Assessment of diagnostic value of different methods (culture, PCR and biopsy) for the diagnosis of tuberculosis in patients with bronchial anthracosis

Introduction: Although several studies have shown the relationship between tuberculosis (TB) and anthracosis, few studies have investigated the diagnostic value of various methods of diagnosis of TB in these patients. Objectives: This study was conducted to investigate the diagnostic value of different methods including smear, culture and polymerase chain reaction (PCR) of bronchoalveolar lavage (BAL) sample and bronchial biopsy specimens in the diagnosis of TB in patients with bronchial anthracosis. Patients and Methods: This descriptive cross-sectional study was performed on 67 patients referring for bronchoscopy, and bronchial anthracosis was an incidental finding. The BAL sample and patients' bronchial biopsies were examined for TB infection. Results: The most affected areas by anthracosis were the right and the left upper lobes. The BAL smear and its culture were positive in 12 (20%) and 10 patients (17%), respectively. The PCR of BAL sample was positive in 37%. Non-specific chronic inflammation followed by bronchial anthracosis was the most common pathologic findings. According to pathological examinations, nine patients (13%) had TB. Sensitivity and specificity of the PCR versus culture were 90% and 70%, respectively, with a diagnostic accuracy of 74%. Sensitivity, specificity and diagnostic accuracy of the pathologic examination of biopsy specimen were 33%, 85% and 74%, respectively. Conclusion: Findings of this study showed that nearly one fifth of patients with bronchial anthracosis suffer from TB simultaneously. In these patients, PCR of the BAL and pathologic examination of the biopsy specimen had the same diagnostic accuracy, but the sensitivity of PCR was three times higher. However, application of PCR and pathologic examination does not seem to have more diagnostic advantages than BAL culture for the diagnosis of TB, although the results by PCR may help to diagnose the disease sooner.