New onset adult asthma attributable to tuberculosis: A distinct phenotype?

Abstract Background: In clinical practice, we encounter cases of bronchial asthma the onset of which correlates with past tuberculosis (TB), either pulmonary or extrapulmonary. Our study attempts to validate this observation and assess likelihood of new asthma that is attributable to TB. Methods: It was a single visit, cross-sectional study of persons who had TB within last 5 years (group 1). Preexisting asthma before TB, COPD cases, smokers, and persons with any active infective or diffuse lung diseases were excluded. Their spouse (group 2) and first-degree relatives (group 3) served as controls. All participants were subjected to detailed history, examination, and spirometry. Sample size was 225 (75 in each group). Results: About 62/75 participants in group 1 had intermittent or persistent symptoms suggesting obstructive airway disease that started within a year of TB diagnosis. Obstructive spirometry pattern was observed in 23/75 (30.6%) post-TB cases, compared to 6/75 (8%) in group 2 and 4/75 (5.33%) in group 3 participants. While, 11/75 (14.66%) post-TB cases in comparison to 7/150 (4.66%) controls were diagnosed as asthma after clinical correlation. About 24% of persons with post-TB lung scarring, 16% without lung scarring, and 4% with only extrapulmonary TB were diagnosed as asthma. Attributable risk for post-TB asthma was significant (0.1). Conclusion: This study suggests causative association between TB and asthma rather than just comorbidity. Further large-scale studies are warranted.