Human Factors for Medical Devices
(Part I): The Invisible Testing Your Medical Device Needs

Getting FDA clearance is a critical milestone in medical device commercialization. However, it does not mean your medical device will sell. Neither do patents, investor dollars, or a killer sales strategy. These things are necessary for success but they don’t guarantee user adoption.

User adoption depends in large part on whether or not clinicians are happy with your device. How can you predict that they will be? Through reliable data.

When it’s time to show your device to users, compliments are great, but quantifiable data is more dependable. That data comes from Human Factors Testing, which can reliably interpret the seemingly amorphous world of user perception.

In this blog article, you’ll learn what Human Factors Testing is, what type the FDA wants, and how it can make your device more market-ready.

Kim Najjar

Senior Industrial Designer

Human Factors and the FDA

Human Factors tests reveal how well a user interacts with your device.

You’re probably already familiar with Human Factors tests like one-on-one interviews, prototype demonstrations, and surveys. Data from these tests is usually qualitative, but that doesn’t mean it’s “soft” or “unreliable.” On the contrary, well-designed human factors tests give hard evidence that users have excellent or unfavorable interactions with a device.

A user having an unfavorable interaction might make mistakes, feel confused, be inefficient, or experience physical discomfort while performing tasks. Good interactions, by contrast, are characterized by confidence, error-free performance, speed, comfort, and a sense of satisfaction. Medical devices that promote good interactions reap benefits like patient safety, treatment efficacy, and market success.

It’s no wonder the FDA requires evidence of good Human Factors as part of every pre-market submission. It’s just as important as any other required data, including clinical testing, EST/EMC testing, and biocompatibility testing.

However, just because you have to do it as matter of course does not mean that Human Factors Testing for the FDA will help you learn about user adoption. That assumption is incorrect for the reasons listed below:

The FDA focuses on only one part of Human Factors testing: the user interface of a device.

A guidance document from 2016 states:“[The FDA] recommends that manufacturers follow human factors or usability engineering processes during the development of new medical devices, focusing specifically on the user interface…” (Applying Human Factors and Usability Engineering to Medical Devices).
User interfaces comprise any feature that a person manipulates to achieve device function. Such features can be physical (with levers, handles, etc.) or virtual (with buttons in an app or software).
Devices can utilize only physical (ex., forceps), only virtual (ex., patient information database), or a mixture of both types of controls (ex., ultrasound machine). Sound and indicator lights are also aspects of a user interface, if present.
While it’s vital that users can correctly use your device, their perception of it is also crucial to success, specifically market success. That can be predicted with user perception testing.

Some devices need almost no Human Factors testing to satisfy the FDA.

That’s less than any product needs - even Post-It notes undergo more! You may be surprised by your device’s reception if you do so little.
On the flip side, some devices need hundreds of subjects and formal protocols. All that work may give you confidence, but it’s still not guaranteed to tell you about user adoption.
In either case, the recommended amount of testing can misrepresent how much actually needs to be done. That is because the recommendation is determined through risk analysis.
The draft guidance document from 2022, “Content of Human Factors Information in Medical Device Marketing Submissions,” defines three levels of Human Factors testing. (Keep in mind that, while helpful, as a draft it is non-binding and subject to change.) The first level needs a mere summary of usability testing activities, while a full validation study accompanies the third level.

The FDA only cares about data that relates to safety and efficacy.

Based on their 2016 guidance document, “Applying Human Factors and Usability Engineering to Medical Devices,” it states, “While following [human factors and usability engineering] processes can be beneficial for optimizing user interfaces in other respects (e.g., maximizing ease of use, efficiency, and user satisfaction), FDA is primarily concerned that devices are safe and effective for the intended users, uses, and use environments.”

Safety and efficacy are the most important aspects of a medical device, but even the FDA acknowledges that they are distinct from user satisfaction and perception (see quote above).

Satisfied users are crucial to making your device a hit on the market. That’s why it’s important to conduct additional Human Factors Testing, even though it won’t be seen by the FDA. Fortunately, you can often test different areas of Human Factors simultaneously because the methods are similar. It all depends on how you set up the tests.

But if risk-oriented and market-oriented Human Factors tests are similar enough to be conducted simultaneously, what exactly makes them distinct?

A Worst-Case Scenario

One way to think about the difference is that FDA human factors testing is important to whether it can sell, but market-oriented human factors testing focuses on whether it will sell.

We already know that the FDA’s purpose is to ensure safe and effective medical devices. Companies have the additional purpose of creating or enhancing value, so they need to make products people want to buy.

Being in the dark about that aspect of your device can lead to design missteps that prevent the widespread use of your technology, even if it has real health benefits.

Let’s look at a theoretical example.

