Validity of symptoms and radiographic features in predicting positive acid-fast bacilli smears in adolescents with tuberculosis

SETTING: A cohort of 78 adolescents was selected for evaluation with culture or histologically proven pulmonary tuberculosis (PTB) from a tertiary paediatric facility in northern Taiwan. OBJECTIVE: To assess the validity of clinical features and radiographic findings for predicting positive smears of acid-fast bacilli (AFB) in adolescents with PTB. DESIGN: A retrospective descriptive study of adolescents with a confirmed diagnosis of PTB. Clinical symptoms and chest radiographs were assessed. Univariate analysis identified risk factors suggestive of a positive AFB smear, and the adjusted odds ratio (aOR) for these features was calculated using logistic regression. RESULTS: Patients who were AFB smear-positive and those who were smear-negative differed significantly on univariate analysis (P < 0.05) with respect to chronic cough, haemoptysis, multilobar or superior segment of lower lobe involvement, cavitations or presence of pleural effusions. Logistic regression analysis revealed that risk factors of positive smear in adolescents with PTB were chronic cough >4 weeks (aOR 13.8, 95%CI 2.3-83.1), lower lobe involvement (aOR 12.6, 95%CI 1.2-134.8) and pulmonary cavitations (aOR 7.7, 95%CI 1.0-57.7). CONCLUSIONS: For adolescents with PTB, those suffering from chronic cough for >4 weeks, with involvement of the superior segment of the lower lobe or with cavitary lesions, have a greater likelihood of transmitting tuberculosis due to smear positivity.