Usability vulnerabilities of elderly adults in at-home COVID-19 self-test kits: findings from a South Korea usability study

The COVID-19 pandemic led to the widespread adoption of at-home COVID-19 self-test kits as accessible alternatives to clinical diagnostics. However, laypersons may have a limited understanding of use-related risk when operating these devices. Identifying how demographic factors such as sex, education level, and age influence use errors can guide improvements in the usability and safety of home-based medical devices. We recorded the frequency of use errors for each participant, along with their self-rated task understanding and satisfaction on a 5-point scale. We analyzed this data to compare error rates across different age, sex, and education groups. Furthermore, we used statistical models to determine the influence of these demographic factors on the likelihood of error occurrence and the total number of errors. Self-rated task understanding and satisfaction scores were also compared between participants who did and did not commit errors. A total of 52 participants (17.2%) committed at least one use error, resulting in 123 errors recorded in total. Error rates increased markedly with age, ranging from 0% among adolescents (14–19 years), 7.25% in participants in their 20s, 5.08% in their 30s, 16.67% in their 40s, 30.77% in their 50s, 46.15% in their 60s, to 100% in participants in their 70s. Each additional year of age was associated with a 9.5% increase in the odds of any use error (OR = 1.095, 95% CI 1.064–1.127; p < 0.001) and a 7.9% increase in error counts (IRR = 1.079, 95% CI 1.053–1.106; p < 0.001) in pooled models adjusted for kit and calendar time. Tasks involving buffer dispensing and sample mixing were the most error-prone. Participants who committed errors reported significantly lower self-rated task understanding and satisfaction, with the effect especially pronounced among those aged 60 and above. Age significantly affected the usability of COVID-19 self-test kits, with older adults being more prone to errors, likely due to cognitive misunderstandings rather than physical limitations. Simplifying task steps and improving interface clarity, when tailored to older users’ cognitive needs, are crucial for safer use. These findings suggest that age-inclusive design improvements and clearer instructions can support safer and more effective self-testing for users of all ages.