Clinical Assessment of Unenhanced Chest CT as a Diagnostic Modality for Active Pulmonary Tuberculosis

Abstract

Background: Pulmonary tuberculosis (PTB) remains a major global health concern that requires early and accurate diagnosis. Standard methods, such as sputum smear microscopy and culture, are often slow and may miss smear-negative cases. Chest computed tomography (CT) can reveal radiologic features of active disease that are not detected by traditional tests. Objectives: The present study evaluated the diagnostic performance of unenhanced chest CT in identifying active PTB and its agreement with microbiological results. Methods: We conducted a cross-sectional diagnostic accuracy study at Bu-Ali-Sina Hospital, Zahedan, Iran, between March 2014 and November 2020. A total of 130 patients with suspected active PTB were enrolled. The CT findings were compared with culture and Bacillus Koch polymerase chain reaction (BK-PCR) results. Diagnostic indices, including sensitivity, specificity, predictive values, Youden’s Index, and likelihood ratios (LRs), were calculated by acid-fast bacilli (AFB) smear status. Statistical analysis was performed using SPSS 26.0, with significance set at P < 0.05. Results: The mean age of patients was 53 years, and 50.8% were male. Of the total, 85.4% were smear-positive (+1: 35.5%, +2: 32.3%, +3: 17.7%) and 14.6% were smear-negative. Common CT features included centrilobular nodules (61.5%), tree-in-bud pattern (49.2%), and cavitation (45.4%). Diagnostic accuracy varied by smear grade. For +2 AFB smears, CT achieved the best diagnostic balance (specificity 81.3%, sensitivity 47.4%; P = 0.02). In smear-negative patients, sensitivity was highest (86.7%) but specificity was low (25%; P = 0.57). A significant association was found between hallmark CT findings and microbiological confirmation (P = 0.01, LR > 1). Conclusions: Unenhanced chest CT adds diagnostic value in PTB, especially in patients with inconclusive smear or culture results. Incorporating CT into diagnostic pathways may improve early detection and clinical outcomes. Further multicenter studies are needed to validate its role in routine practice.