job opportunities that arise for these activities and we have learned some of these positions already which are Quality Assurance(people who make the tests) and Quality Control(people who execute theses tests).

Another major part of verification is the documentation and traceability of the production of these devices so these include keeping records of the different processes that goes into making the part, the measurements, and the material certifications for the product. Proper documentation is essential to demonstrate compliance with ISO 13485 requirements and this is why these are usually reviewed and thoroughly documented within a company. 

A factor to consider when developing a test method and protocol is repeatability. It is essential that the test can be performed at a different instance with a different operator. For example, in my current role, I do some mechanical testing using an Instron, which in some cases requires the development of a test method. In order for a test method to be completed, it requires a validation study that the results will be consistent from the test. Upon completing that validation, the next step would be to train other team members on that test method. In terms of developing a test, if there were not any previous similar test methods, it could be helpful to research other types of testing to see if there is an approach that could work for the method being developed. Additionally, this type of method would likely take a lot of trial and error in order to create the desired test. This approach of trial and error is something I have had to utilize when developing test methods as well as seeing if there are parts of other methods that I could incorporate into the method being developed. 

When developing test procedures and protocols, some important things to take into account could be Standards and Regulations Compliance aspects, which mean making sure our testing procedures adhere to relevant legal requirements.Additionally, the tests that are required should be determined by the medical device's intended usage and purpose.  The security of the patients and medical personnel using the equipment is an essential further factor. We  can do risk assessments and hazards tests. In situations where prior test methods are unavailable, we can work with experts in the field, such as scientists and engineers, to create new tests. In order to identify testing techniques used for similar devices or materials, we may also analyze relevant scientific literature and research publications.

When creating test methods and protocols, key factors include ensuring that the tests accurately simulate the device's real-world use, assessing risk to patient safety, regulatory compliance, and repeatability. Each test should align with critical design inputs, measure the appropriate performance criteria, and be reproducible across different setups and operators. If no previous test methods exist, statistics provide a solid framework to establish baseline requirements by analyzing similar devices or simulated conditions. In these cases, I’d rationalize a test by grounding it in clinical need, the design’s intended purpose, and user interactions. Statistical analysis would be crucial to developing valid test methods and protocols, as it ensures that the test results are reliable and represent the device's expected performance. Statistical tools can help determine sample sizes, confidence levels, and acceptable tolerances for measured values, all of which are key to minimizing errors. Additionally, using statistics to analyze test data allows teams to justify testing thresholds and acceptance criteria scientifically, ultimately improving test validity.