International – Human factors studies: Considerations for recruiting rare and complex user populations

Imagine you are preparing for a human factors (HF) validation study to bring your medical device to market, and the market research recruiters inform you that it will be very challenging, if not unfeasible, to recruit the required 15 participants per user group. What do you do?

It is not uncommon for some user populations, especially patient populations with rare or debilitating conditions, to prove difficult to recruit. As such, it is important to understand the various considerations for successfully and effectively including representative patient populations in HF validation studies.

Patient characteristics

In some cases, it might be necessary to include “proxy” users—individuals who are not intended users of your product, but whose characteristics align with those of your intended users. In these cases, we know that it is important to compare multiple characteristics (e.g., age, education, literacy level, sensory or physical impairments) to ensure the proxy users are representative of intended users.

Investigators should also look beyond the physical and demographic characteristics and consider intended users’ mentality towards a specific chronic condition. For example, imagine you are developing an autoinjector used to treat Growth Hormone Deficiency (GHD) in adolescents, but you’re having difficulty recruiting adolescents with GHD because of its relatively low incidence rate. Typically, GHD does not result in sensory or physical limitations, so it appears on the surface that the main characteristics you should look for in the injection experienced proxy users is experience treating a condition using injection devices…