Oral washes and tongue swabs for Xpert MTB/RIF Ultra-based tuberculosis diagnosis in people with and without the ability to make sputum

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Abstract
Background: Oral samples show promise for tuberculosis (TB) diagnosis. Data from different samples and people with sputum scarce TB are limited. Methods: We assessed Xpert MTB/RIF Ultra (Ultra) in symptomatic people at clinics (Cohort A, n=891) or at antiretroviral therapy (ART)-initiation without syndromic preselection (Cohort B, n=258). In Cohort A, we collected oral washes (OWs) and, separately, tongue swabs (flocked, foam with heat). In Cohort B, we collected OWs, three flocked tongue swabs (comparing one with heat to two pooled swabs) and, separately, buccal swabs, periodontal brushes. We offered sputum induction and did different culture methods on a subset of Cohort B tongue swabs. Results: In Cohort A, Ultra on OWs, flocked tongue and foam swabs had sensitivities of 80% (95% confidence interval 56, 94), 59% (53, 65) and 65% (58, 72) and high specificities. In Cohort B, OWs and single heated swabs had 71% (42, 92) and 64% (35, 87) sensitivity, respectively. Pooled tongue swabs, buccal swabs and periodontal brushes had low sensitivities. MGIT960 had the highest sensitivity [64% (35, 87)] of culture methods. Oral sampling detected TB in sputum-scarce people [Cohort A: 25% (7/28) flocked and foam swab-positive; Cohort B: 18% (10/56) OW-, 23% (13/56) single flocked swab-positive]. In Cohort B, this would at least double the people with a positive Ultra result (sputum or oral) if induction were unavailable. Conclusion: Ultra on OWs or foam tongue swabs has higher sensitivity than other oral-based approaches and detects sputum-scarce TB, resulted in more people diagnosed compared to Ultra on expectorated sputum.

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