"That is why I trust": A qualitative study on acceptability and feasibility of novel tongue swab diagnostics to assess people presenting with tuberculosis symptoms in Viet Nam and Zambia

Millions of tuberculosis (TB) cases are estimated to be undiagnosed and unreported annually. Sputum has been the primary approach for diagnostic testing but tongue swabs are being investigated as an alternative to expand testing. To understand potential uptake and implementation, we explored the acceptability, usability, and feasibility of tongue swab-based TB testing from the perspective of healthcare workers, people undergoing TB screening, and caregivers in Viet Nam and Zambia. We interviewed people with symptoms of TB, caregivers of children undergoing TB evaluation, and healthcare workers who collected tongue swabs (n = 76 participants) between September 2023 and February 2024. Interviews were analyzed using framework analysis to elucidate preferences, experiences, and acceptability of tongue swabs vs. sputum. Findings were further organized according to acceptability and feasibility to understand barriers and facilitators to uptake. Most participants preferred tongue swab to sputum collection. The perceived usability and feasibility of tongue swabs were high. Key themes that influenced the acceptability of tongue swabs included ease of use, diagnostic accuracy, diagnostic yield, hygiene, risk of TB transmission during sample collection, time to test result, and trust in healthcare workers and the health system. Across interviews, many participants described tongue swabs as a comfortable and easy way to test for TB, compared to the physical discomfort and difficulty expectorating sputum. Participants described tongue swab suitability for everyone, yet perceived diagnostic accuracy was crucial in shaping test preference. Tongue swab-based testing for TB is likely to be highly acceptable and feasible if incorporated into TB diagnostic guidelines.