When to “factor” in Human Factors

I have a confession: I knew very little about human factors about 10 years ago. In fact, at the time, I was in industry leading a project and my team and I met with FDA for input on the product design. When FDA indicated we need to do human factors, my thought was “say what?” We were being very intentional on the product design and we knew our users because it was a common disease state. We were also following design controls to conduct design verification testing and were planning for design validation. Now, I have to factor in one more thing? And how much of a difference is that going to make? Well, I was about to find out.

Once the angst about needing human factors had settled, we started down the path of planning for our formative. We were sure it would be a cinch. We do this one formative and then we’re on our way to validation! Then things took a turn. The product required a basic conversion, then drawing a drug and injecting. Simple, right? Well, we found out that of the intended users, many were unable to correctly convert. We also found that with as much effort we put into making the IFU look stellar and contain important information, hardly anyone noticed or read it. Instead, they quickly relied on what they were accustomed to. Watching the sessions was eye-opening, as if a veil was pulled away, and the outcomes we observed, had the potential to lead to harm.

From this experience, I had a major ‘AHA’ moment about human factors.

  • Human factors is a process that allows for an understanding of the intended users and where they will use the product. The who and the where will have factors that play into how the product is used. Understanding those elements help with product design and development.

  • Human factors applies to the full product user interface (e.g., packaging, device, IFU, training) because each aspect of the user interface is a point of information to the user and may influence how the user uses the product.

  • During testing, if use errors occur, human factors uncovers why they occurred, which then provides insight for making improvements to the product user interface.

    • Note: Human factors testing is not a pass or fail exercise. This was really hard for me to grasp at first! Therefore, the study design is important and study execution requires skill and some flexibility to gather the necessary data when users do unexpected things.

  • The goal of human factors is to ensure products are safe and effective.

Where does human factors fit in your project?

Integrating human factors early in the product development process is the ideal case for outcomes that are cost effective and efficient with timelines. The opposite is considering human factors as the last step prior to submission or after the submission, which could lead to changes that unexpectedly impact both budget and timeline (I know. I’ve been there!).

My experience led me to understand the value of the human factors process. Since then, I’ve come across several scenarios where companies feel the way I used to.

Scenario 1: Easy product
The product is easy to use so what can go wrong? Well, as engineers, we often perceive our design to be simple, easy or straightforward, but we are close to that design and the intricacies of the design. Once marketed, the people who will use the design are likely seeing it for the first time. The users are also very likely to have different skillsets, different experiences, and possibly multiple health conditions that affect their overall senses and their ability to reason or perform simple, easy, straightforward tasks. Human factors (e.g., contextual inquiry) gives insight on the users and ensures the design meets their practices and behaviors.

Scenario 2: Product launched prior to human factors requirements
Another scenario I’ve come across is around products that made it to market prior to human factors requirements, and now companies are needing to apply human factors to meet regulations. The product user interface may or may not be changing. If there is a change, it is perceived as a slight change. In this instance, companies seem to consider human factors as the last step, relying on the thought that it being on the market means that human factors testing will be a breeze. I wish I could agree, but in some cases, for products that have been around for years, users could have developed workarounds to achieve effective use. Human factors testing will uncover those workarounds which may not align with the labeling. Human factors will also uncover that the slight change to the user interface was actually a big change. For this scenario, it’s important to perform the use-related risk analysis and conduct at least one formative evaluation before jumping into the validation.

Scenario 3: Existing product for a new indication
A final scenario I’d like to mention is the instance of using an existing product for a new indication. The existing product may be working well for the current intended use, but that cannot be assumed for the new indication. Again, understanding your users is key. Consider a simple example: a drug for arthritis is combined with a device that was initially intended for adolescents. If the device is not modified for the users with arthritis, they may not be able to use the product. Hand strength is one obvious factor, but there could be others. Therefore, in this case too, the human factors process will identify the necessary design changes and ensure the product meets the users’ needs.

Final Thoughts

By sharing my experience and learnings, I want to encourage you to “factor” in human factors as early as possible in your project and see the value that it adds both to the end users and to you. That said, if you’re somewhere between feasibility and submission, and you haven’t already, bring human factors into the overall development process. When planning for human factors testing, don’t rush it but allocate the appropriate amount of time. It often takes more than 4 weeks to write the protocol, recruit participants, conduct the study and write the reports. In fact, multiple rounds of formative evaluations may even be required. Applying human factors can be complex, but having the right stakeholders is important. Involve internal resources and/or an external firm that understand the human factors process to identify a strategy that optimizes the user interface and brings quality medical products to market.


  • ANSI/AAMI/IEC 62366-1:2015+AMD1:2020 Medical devices – Part 1: Application of usability engineering to medical devices, including Amendment 1.

  • FDA guidance entitled, Applying Human Factors and Usability Engineering to Medical Devices that was published by CDRH, FDA on February 3, 2016.