Evaluation of the relationship between smear positivity and high-resolution CT findings in children with pulmonary tuberculosis

Background: The aim of this study is to find a relationship between the radiological manifestations of childhood tuberculosis on a high-resolution computed tomography (HRCT) and the results of sputum smear. This study aims to propose an alternative indicator of infectivity in terms of prevention of disease transmission through selective isolation policy in children whose clinical condition is highly suggestive of tuberculosis. Material and Methods: This retrospective comparative study was performed on 95 children under 15 years of age diagnosed with tuberculosis based on both WHO criteria and positive sputum culture for mycobacterium Tuberculosis. The children were admitted for TB screening in the pediatric department of national research institute of tuberculosis and lung disease (NRITLD) between 2008-2012. Direct smear collected from sputum or gastric lavage, as well as HRCT were performed in all children prior to administration of medical therapy. Children were divided into 2 groups based on positive and negative smear results. HRCT abnormalities, as well as their anatomical distribution were compared between these 2 groups using multivariate analytic model. Results: The most prevalent abnormalities in the positive smear group were consolidation, tree-in-bud pattern, upper lobe nodular infiltration and cavitation. The negative smear group featured lymphadenopathy, consolidation, collapse and nodular infiltration in the upper lobe. Cavity, tree- in-bud pattern and upper lobe nodular infiltration were highly associated with smear positivity in children. Conversely, lymphadenopathy and collapse had significant association with a negative smear. Conclusions: This study revealed that cavity, tree-in-bud and upper lobe nodular infiltration has significant association with smear positivity in childhood tuberculosis. On the other hand, lymphadenopathy and collapse were closely associated with smear negativity in this age group. It was also demonstrated that children with a positive smear most likely presented with radiological features of post primary tuberculosis, while the negative smear group most often manifested with primary tuberculosis.