BackgroundChitotriosidase is an accepted marker of macrophage activation. In this study, we investigated serum chitotriosidase levels in pulmonary tuberculosis (PTB).MethodsForth-two patients with PTB and 30 healthy subjects were enrolled in the study. The radiological extent of PTB, radiological sequela after treatment, and the degree of smear positivity were assessed. Chitotriosidase levels were measured by a fluorometric method.ResultsThe serum chitotriosidase levels of the PTB patients were significantly higher than those of the control subjects (39.73±24.97 vs. 9.63±4.55 nmol/mL/h, P<0.001). After completion of the standard 6-month antituberculous treatment, chitotriosidase levels in PTB patients significantly decreased (10.47±4.54 nmol/mL/h, P<0.001). Chitotriosidase levels correlated significantly with the radiological extent of PTB, degree of smear positivity, and post-treatment radiological sequela score (r=0.439, r=0.449, and r=0.337, respectively).ConclusionsThis study demonstrated that serum chitotriosidase levels increase in PTB; therefore, chitotriosidase can be used as a marker of disease activity, severity, and response to treatment.