Tongue Swab Xpert MTB/RIF Ultra Testing for Tuberculosis Using a Revised Consensus Protocol: A multi-country...

Area of Science:

• Microbiology
• Infectious Diseases
• Diagnostics

Background:

• Tongue swabs show promise for tuberculosis (TB) diagnosis.
• Previous protocols using Xpert MTB/RIF Ultra had a notable rate of non-actionable results (6.1%).
• A revised protocol was evaluated in four high TB burden countries.

Purpose of the Study:

• To evaluate a revised tongue swab protocol for tuberculosis diagnosis using Xpert MTB/RIF Ultra.
• To assess the diagnostic performance and error rates of the revised protocol compared to sputum-based tests.

Main Methods:

• 1168 participants aged ≥12 years with presumptive TB were enrolled from outpatient clinics in the Philippines, South Africa, Nigeria, and Zambia.
• Tongue swabs were processed using a revised protocol with diluted Sample Reagent (SR) and tested with Xpert Ultra.
• Diagnostic performance was assessed against a culture-based reference standard.

Main Results:

• The overall proportion of non-actionable results was 5.6%, with significant variation by country (South Africa: 15.4%).
• Tongue swab sensitivity was 66.0% (95% CI 59.0-72.5) and specificity was 99.6% (95% CI 98.9-99.9).
• The revised protocol demonstrated low error rates at most study sites.

Conclusions:

• The revised tongue swab protocol is effective, with low error rates in most settings.
• Tongue swabs provide moderate sensitivity and high specificity for TB diagnosis.
• This method serves as a valuable alternative diagnostic tool when sputum collection is not feasible.