The Considerable, Often Neglected, Impact of Pulmonary Tuberculosis on the Prevalence of COPD

Abstract

In the executive summary of the 2006 update of the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines (1) the authors state that it is difficult to differentiate between chronic obstructive pulmonary disease (COPD) and pulmonary tuberculosis (TB) in some subjects due to similar respiratory symptoms and chronic airflow limitation and they suggest that a possible diagnosis of pulmonary TB should be considered in developing countries where these two diseases are common. Such comments focusing only on overlapping respiratory symptoms are adequate but not enough for the clinician in TB endemic areas. Treated pulmonary TB is a significant cause of obstructive airway disease with an inverse relationship between FEV1 and the extent of the disease on the original chest radiograph (2). Moreover this relationship is valid even with minimal involvement without cavitations on chest radiograph at presentation. Chronic bronchitis or bronchiolitis and emphysema often occur as complications of pulmonary TB. Additional exposure to cigarette smoke and other environmental risk factors leads to an increase in such occurrences. This was emphasized in the GOLD Workshop summary published in 2001 (3). Interestingly the degree of obstructive airway changes in subjects treated for TB increases with age the number of cigarettes smoked and the extent of the initial TB disease (4). In a study performed by our group (5) the impact of pulmonary TB on the prevalence of COPD was assessed. Even minimal scar change on chest radiograph without destroyed lung was associated with chronic airflow limitation. This was true in all subjects regardless of previous treatment history for TB. The prevalence of COPD increased from 3.7 to 5.0% by including participants with radiographically minimal previous TB lesions or past history of TB treatment. This substantially significant increase might act as a confounding factor and contribute to the prevalence of COPD in pulmonary TB endemic areas. The diagnosis of COPD recommended by GOLD is still based on the degree of airflow limitation assessed by spirometry. With respect to the epidemiology of COPD in pulmonary TB endemic areas further studies with careful consideration of subjects with minimal scar change on chest radiograph and/or previous history of pulmonary TB treatment are required to assess the impact of pulmonary TB on the prevalence of COPD. Conflict of Interest Statement: None of the authors has a financial relationship with a commercial entity that has an interest in the subject of this manuscript. (full-text)