Rapid diagnostic self-tests have emerged as effective tools for identifying and controlling the spread of SARS-CoV-2. However, little is known about their acceptability and usability among populations under socioeconomic vulnerability globally. We aimed to evaluate the acceptability and usability of a COVID-19 antigen self-test among persons living in Salvador and Rio de Janeiro, Brazil. In this cross-sectional study (January–May 2023), participants used a COVID-19 antigen self-test in a simulated real-world setting, guided by an instructional video. Usability was assessed through two main outcomes: comprehension of instructions and proper execution of self-test (Poisson regression model); and accuracy in interpretation of self-test results (Cohen’s kappa). Acceptability was evaluated based on willingness to reuse the self-test, user experience, and recommendation to others. Among 437 participants, most were women (65.7%), self-identified as Black/ Pardo (mixed-race) (81.5%), aged 35 + years (65.7%), had a household income ≤ USD 470 (70.0%) and had completed secondary education (46.2%). Despite some procedural difficulties, most participants obtained valid results (88.1%), higher in Salvador (95.2%) than in Rio de Janeiro (81.7%) (p < 0.001). Participants showed difficulty interpreting test results, particularly inconclusive with a positive mark (32.9% correct) and faint positive markers (25.2% correct). Accuracy in interpretation was 89.6%, with moderate to substantial inter-rater agreement (Cohen’s kappa = 0.56 overall, reaching 0.78 among participants aged 35–44 years). Participants with older age, lower education level and self-identified as men had lower likelihood of obtaining valid results in adjusted model, and increased difficulties in test setup and interpretation. Over 95% of participants were willing to reuse and recommended the self-test. This study revealed high acceptability and usability of the COVID-19 antigen self-test among populations under socioeconomic vulnerability in Brazil. However, misinterpretation poses public and individual health risks, underscoring the need of simplified, multimodal and accessible instructions.
Castanheira et al. (Thu,) studied this question.