Oral Washes and Tongue Swabs for Xpert MTB/RIF Ultra-Based Tuberculosis Diagnosis in People With and Without the Ability to Make Sputum

Abstract

Background: Oral samples show promise for tuberculosis (TB) diagnosis, but data from different sample types and sputum-scarce individuals remain limited.

Methods: We evaluated Xpert MTB/RIF Ultra (Ultra) in symptomatic clinic attendees (cohort A, n = 891) and people initiating antiretroviral therapy without symptom screening (cohort B, n = 258). In cohort A, we collected oral washes (OWs) and, separately, tongue swabs (flocked or foam with heat). In cohort B, we collected OWs, 3 flocked tongue swabs (1 heated, 2 pooled), and, separately, buccal swabs and periodontal brushes. Sputum induction was offered, and different culture methods were applied to a subset of cohort B tongue swabs.

Results: In cohort A, Ultra sensitivity was 80% (95% confidence interval [CI], 56%-94%) for OWs, 59% (95% CI, 53%-65%) for flocked swabs, and 65% (95% CI, 58%-72%) for foam swabs, with high specificity. Foam swabs detected more people with Ultra sputum semi-quantitation categories of low or less than flocked swabs (53% [95% CI, 41%-64%] vs 37% [95% CI, 29%-46%]). In cohort B, OWs and single heated swabs had sensitivities of 71% (95% CI, 42%-92%) and 64% (95% CI, 35%-87%), respectively. Pooled tongue swabs, buccal swabs, and brushes had lower sensitivity. MGIT960 showed the highest sensitivity (64% [95% CI, 35%-87%]) among culture methods. Oral sampling identified TB in sputum-scarce people: 25% (7/28) positive by flocked or foam swabs (cohort A); 18% (10/56) were OW and 23% (13/56) single swab positive (cohort B). In cohort B, this could double Ultra positivity if induction were unavailable.

Conclusions: Ultra on OWs or foam swabs offers higher sensitivity than other oral methods and effectively detects TB in sputum-scarce individuals.

Keywords: Xpert MTB/RIF Ultra; oral washes; tongue swabs; tuberculosis.