Tongue Swab Xpert MTB/RIF Ultra Testing for Tuberculosis in Adolescents: A Cross-sectional Study of Diagnostic Accuracy and Acceptability.

Background: Improved diagnostics are needed for tuberculosis (TB) among adolescents. Tongue swab (TS) molecular testing is a promising strategy for TB testing. We evaluated diagnostic accuracy and acceptability of Xpert MTB/RIF Ultra ("Xpert") using TSs for TB detection in adolescents. Methods: We conducted a cross-sectional diagnostic accuracy study in southern Vietnam. Adolescents aged 10-19 years who were recommended to undergo investigation for TB were eligible. Participants provided TS and sputum samples and were surveyed regarding sampling experiences. TS samples were tested on Xpert, with sputum tested on Xpert and liquid culture. We utilized a composite reference standard of a positive sputum Xpert or culture result to define disease status. Sensitivity, specificity, and diagnostic yield were calculated for TS Xpert. Results: From July to December 2025, we enrolled 225 adolescents. Most participants (157/225 [70%]) were close contacts of a person recently diagnosed with TB and many (129/225 [57%]) did not exhibit symptoms of presumptive TB. All adolescents could provide a TS, while 116 (52%) could produce mucopurulent sputum. Tuberculosis prevalence was relatively low (12/225 [5.3%]). TS Xpert sensitivity and specificity were 58.3% (90% confidence interval [CI], 35.6%-78.0%) and 99.5% (90% CI, 97.9%-99.9%), respectively. TS diagnostic yield among all diagnosed was 58.3% (7/12). TS sampling was highly acceptable to adolescents; the quickness and simplicity of collecting TSs were considered favorably. Conclusions: TS Xpert sensitivity and diagnostic yield were relatively low among adolescents recommended for TB investigation. All participants were able to provide a TS. Specificity was excellent. TS's high acceptability indicates it remains a promising sample for diagnostic algorithms.