title: The effectiveness of sputum pH analysis in the prediction of response to therapy in patients with pulmonary tuberculosis.
abstract: Purpose. The predictive factor of response to antituberculous therapy has not been fully elucidated. Airway acidity has been thought to be a potential indicator of the bactericidal activity. Therefore, we hypothesized that monitoring airway acidity by measuring sputum pH could predict response to therapy. Methods. A total of 47 patients having newly diagnosed, smear-positive, active pulmonary tuberculosis were enrolled between October 2011 and March 2014. Sputum samples were serially analyzed before and after treatment. Eligible patients who initiated a standard 6-month treatment were monitored for the length of time to sputum smear and culture conversion. Results. There were 39 patients who completed a 2-month intensive phase of isoniazid, rifampicin, pyrazinamide, and ethambutol therapy followed by a 4-month continuation phase of isoniazid and rifampicin. Although factors including age, cavitation, sputum grade, and use of an acid-suppressant were associated with initial low sputum pH in univariate analysis, multivariate analysis revealed that only age ≥61 years was a statistically important factor predicting low pH value (p = 0.005). Further outcome analysis showed that initial low sputum pH before treatment was the only factor significantly associated with shorter length of time to both sputum smear and culture conversion (p = 0.034 and 0.019, respectively) independent of the effects of age, sputum bacterial load, extent of lung lesion, and cavitation. Thus, initial low sputum pH indicated favorable response to anti-tuberculosis therapy. Conclusions. Measuring sputum pH is an easy and inexpensive way of predicting response to standard combination therapy in patients with pulmonary tuberculosis.
authors.affiliation: Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine , Yokohama , Japan ; Department of Pulmonology, Yokohama City University Graduate School of Medicine , Yokohama , Japan ; Department of Respiratory Medicine, Fujisawa City Hospital , Fujisawa , Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Masuda
authors.affiliation: Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine , Yokohama , Japan ; Department of Pulmonology, Yokohama City University Graduate School of Medicine , Yokohama , Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Sato
authors.affiliation: Department of Biostatistics and Epidemiology, Yokohama City University Graduate School of Medicine , Yokohama , Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Sakamaki
authors.affiliation: Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine , Yokohama , Japan ; Department of Pulmonology, Yokohama City University Graduate School of Medicine , Yokohama , Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Kudo
authors.affiliation: Department of Pulmonology, Yokohama City University Graduate School of Medicine , Yokohama , Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kaneko
authors.affiliation: Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine , Yokohama , Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Ishigatsubo
keywords: Airway acidity; Antituberculous therapy; Pulmonary tuberculosis; Sputum pH