High Resolution Computed Tomography in the Diagnosis of Pulmonary Tuberculosis and its Correlation with Sputum/ Bronchoalveolar Lavage Analysis

Abstract

Introduction: Pulmonary Tuberculosis (PTB) is one of the major health related burden in the entire country. Clinicians face dilemma whether to start antitubercular treatment or not in sputum negative patients. In equivocal or negative microbiological results High Resolution Computed Tomography (HRCT) can be helpful tool to guide physicians whether or not to start the treatment in patients with suspicion of active PTB. Aim: To assess the accuracy of HRCT in diagnosis and evaluation of disease activity in PTB and to correlate the findings of HRCT with Acid-Fast Bacilli (AFB) smear & culture results. Materials and Methods: An observational study was conducted between August 2015 to August 2017, in which fifty patients with suspected PTB were included into the study. HRCT thorax and Sputum/Bronchoalveolar Lavage (BAL) AFB smear & culture tests were performed for each of these patients. The pattern, extent and severity of HRCT features were assessed and results correlated with sputum/BAL AFB findings. Active tuberculosis was confirmed when smear and/or culture of AFB in sputum or lavage fluid are positive and/or when follow-up HRCT showed radiological improvement with antituberculous chemotherapy. The statistical tests were applied and analysed using appropriate statistical software Statisitcal Package for Social Sciences (SPSS) version 16. The chi square test was used to determine the association and p-value <0.05 was considered to be significant. A p-value <0.05 was considered statistically significant. Results: Mean age was 36.3±3.18 years. The most frequent CT patterns of active disease, present as isolated or mixed findings, were centrilobular nodules (73%), tree-in-bud opacities (59%) and larger nodules (54%). Distribution of the HRCT findings was noted to be more common in apical segments of upper lobes and superior segments of lower lobes. High Resolution CT showed high diagnostic accuracy (94%). Active (35/37, 94.5%) and inactive (12/13, 92.3%) state could be correctly differentiated by HRCT. Sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) HRCT were calculated to be 97.22%, 85.71%, 94.59% and 92.31%. Conclusion: This study concludes that HRCT is a powerful and reliable investigation in the diagnosis of tuberculosis and determination of it’s disease activity, when other means of diagnosis such as sputum/BAL AFB test and Culture fail to settle the matter, are not available or time consuming and should be routinely indicated in sputum smear negative patients for prompt initiation of antitubercular treatment.

Keywords

• afb
• culture
• disease activity
• radiology
• smear