Correlation of microbiological yield with radiographic activity on chest computed tomography in cases of suspected pulmonary tuberculosis

BACKGROUND: Little is known about the correlation between microbiological yield and radiographic activity, on chest computed tomography (CT), in suspected pulmonary tuberculosis (PTB) cases, despite CT being widely used, clinically. METHODS: We used multicenter retrospective data, obtained from medical records, focusing on the diagnostic performance for definite PTB. We categorized patients into four groups, by radiographic activity: definitely active, probably active, indeterminate activity, and probably inactive. RESULTS: Of the 650 patients included, 316 had culture-confirmed PTB; 190 (29.2%), 323 (49.7%), 70 (10.8%), and 67 (10.3%) were classified into the definitely active, probably active, indeterminate activity, and probably inactive groups, respectively. The corresponding observed culture rates for CT radiographic activity were 61.6%, 60.7%, 4.3% and 0%, respectively. When not only culture rates but TB-PCR and histological results were taken into consideration as definite PTB, it showed 66.6%, 67.2%, 14.3%, and 0% of each CT radiographic activity, respectively. Regarding the diagnostic performance for definite PTB, radiographic activity displayed high sensitivity (97.1%, 95% confidence interval (CI), 94.6–98.5) and negative predictive values (92.7%, 95% CI, 86.6–96.2), considered definitely and probably active PTB. Apart from PTB, other etiologies, according to radiographic activity, were predominantly respiratory infections such as bacterial pneumonia and non-tuberculous mycobacterial infection. CONCLUSIONS: Radiographic activity showed good diagnostic performance, and can be used easily in clinical practice. However, clinicians should consider other possibilities, because radiologic images do not confirm microbiological PTB.