Effectiveness of inhaled hypertonic saline application for sputum induction to improve Mycobacterium tuberculosis identification in patients with pulmonary tuberculosis

Abstract

Background: This study assessed the effectiveness and diagnostic significance of hypertonic saline sputum induction for improving Mycobacterium tuberculosis (MTB) detection.

Methods: A prospective, randomized, open, two-arm, comparative study on MTB identification effectiveness when using inhaled sodium chloride hypertonic solution was performed in patients diagnosed with pulmonary tuberculosis (TB). Patients were randomly assigned into two groups: group 1 (inhalation group) included patients who inhaled a 7% sodium chloride solution upon admission to the hospital, and group 2 (control group) coughed up their sputum as usual. For both groups, specimens were tested by bacterioscopic, bacteriological, and molecular genetic methods. Diagnostic chest radiography was performed for all participants.

Results: In this study, 644 patients (mean age 42.2 years; 151 women, 23.4%) were randomly divided into two groups. Low-quality sputum samples were observed in 7.4% of patients from the inhalation group and 28.8% in the control group (p < 0.001). Acid-fast bacilli (AFB) smear was positive in 65.1% of patients from the inhalation group and 51.3% of controls (p = 0.002). A similar statistically significant situation was observed when culture methods (93.9% inhalation group and 81.9% control group, p < 0.001) and molecular genetic tests (92.2% inhalation group and 79.4% control group, p < 0.001) were used. Thus, active pulmonary TB was not verified microbiologically in 6.1% of patients from the inhalation group and in 18.1% of controls (p < 0.001).

Conclusions: Hypertonic saline sputum induction improves the quality of collected samples. This method may be appropriate to increase the rate of MTB detection in sputum using microscopic, bacteriological, and molecular genetic methods for diagnosing TB on the day of specimen collection. Hypertonic saline sputum induction is suitable for middle- and low-income countries with limited resources and causes no severe adverse effects in TB patients.

Keywords: Acid-fast bacilli; Developing countries; Diagnosis; Sodium chloride; Ziehl-Neelsen stain.