Tongue swab Xpert MTB/RIF Ultra testing for TB using a revised consensus protocol.

Area of Science:

• Microbiology
• Infectious Diseases
• Diagnostics

Background:

• Tongue swabs are a promising specimen for tuberculosis (TB) diagnosis.
• Previous Xpert Ultra testing of tongue swabs had a notable rate of non-actionable results (6.1%).

Purpose of the Study:

• To evaluate a revised protocol for tongue swab processing and Xpert Ultra testing for TB diagnosis.
• To assess the error rates and diagnostic performance of the revised protocol in high-burden countries.

Main Methods:

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

Main Results:

• The revised protocol resulted in an overall non-actionable result rate of 5.6%, with rates below 4% in most countries, except 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).

Conclusions:

• The revised tongue swab protocol demonstrates reduced non-actionable results at most study sites.
• Tongue swabs processed with the revised protocol offer moderate sensitivity and high specificity, supporting their use as an alternative specimen for Xpert Ultra TB testing when sputum is unavailable.