Obstructive pulmonary disease in patients with previous tuberculosis: Pathophysiology of a community-based cohort

Abstract

Background. An association between chronic airflow limitation (CAL) and a history of pulmonary tuberculosis (PTB) has been confirmed in epidemiological studies, but the mechanisms responsible for this association are unclear. It is debated whether CAL in this context should be viewed as chronic obstructive pulmonary disease (COPD) or a separate phenotype. Objective. To compare lung physiology and high-resolution computed tomography (HRCT) findings in subjects with CAL and evidence of previous (healed) PTB with those in subjects with smoking-related COPD without evidence of previous PTB. Methods. Subjects with CAL identified during a Burden of Obstructive Lung Disease (BOLD) study performed in South Africa were studied. Investigations included questionnaires, lung physiology (spirometry, body plethysmography and diffusing capacity) and quantitative HRCT scans to assess bronchial anatomy and the presence of emphysema (<-950 HU), gas trapping (<-860 HU) and fibrosis (>-200 HU). Findings in subjects with a past history and/or HRCT evidence of PTB were compared with those in subjects without these features. Results. One hundred and seven of 196 eligible subjects (54.6%) were enrolled, 104 performed physiology tests and 94 had an HRCT scan. Based on history and HRCT findings, subjects were categorised as no previous PTB (NPTB, n=31), probable previous PTB (n=33) or definite previous PTB (DPTB, n=39). Subjects with DPTB had a lower diffusing capacity (Δ=-17.7%; p=0.001) and inspiratory capacity (Δ=-21.5%; p=0.001) than NPTB subjects, and higher gas-trapping and fibrosis but not emphysema scores (Δ=+6.2% (p=0.021), +0.36% (p=0.017) and +3.5% (p=0.098), respectively). Conclusions. The mechanisms of CAL associated with previous PTB appear to differ from those in the more common smoking-related COPD and warrant further study.

<p>Transition from Restrictive to Obstructive Lung Function Impairment During Treatment and Follow-Up of Active Tuberculosis</p>

“…11 The mechanisms responsible for the consistently observed finding of reduced DL CO is less clear, but potential involvement of vasculature within the bronchovascular bundle in and around small airways is one potential mechanism. 15 Several large multi-centre studies and systematic reviews have demonstrated the association of previous tuberculosis and spirometric abnormalities. [3][4][5][6]13,14,19,20 However, these and several smaller studies have been performed without the use of plethysmography or quantitative imaging.…”

“…In a previous observational study of patients with a past history of PTB and spirometric evidence of AFO, we have confirmed that static gas trapping and reduced diffusing capacity (DLco) are common findings, and we have hypothesized that this is best explained by widespread cicatricial changes in or surrounding bronchovascular bundles containing small airways. 15 Further, this process may progress over time and contribute to chronic airflow obstruction seen later after treatment has been completed. This observation raises the possibility of considering interventions that might limit these late effects of PTB.…”

Spirometry results after treatment for pulmonary tuberculosis: comparison between patients with and without previous lung disease: a multicenter study

“…Functional changes constitute knowledge gaps that warrant further studies, especially studies aimed at determining whether airway obstruction due to PTB is a different entity from COPD due to exposure to cigarette smoke or smoke from wood-burning stoves, silicosis, etc. (38) In addition, further studies could assess responses to treatments such as the use of specific inhaled medication and pulmonary rehabilitation to improve patient quality of life.…”

Five-year follow-up of participants diagnosed with chronic airflow obstruction in a South African Burden of Obstructive Lung Disease (BOLD) survey

“…The role of PTB in this cohort has been studied in greater detail and reported elsewhere. [16,17] In addition, in this over-40 age group, ~15% of participants may be considered to have asthma with evidence of CAO at the time of the original survey. However, the majority of patients in the current study best fit the description of COPD, namely CAO with a significant history of smoking or similar exposure, with no or minimal evidence of post-PTB scarring on a chest radiograph and lung computed tomography scan.…”