How to demonstrate that users understand labeling?

We are being challenged by a regulatory body to provide evidence that users can understand the contraindication and warning statements in our Instructions for Use (IFU).

I'm not sure how to go about this.

The often-used "readability" metrics (e.g. "Flesch reading ease" or "Flesch-Kincaid Grade Level") are inappropriate, as they rely on syllables-per-word, and there are some unavoidable multi-syllable words due to the nature of the device (and by the "canned" warnings from guidances).

I've thought about a study where subjects read each statement aloud, and self-report whether they understand or not, but there are many specific contraindications that most people would not understand unless they had the particular condition. (The device is for home-use, and even the word "contraindication" may be problematic...)

Questions for discussion:
- Anyone else had to demonstrate user comprehension of contraindications/warnings?
- How would you go about providing such evidence?

 

1. Who is that regulatory body? This is important for regulatory context.
2. Have you consulted IEC 62366? It has some guidance in its annexes.

 

It's the US FDA.

The main difficulty here (as I see it) is that contraindications and warnings are essentially instructions worded in the negative ("Do not..", "Never.."), whereas most of the usability guidance is with respect to confirming comprehension of actionable instructions ("Do this...", "Check this...").

We've done a usability study in which subjects are presented with the instructions, and monitored as to how they use the device. It was pretty clear they could follow the actionable instructions just fine (i.e. they could use the device as intended, according to the instructions). ...and this is a pretty straight forward way to demonstrate comprehension of the actionable instructions to the satisfaction of the FDA.

...but as to how you'd go about demonstrating comprehension of prohibitive instructions - this is what I'm struggling with.

 

Hi MarkMeer,
I just joined and read this so it might be a little too late - but the USA does have a Human Factors guidance document that is quite useful>
Link is here - let me know if you have any questions.
Kind regards
Diana