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Combined usability studies for medical devices – the most important questions answered

Author: Marvin Kolb

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Dec 2023

With combined usability studies for several medical devices, you can carry out the summative evaluation or human factors validation of several medical devices in a resource-saving manner. In order to meet all regulatory requirements, to guarantee the most efficient implementation possible and to be able to argue correctly before the regulatory authorities, it is worth gaining a deeper understanding of the method.

We have compiled and answered 7 questions for you in this article. We probably won’t clear up all the uncertainties surrounding combined usability studies for medical devices, but we will answer the typical questions.

Enjoy reading!


1. What is a combined usability study for several medical devices?

Our definition (this term is coined by us and does not appear in any standard): “A conclusive and evaluative usability study in which multiple medical devices are tested together to demonstrate that the use of the devices is free of unacceptable risks.”

You can read the basics of the topic in our article “What are combined usability studies for multiple medical devices?”. Here you will find everything you need to know and an example of a combined study.


2. Can a combined study also be used for a summative test (summative evaluation, as well as human factors validation)?

Yes, you can use the combined test method for the summative evaluation of your products. We have tried this several times and have never had any problems. However, it is very important that you have a sound rationale for the selection of the chosen products and application scenarios and have a good understanding of why certain combinations make sense and others do not.


3. Is it possible to combine the user training of two products?

To understand this question, we recommend that you look at an example of a study, if applicable.

When we say “conduct the training together”, it only means that the users come to a single training session (if it is a pre-deployment training) and not to two separate training sessions, and that there is no interruption in the conduct of the trial between use cases to conduct the training for the second product. If they are accessories, you could even conduct a joint training session.


4. Can the summative usability study or human factors validation be combined with the design validation study?

In general – i.e. also for non-combined usability studies – the following applies: The summative evaluation is considered part of the validation of the device. Whether you can combine the summative usability study with the design validation depends on your product. In general, usability testing must be performed first to ensure that you are not exposing your users to unacceptable risks when testing your design in a clinical setting. You can usually start with a usability test and then add a clinical design validation part if the test itself did not reveal any critical errors.


5. Can combined testing take the approach that only the worst-case product, e.g. for a device group, is considered and argued?

Yes, you can reduce the number of products to be tested on the basis of a justification. The justification must then include an explanation of why the selected product is the most critical of the product group. In the best case, you have a design gap analysis that highlights the differences and use this as a starting point for the justification. Unfortunately, it’s not as simple as just selecting the products with the most features, as different controls for fewer features can also be critical. Therefore: The well-founded justification is important here.


6. If you are testing multiple medical devices in a usability study, how closely do you think the devices can be related if they are used for the same procedure? For example, when testing an HME and an ET tube?

Basically, you can test all products together that fit together in terms of the usage environment and/or the user group. They can be very similar, and if the handling is also very similar, you can even think about creating only one usability engineering file for all these products. That is, you would summarize them in a summative evaluation and argue why you are only testing certain products and not all of them. This needs to be a risk-based approach to selecting the products and usage scenarios, and then you would need to write a justification accordingly.


7. Can you use the same participant belonging to different user groups for different tasks in a study?

If the participant fits into both user groups: Yes, of course! This means that you have to recruit fewer participants. But you cannot count the participant twice. Meaning: You must have 15 participants for each task. These can be different participants, but they can also always be the same 15 participants.


Your question was not included?

Then please contact us via our contact form! We will help you to carry out your usability studies as pragmatically and resource-efficiently as possible!



Careful discussion of key questions will make it clear that such studies are an efficient way to evaluate the safety and usability of multiple medical devices simultaneously. The focus should always be on thorough planning and sound justification for the selection of products and scenarios, which is essential for the validity and efficiency of the study.

Our team of experts will be happy to answer any further questions and provide individual advice. Our aim is to help you design your usability studies as pragmatically and resource-efficiently as possible.

Do you want to know whether a combined study is worthwhile in your case? Let’s find out together! Get in touch using our contact form. We look forward to hearing from you.


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