Saliva test shows high accuracy for detecting tuberculosis

A simple saliva sample may offer a highly accurate and easier way to diagnose tuberculosis (TB), according to a new study led by researchers from the Yale School of Public Health (YSPH) and collaborators in Colombia. The findings suggest that saliva-based testing could expand access to TB diagnosis worldwide, especially for people who cannot easily produce sputum samples, the current testing standard.

The study, published in the journal Clinical Infectious Diseases, evaluated whether saliva could be used to detect TB using a widely available molecular laboratory test. Researchers found that the saliva test correctly identified more than 90% of patients with confirmed tuberculosis, while also showing high specificity — meaning it rarely produced false positives.

Tuberculosis remains one of the world’s leading infectious disease killers. In 2023 alone, an estimated 10.8 million people developed TB, and roughly one quarter of cases went undetected. Delays in diagnosis allow the disease to spread and make treatment more difficult. The new results suggest that saliva testing could help close that diagnostic gap.

“Tuberculosis testing has long relied on sputum, which can be difficult for many patients to produce,” said J. Lucian (Luke) Davis, MD, a professor in the Department of Epidemiology (Microbial Diseases) at YSPH and the Section of Pulmonary, Critical Care, and Sleep Medicine at Yale School of Medicine. “Our findings show that saliva can be a reliable and far more accessible sample for diagnosing TB.”

The research represents the first large clinical evaluation comparing saliva samples with oral swabs, which is another alternate testing method to sputum. The study was conducted in Cali, Colombia, where researchers enrolled hundreds of people undergoing evaluation for possible tuberculosis. Participants provided sputum, saliva, and oral swab samples for testing.

Among 190 participants included in the analysis — 95 patients with confirmed TB and 95 without — the saliva test demonstrated 90.5% sensitivity and 95.8% specificity, meaning it correctly detected TB in most infected individuals while accurately ruling it out in others.

Oral swabs, by comparison, detected about 72% of TB cases, making them significantly less sensitive than saliva samples.

The difference may stem from the amount of biological material collected in each sample, the researchers said. Saliva testing allows laboratories to analyze a larger volume of sample, which may increase the chance of detecting small amounts of Mycobacterium tuberculosis, the bacterium that causes TB.

“Our study shows that saliva likely captures more microbial material than oral swabs, which likely explains why it performed better,” said Deninson Alejandro Vargas, PhD, a researcher at the Centro Internacional de Entrenamiento e Investigaciones Médicas (CIDEIM) and Universidad Icesi in Cali, Colombia, and the study’s lead author. “Our results show that saliva testing could be a promising alternative for testing for TB in real-world clinical settings.”

Another important advantage is convenience. Collecting sputum often requires patients to cough deeply to bring up mucus from the lungs, a process that can be uncomfortable or impossible for some people. Children, individuals living with HIV, and patients with early or mild disease frequently struggle to produce sputum samples. Saliva collection, by contrast, involves simply drooling into a sterile container. With saliva samples easy to collect, saliva testing could be applied outside of hospitals and clinics, the researchers said.

The current research builds on a long-standing collaboration between YSPH and CIDEIM at Universidad Icesi in Colombia, which has focused on improving TB diagnostics and training researchers in infectious disease science.

While these initial results are highly promising, the researchers said additional studies are needed to evaluate how well saliva testing works in broader populations, including people with fewer symptoms, children, and those screened outside traditional clinical settings.

Still, the findings mark an important step toward simpler and more accessible TB diagnosis.

“Improving TB detection is one of the most important steps toward controlling the disease globally,” said Davis, co-senior author of the study and an international expert on TB. “If we can diagnose TB with something as simple as a saliva sample, we could dramatically expand access to testing and reach people who might otherwise go undiagnosed.”