What Should You Do When a Testing Standard Doesn’t Exist? Part 3: Develop and Validate your own Test Method

In part two of this series, we talked about working together with the standard organizations to develop a new test method. In this part, we’ll discuss another option to consider when a testing standard doesn’t exist: develop and validate your own test method and obtain FDA approval.Image

Test method validation is the documented process of ensuring that a test method is appropriate for its intended use. It is essential that a test method produce reliable results so that product quality and safety can be assured.

The rigor of the test method validation should be dependent upon the risk associated with the use of the test method. Risk is the combination of the probability of harm and the severity of harm. A high level of rigor in the test method validation results in a higher level of validation credibility, thus reducing the risk associated with the use of the test method.

Test method validation is recommended when a new method is developed or an established method is revised. It can also be a useful tool to compare methods used for the same purpose.

Validating your own test method can be a quicker process than working through a standards organization. One disadvantage to this process is that you will be working without external input from industrial peers. Additionally, once the FDA deems your test method unacceptable, continuing to work with the FDA to gain their approval can be an expensive and time consuming process.

In the next part of this series, we’ll look at more options to consider when a testing standard doesn’t exist.

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4 common medical device testing questions and how to find balance from an engineering perspective.


Being an engineer in the medical device profession for the past 15 years has been quite an education.  Working with a team of talented engineers has been fun and together we’ve been able to learn from each other and solve almost any problem from an engineering perspective.  Our team has worked on several first to market Class II and Class III medical devices from the ground up, these experiences have been very helpful for us in transitioning from a large medical device company to a consulting firm.  As anyone who has worked in this field knows, sometimes you learn the most when your device fails, but it is what you do after your device fails that defines your career.  To sum up in a few words, what we’re really trying to do as medical device engineers is  find balance between risk and benefit.  Engineers write standards, guidance documents, papers and books to communicate how to find the right risk balance. Even with appropriate references in place, we have several questions that come up during most device development lifecycles.

1. When do you justify and when do you test?

You can have the perfect scientific justification to not test a device, yet the 1000 words that it will take to justify often become more expensive than a simple test. Tests have their own associated risks and costs.  How do you find the balance?

2. How do you choose the right confidence and coverage for a potential failure mode?

Often times test plans are developed with 90% confidence that 90% of the population will not encounter a failure mode. How does one know that this confidence interval is good enough for patient safety? This is a tough question that when put into a FMEA procedure can become systematic.  I’m not sure this should be a systematic question when a potential failure mode is death. How do you find the balance?

3. When is the worst case model a bad enough case?

The terms worst case conditions or worst case model often come up during device development.  What is the worst case scenario and will my device survive when this scenario happens?  And if you design your device for the worst case, what happens to the rest of the population?  Questions like this are hard to answer and can slow product development to a halt. How do you find the balance?

4. How close to the acceptance criteria are too close?

What if your safety factor is right on top of the acceptance criteria?  How does one justify questions like this?  Is there uncertainty analysis incorporated and what was that acceptance criteria based upon anyway?  When pushing the limits of device design to treat a new disease, questions like this arise. How do you find the balance?

Moving a medical device from concept to clinical use is a rewarding accomplishment.  There is quite a grind along the way and many tough questions to answer.  Finding your way through these questions is difficult, but when you get it right, patients benefit.  When you do find the right balance, everyone wins!

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What Should You Do When a Testing Standard Doesn’t Exist? Part 2: Working through Standards Organizations

In part one of this series, we discussed how medical device technology can frequently outpace the development of standardized testing methods. One potential solution to this dilemma is to work with the standard organizations to modify an existing standardized method or to publish a new test method.

ReviseStandards committees are typically very receptive to suggestions that might improve an existing standard.

The modification of an existing standardized method can be of great benefit to your company as well as to the industry as a whole. Revisions can occur as often as necessary and can reflect the rapid changes in technology.

ImageWorking together with the American Society for Testing and Materials (ASTM), we helped to publish a new guide for the axial, bending, and torsional durability testing of vascular stents. Each company involved was able to incorporate their own validated methods into this new standard.

Helping to develop new standards can be a time consuming process, but it allows you to collaborate with others in the industry that are struggling with the same issues and can often be an opportunity to build industry synergy and world-wide acceptance of universal design criteria.

In the next part of this series, we’ll look at more options for establishing a new test method.

For more information, please visit our website at http://www.medinstitute.com