The effectiveness of sputum pH analysis in the prediction of response to therapy in patients with pulmonary tuberculosis

• Published in: PeerJ (San Francisco, CA) Vol. 3; p. e1448
• Main Authors: Masuda, Makoto, Sato, Takashi, Sakamaki, Kentaro, Kudo, Makoto, Kaneko, Takeshi, Ishigatsubo, Yoshiaki
• Format: Journal Article
• Language: English
• Published: United States PeerJ. Ltd 26.11.2015; PeerJ, Inc; PeerJ Inc
• Subjects: Acidity; Acids; Age; Airway acidity; Analysis; Antituberculous therapy; Asthma; Bactericidal activity; Care and treatment; Cavitation; Chronic obstructive pulmonary disease; Drug resistance; Epidemiology; Ethambutol; Immunology; Infectious Diseases; Isoniazid; Lungs; Medicine; Microscopy; Multivariate analysis; Mycobacterium tuberculosis; Patients; pH effects; Public Health; Pulmonary tuberculosis; Pyrazinamide; Respiratory Medicine; Respiratory tract; Rifampin; Sputum; Sputum pH; Studies; Tuberculosis; University graduates; Japan; Airway acidity; Antituberculous therapy; Sputum pH; Pulmonary tuberculosis
• ISSN: 2167-8359; 2167-8359
• DOI: 10.7717/peerj.1448

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.