By David Orenstein, Product Development Engineer (EG-GILERO)
It can be difficult sometimes to see the value in usability testing. As devices are developed they seem so simple to the engineering team developing them; or the complexities are so justified it wouldn’t make sense to do it any other way. Often it is true that the final design is essential in order for the commercial device to be effective even if it is complex. That does not mean that the final design is intuitive to its target user group who lacks an understanding of why the device was designed the way it is. To make my point more tangible let’s consider pen injectors. A study published in April of 2017 titled Errors in the Administration Technique of Insulin Pen Devices: A result of Insufficient Education; outlines three use cases that are described and analyzed. The full article may be found on the National Center for Biotechnology Information website, but I will summarize the three use cases for you here to drive my point:
- User 1
- A middle-aged Caucasian male with type-1 diabetes reported to his doctor that he did not like using insulin pens and reported them “to be a hassle compared to vial and syringe.” When asked to demonstrate his use of the device he “took an insulin syringe, injected the syringe into his pen device, dialed the device to 5 units and pushed the plunger.” He would then pull the insulin syringe out of the pen device and inject the “contents” into his body with the syringe. I write contents in quotes because his syringe was reported to be essentially empty when disconnecting it from the pen device. According to the user’s electronic medical record (EMR) he had never even purchased a pen needle.
- User 2
- An African-American female senior citizen diagnosed with type 2 diabetes was prescribed to use a determir flexpen in addition to her oral medication. When questioned regarding whether or not she was experiencing any difficulty using the pen device; she stated “it ‘spills out on the skin’ before the entire dose is given.” Unsure what this meant the user was asked to demonstrate her use of the pen device. “She placed the pen needle on the pen device and securely screwed it on. She removed the outer cap of the needle, then dialed the device up to 20 units and attempted to inject without removing the inner cap.” The user had injected the entire dose into the inner cap, which was too small for the dispense volume, hence it “spills out on the skin.” It was reported that the insulin never even made its ways into the pen needle and was not injected into her body.
- User 3
- A 55 year old Hispanic female suffering from type 2 diabetes was ordered to switch from bolus injections via vial and syringe to pen needle for ease of use and transportation, but provided no training on how to use the pen device. When questioned for feedback regarding her experience using the device the patient stated – “her blood sugars were not improving and she wanted to know how long each pen should last.” The investigator asked to inspect the pen device and discovered that it still contained all of its insulin. Puzzled, the investigator asked the patient to demonstrate her technique. The patient assembled the pen needle to the device, dialed the device to 10 units per physician’s orders, and removed the inner and outer caps. Her misuse occurred during the delivery. The patient injected the needle into body, but did not depress the plunger to depress the medication. Instead she rotated the dial 10 to 0.
These seem like simple errors, but at the end of the day they can have a disastrous impact to a patient’s health. Neither patient in all three cases was actually injecting insulin into their body; and may have been performing these errors for months before they were identified by a HCP.
Consider this; per FDA guidance Applying Human Factors and Usability Engineering to Medical Devices your validation study generally should have a minimum of 15 users per user group2; which would mean 20% of your study participants just failed the study in a critical manner. Do you think the FDA will be okay with those results? This is why formative and summative human factors usability testing is so valuable. A device recall can be much more costly than the HF testing, and ultimately our collective goal should be to release products on the market that help to make a difference. Had usability testing been performed early on, these misuses would likely have been identified prior to market release; and the manufacturer would have had the opportunity to develop a sound solution to mitigate the risk of these misuses occurring.
 Truong, Teresa H., Ngyuen, Trang T., Armor, Becky L., and Farley, Jamie R. “Errors in the Administration Technique of Insulin Pen Devices: A Result of Insufficient Education.” U.S. National Library of Medicine; National Institutes of Health. March 4, 2017. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5380504/ (accessed February 15, 2019).
 U.S. Department of Health and Human Services; Food and Drug Administration; Center for Devices and Radiological Health; Office of Device Evaluation. “Applying Human Factors and Usability Engineering to Medical Devices – Guidance for Industry and Food and Drug Administration Staff.” U.S. Food & Drug Administration. February 3, 2016. https://www.fda.gov/downloads/medicaldevices/…/ucm259760.pdf (accessed February 15, 2019).