BACKGROUND: Nitric oxide (NO), a key macrophage antimycobacterial mediator that 
ameliorates immunopathology, is measurable in exhaled breath in individuals with 
pulmonary tuberculosis. We investigated relationships between fractional exhale 
NO (FENO) and initial pulmonary tuberculosis severity, change during treatment, 
and relationship with conversion of sputum culture to negative at 2 months.
METHODS: In Papua, we measured FENO in patients with pulmonary tuberculosis at 
baseline and serially over 6 months and once in healthy controls. Treatment 
outcomes were conversion of sputum culture results at 2 months and time to 
conversion of sputum microscopy results.
RESULTS: Among 200 patients with pulmonary tuberculosis and 88 controls, FENO 
was lower for patients with pulmonary tuberculosis at diagnosis (geometric mean 
FENO, 12.7 parts per billion [ppb]; 95% confidence interval [CI], 11.6-13.8) 
than for controls (geometric mean FENO, 16.6 ppb; 95% CI, 14.2-19.5; P = .002), 
fell further after treatment initiation (nadir at 1 week), and then recovered by 
6 months (P = .03). Lower FENO was associated with more-severe tuberculosis 
disease, with FENO directly proportional to weight (P < .001) and forced 
vital-capacity (P = .001) and inversely proportional to radiological score (P = 
.03). People whose FENO increased or remained unchanged by 2 months were 
2.7-fold more likely to achieve conversion of sputum culture than those whose 
FENO decreased (odds ratio, 2.72; 95% CI, 1.05-7.12; P = .04).
CONCLUSIONS: Among patients with pulmonary tuberculosis, impaired pulmonary NO 
bioavailability is associated with more-severe disease and delayed mycobacterial 
clearance. Measures to increase pulmonary NO warrant investigation as adjunctive 
tuberculosis treatments.