Saliva Testing Shows Promise For Pulmonary Tuberculosis Diagnosis

Pulmonary tuberculosis diagnosis often relies on sputum, which can be difficult to obtain from certain patient groups.

Researchers in Colombia evaluated saliva and oral swabs among adults and children assessed for TB at primary care centres.

The study was conducted as a nested case-control design within a prospective cohort enrolled between July 2023 and August 2024.

Participants provided sputum for liquid mycobacterial culture alongside paired saliva and nylon flocked oral swabs.

A blinded microbiologist conducted molecular testing on thawed saliva and swab eluate, each mixed 1:1 with sample reagent, with diagnostic performance assessed against sputum culture.

Of 648 participants, saliva and oral swabs were tested from all 95 individuals with culture-confirmed TB and 95 matched culture-negative controls.

Saliva achieved a sensitivity of 90.5% and specificity of 95.8%, outperforming oral swabs, which showed 71.6% sensitivity and 99% specificity.

The absolute sensitivity advantage of saliva over swabs was 18.9%, while specificity was similar.

These results suggest both oral specimens are promising for TB diagnosis, with saliva offering stronger case detection potential.

The study addresses a critical diagnostic gap. Sputum collection can be challenging, particularly for children, people with HIV, asymptomatic individuals, and patients with nonproductive coughs. It also requires strict airborne infection control.

Saliva and oral swabs, by contrast, are minimally invasive and highly acceptable, with over 95% of participants reporting satisfaction with collection procedures.

Notably, saliva sensitivity exceeded the 80% minimum target for low-complexity, non-sputum TB tests.

These findings support saliva as a practical, accurate alternative specimen that could expand microbiological confirmation of pulmonary tuberculosis.

Adoption of saliva-based testing may improve case finding in clinics and community settings, particularly where sputum collection is difficult, helping to strengthen TB control efforts globally.

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