Assessment of the role of high resolution computed tomography in the diagnosis of suspected sputum smear negative active pulmonary TB

ObjectiveThe aim of the present study is to study the utility of multi-detector CT chest in diagnosis of sputum smear negative pulmonary TB and correlation between the CT features and sputum culture results.Patients and methodsOne hundred patients suspected to have smear-negative active pulmonary TB were subjected to HRCT chest and sputum culture. At HRCT the combination of tree-in-bud, larger nodules, lobular consolidation and presence of main lesion in S1, S2 and S6 segments was ranked as rank 3 if at least three of them were present and as rank 2 if at least two of them were present. Patients with these findings mainly in the middle lobe and lingual were ranked as rank 1. The sensitivity, specificity and positive likelihood ratio for each rank was calculated.ResultsSputum culture for AFB was positive in 60 patients. At HRCT only six out of the 28 patients ranked as I and 24 out of the 40 ranked as II and 30 out of the 32 patients ranked as III had final diagnosis of active pulmonary TB. The sensitivity, specificity and positive likelihood ratio of rank I HRCT criteria for diagnosing active pulmonary TB was 90%, 50% and 1.5%, respectively, while in rank II it was 70%, 60%, 3.2%, respectively, and in rank III it was 50%, 95%, 12.5%, respectively.ConclusionHRCT chest findings can help to segregate higher risk patients among those suspected of having active pulmonary TB whose smears were negative. In addition HRCT can be used to select candidate patients for further laboratory tests or bronchoscopy.