Lateral flow tests are becoming part of the new normal in the ongoing COVID-19 pandemic. I first got access to the tests as a parent of 2 primary school children but they are now becoming common for all adults in workplaces throughout the UK. While there is debate at the effectiveness of lateral flow testing, as someone who works in the medical device industry, I’ll take any opportunity to experience using new medical developments first-hand.

Opening the first box of lateral flow tests reminded me of one of my first Human Factors projects as a consultant in 2008. I was running a usability study in which users had to perform a home-based glucose tolerance test. The users had to prick their finger with a lancet, place the blood drop onto a sensor, drink a glucose drink, wait a period, then take a second blood sample, place it on a sensor and then finally send the samples back to a lab for analysis. The system was paper-based and it quickly became clear through user testing, how important all the different parts of the device were. We spent time (and blood) trying to figure out which was the most intuitive lancet for naïve users, and quickly found out that many lancets were not obvious to use. We also had to figure out how everything would be packaged together, so that users would have easy access to all parts of the test when they received it in the post.

Testing home kits was challenging

One of the biggest challenges of usability testing the home kits was communicating to users where and how to place their blood since this had to be very precise. There were numerous iterations of the overall design and instructions and many formative studies were conducted before we felt confident that we had a design that would work in real-life. For me, it was a lesson of how subtle changes to the design can have a big impact on usability and how user testing is imperative to help make decisions about these changes.

Eliminating risk is crucial

Medical device development follows a risk-based approach to ensure the design is safe to use. Standards such as IEC 62366-1: 2015, ISO 14971: 2019, FDA Applying Human Factors and Usability Engineering to Medical Devices: 2016 and MHRA Guidance on applying Human Factors to medical devices: 2021 follow the process shown below.

The FDA describes the best ways to eliminate risk in order of preference as follows:

1. Inherent safety by design – For example:
• Use specific connectors that cannot be connected to the wrong component.
• Remove features that can be mistakenly selected or eliminate an interaction when it could lead to use error.
• Improve the detectability or readability of controls, labels, and displays.
• Automate device functions that are prone to use error when users perform the task manually.

2. Protective measures in the medical device itself or in the manufacturing process – For example:
• Incorporate safety mechanisms such as physical safety guards, shielded elements, or software or hardware interlocks.
• Include warning screens to advise the user of essential conditions that should exist prior to proceeding with device use, such as specific data entry.
• Use alerts for hazardous conditions, such as a “low battery” alert when an unexpected loss of the device’s operation could cause harm or death.
• Use device technologies that require less maintenance or are “maintenance free.”

3. Information for safety – For example:
• Provide written information, such as warning or caution statements in the user manual that highlight and clearly discuss the use-related hazard.
• Train users to avoid the use error.

As you will have noticed in the FDA Human Factors guidance, information for safety is often seen as the third or least preferred option. But in cases such as a home diagnostic, the instructions for use (IFU) becomes integral to the design and therefore is not simply a separate control measure but part of the design itself and requires rigorous testing and consideration of Human Factors.

A well written and designed Instructions for Use

I’ve seen a lot of poor Instructions for Use (IFUs) and Quick Reference Guides (QRGs) accompanying home kits over the years, both as a consumer and a Human Factors consultant, and I’m pleased to say that the NHS COVID-19 lateral flow test is not one of those.

Some of the key design elements of the instructions are:
• Information is broken down into steps which are easy to digest and presented under clear section headings
• Good font size and use of white space
• Concise sentences written in plain English
• Line drawings which clearly represent the test kit
• Appropriately sized booklet which is easy to handle
Alternative ways to view the instructions are available – including watching a video or easy read and large print guides.

Inspired Usability can help with the design, usability testing or expert review of instructions for use and quick reference guides. For more information, see our website.