You designed a flow sensor for Foley drainage catheters. It wirelessly transmits information about urine quantity and composition to a patient’s care physician, eliminating the mistakes and hassle of manual note-taking. The sensor is reasonably small, compatible with any catheter on the market, and adds less than $100 to the cost of the drainage system.
The FDA considers it a Human Factors Submission Category 3 device and requires full Human Factors validation. (Note that the submission category is independent of a device’s class) Fortunately, your human factors testing, which happens throughout several patient studies over a year, successfully demonstrates that user errors are minimal. Physicians can install it, and home caretakers can maintain it. You do not test patients because such studies were not required and would have added complexity. The FDA gives you market clearance with little back-and-forth.
You start manufacturing efforts and training campaigns, but sales stall almost immediately.
The sensors are functional, and the salespeople are competent, so you interview physicians to find answers. You pick several from across the country that you’ve never talked to before. Their feedback is consistent and runs along the lines of, “Our patients call all the time complaining that the sensor isn’t working. But nothing is actually wrong with it. They just re-install it backward during daily cleaning. They come in all the time and we have to spend unpaid time just to turn it around. So, I stopped using them. It’s easier to have them take notes.”
Worried, you overhaul your training and marketing materials. You hire more representatives to give demonstrations about correct installation. However, hospitals still fail to spend enough time training patients and mistakes continue to happen. Revenue figures never become strong enough to support continued production, and you’re forced to re-design the sensor and re-submit it to the FDA. By then, a competitor has released a similar device with a more intuitive interface that quickly takes over the market.

It’s easy to see that patient feedback, not just from healthcare professionals, was missing from the sensor’s development. Why didn’t the FDA require actual patient data? The reason is that a hazard analysis concluded that there was no risk of patients harming themselves while using the device. Therefore, there were no critical tasks for the FDA to review. So, installing the sensor backward was not dangerous, even though it was inconvenient. Inconvenience led to unpopularity and that caused its market failure.

Extra Human Factors Testing might have prevented user mistakes. Elderly people, more representative of the patient population, could have been tested informally to reveal user problems. It might have led to the detection of the connection error, leading to a quick re-design before FDA submission and a more successful launch, which would have been due not only to a lack of customer complaints but also to the intangible benefits of user satisfaction.

After discussing how user satisfaction is good for business, how exactly does it work?

A Best-Case Scenario

If we continue the theoretical example, assuming you re-designed the sensor before it hit the market, the next steps might have looked like this:

After the Foley flow sensor launches, your sales team secures a few orders in select hospitals across the country.
You soon see physicians posting reviews and demonstrations of the flow sensor online. They upload videos, recommend them on social media platforms, and mention them on their practice’s websites. The feedback is overwhelmingly positive: “Since I can monitor my patients remotely, they need fewer appointments. I love how the sensor works with every size and brand of Foley we use. And, the patients have no difficulty with it at home.”
Even though you don’t hire more salespeople, your sales increase because of this word-of-mouth advertising.
When your competitor’s version of the device comes out a year later, it is only able to take about a quarter of the market. You use your profits to develop more devices, and because of your company’s good reputation, healthcare facilities are quick to adopt them.

Extra testing clearly has benefits: it helps you make devices that are easy to use and fit into existing workflows. These are both hallmarks of good human factors, meaning minimal effort is needed to reap a device’s rewards. It leads to user satisfaction, spontaneous recommendations, and device adoption, ultimately improving a company’s reputation. Future successes are then easier, because users prefer to buy from companies that have provided good experiences in the past.

The Cost of “Invisible” Testing

Even if you’re convinced of its benefits, the difficulty of adding Human Factors tests can seem like an insurmountable change in the development plan. It’s not hard to integrate, though, for several reasons:

Market-oriented Human Factors Testing is a well-established practice, so you don’t have to spend excess time with trial and error. In fact, it is routine and expected in all product development industries, from cars to software interfaces. Medical device developers use many of the same techniques.
Documentation need not be as stringent when conducting internal formative tests. Good documentation practices should always be followed when capturing data, but since the FDA won’t see market-oriented data, your reports may not need to be as detailed or be reviewed by as many people.
You can combine market-oriented Human Factors Tests with risk-oriented ones as secondary endpoints. If you have a physician booked for a risk-oriented test, tweak the protocol slightly by asking more questions or adding a few more minutes of playing with prototypes.

However easy it is to add Human Factors tests, they still add some time and expense on the front end of development. Most of this is due not to the testing but to making design changes that otherwise would not have happened.

Returning to the sensor scenario, let’s say you discovered the patient error early and decided to re-design the device. You would have had to perform more rounds of design and prototyping, potentially taking several months and thousands of dollars. While hard to sell to investors, the change would have been considered cheaper than the cost of launching a product that floundered. In addition, the change would have allowed your device to elevate the standard of care.

That’s the ultimate point of thorough Human Factors Testing - while it’s good for your bottom line, it’s ultimately good because it helps your revolutionary treatment reach as many people as possible.

Now What?

After reading this blog, try some market-oriented Human Factors testing. After all, wouldn’t you want a peek into your device’s commercial future? If that’s the case, learn more about the process in the next installment (Part 2) of this blog. Better yet, schedule a free consultation with our design team at Biotex. We’d love to sit down and talk to you about your device and goals so we can recommend a test plan.

At Biotex, our team has the resources in-house to conduct risk-and-market-based testing, from writing protocols to providing users from our extensive network of contacts.

Reach out to us today!

About the author:

Kim Najjar is a Senior Industrial Designer at Biotex, Inc., where she helps clients develop new medical devices by visualizing, prototyping, and testing their ideas. During device development, Kim consistently advocates for users' needs, whether they’re physicians, technicians, or patients. She is proud to be a part of Houston's thriving medical device innovation industry for over seven years.