Diagnostic Accuracy of Molecular Testing on Saliva and Oral Swabs for Pulmonary Tuberculosis.
Deninson Alejandro Vargas, Jose Fernando Fuertes-Bucheli, Andrea Sanchez-Hidalgo, Jairo Palomares Velosa, Alvaro Mauricio Lasso, Amanda J Gupta, Alvaro J Martinez-Valencia, Gustavo Díaz, et al. (12 authors)
Clinical infectious diseases : an official publication of the Infectious Diseases Society of America · 2026-03
Abstract
BACKGROUND: Rapid, accurate, nonsputum tests are needed to close gaps in tuberculosis (TB) detection. We evaluated the diagnostic performance of molecular testing on saliva and oral swabs.
METHODS: We conducted a nested case-control study with 1:1 incidence-density sampling within a prospective cohort of adults and children undergoing evaluation for pulmonary TB at primary care centers in Colombia (July 2023-August 2024). Participants provided a sputum sample for liquid mycobacterial culture and paired saliva and nylon-flocked oral swabs for storage at -80°C. A microbiologist blinded to clinical and culture data performed Xpert MTB/RIF Ultra on thawed saliva and on swab eluate, each mixed 1:1 with sample reagent. We calculated the sensitivity and specificity of saliva and swab against sputum culture and compared them using McNemar's test.
RESULTS: Among 648 enrolled participants, we tested saliva and swabs from all 95 individuals with culture-confirmed TB and 95 matched culture-negative controls (n = 190). Saliva sensitivity was 90.5% (95% confidence interval [CI], 82.8-95.6), and specificity was 95.8% (95% CI, 89.6-98.8). Swab sensitivity was 71.6% (95% CI, 61.4-80.4), and specificity was 99% (95% CI, 94.3-100). Saliva sensitivity exceeded that of swab by an absolute difference of 18.9% (95% CI, +10.0 to +27.9, P < .001), but there was no significant difference in specificity (-3.2%, 95% CI, -7.7 to +1.4, P = .25). Over 95% of participants found saliva and swab collection procedures acceptable.
CONCLUSIONS: Both saliva and swabs were highly sensitive and specific for culture-confirmed pulmonary TB. Saliva sensitivity exceeded the World Health Organization's ≥80% target for a low-complexity, nonsputum TB diagnostic test.