Diagnostic Accuracy of High-Resolution Computed Tomography of Chest in Diagnosing Sputum Smear Positive and Sputum Smear Negative Pulmonary Tuberculosis

Introduction Pulmonary tuberculosis (PTB) is caused by species of organisms in the Mycobacterium tuberculosis complex. It is a major public health problem worldwide and is endemic in Pakistan. Various clinical and biochemical markers exist for its diagnosis. Radiology has an important role in the diagnosis of PTB. Initially, a chest radiograph is warranted for PTB evaluation. High-resolution computed tomography (HRCT) also has high sensitivity and specificity for PTB diagnosis. Features of primary TB include consolidation, lymphadenopathy, pleural effusion and miliary nodules whereas post-primary TB include apical consolidation, nodules and cavitation. The aim of this study was to determine the diagnostic accuracy of HRCT chest in diagnosing sputum smear positive and smear negative PTB. Methods A cross-sectional study was conducted at a large tertiary care teaching hospital. A retrospective review of medical records of patients who underwent HRCT chest and sputum acid-fast bacillus (AFB) direct smear and AFB culture for suspicion of PTB was undertaken. All HRCT chest examinations were performed on multislice computed tomography (CT) scanner. On HRCT, PTB was defined as the presence of consolidation, centrilobular nodules, branching nodules with tree in bud appearance with or without lymphadenopathy and pleural effusion. Diagnostic accuracy of HRCT including sensitivity, specificity, positive and negative predictive values was calculated using 2 x 2 table, taking findings of AFB culture as a gold standard. Results A total of 108 patients were included in this study with a mean age of 51.85 ± 16.86 years. Diagnostic accuracy of HRCT in diagnosing PTB was found to be 84.26% with sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 89.09%, 79.25%, 81.67%, and 87.50%, respectively. In sputum smear positive patients, HRCT has diagnostic accuracy, sensitivity, specificity, PPV and NPV of 87.50%, 88.57%, 84.62%, 93.94%, and 73.33%, respectively. In sputum smear negative patients, HRCT has diagnostic accuracy, sensitivity, specificity, PPV and NPV of 81.67%, 90.00%, 77.50%, 66.67%, and 93.94%, respectively. Conclusion HRCT has high sensitivity in diagnosing sputum smear positive and sputum smear negative PTB. The specificity of HRCT in diagnosing sputum smear positive PTB was high, whereas it was slightly low in diagnosing sputum smear negative PTB. Overall diagnostic accuracy of HRCT was high in diagnosing PTB.