Spontaneous and induced sputum values in the diagnosis of pulmonary tuberculosis among patients with suspected pulmonary tuberculosis

Objectives: The quality of sputum samples is important for the diagnosis of pulmonary tuberculosis (TB). Unfortunately, it is not always possible to get a proper sputum sample. Now, sputum induction (SI) has been found to be useful for the diagnosis of many lung diseases. Therefore, this study compares the role of spontaneous sputum and induced sputum in the diagnosis of pulmonary TB among suspected pulmonary TB patients. Materials and Methods: A total of 27 patients admitted with suspected pulmonary TB were studied. Three spontaneous sputum samples were taken from these patients and in case of negative sputum smear microscopy, the SI procedure was used to take another sputum sample. Standard diagnosis included both positive sputum smear and clinical decisions. The sensitivity, specificity, and positive and negative predictive values of sputum smears obtained by two methods of spontaneous sputum and induced sputum were calculated and compared with the standard diagnosis. Results: The result of the induced sputum acid-fast bacillus (AFB) smear microscopy was negative in 16 (59.3%) patients and positive in 11 (40.7%) patients. Six (50%) of those who were negative in spontaneous sputum became positive after SI. The mean white blood cell (WBC) count in normal sputum and induced sputum was 3.8 (±3.4) and 8.8 (±2.9), respectively (P < 0.001). The sensitivity of sputum smear positive was calculated to be 67.7% for SI method and 29.4% for spontaneous sputum method. Conclusion: The diagnostic value of induced sputum in the diagnosis of TB is more than the spontaneous sputum method. In addition, the quality of sputum smear produced through induction is more than spontaneous sputum and it does not create any special complication.