Post-tuberculosis (TB) patients have a high prevalence of airway obstruction and small airway dysfunction compared to those who are not post-TB, suggests a study published in the March 2023 issue of the journal Thorax.¹

To examine the effect of post-TB on lung function, researchers selected 8680 patients with a mean age of 40.1 years. Half of them were women (50.8%). The study further aimed to describe general characteristics and chronic respiratory symptoms of people with post-TB, which was diagnosed based on the history and/or x-ray findings of “linear or reticular fibrotic scars or dense nodules with distinct margins, with or without calcifications, within the upper lobes”.

Post-TB was detected in 610 (7.0%) of the 8680 study subjects included in the study; 463 (5.3%) had evidence of post-TB on chest x-ray; just 98 (1.1%) gave a history of TB. Forty-nine patients (0.6%) had both – a positive chest x-ray as well as a self-reported history of TB. Post-TB patients tended to be male, older in age, city dwellers, have more comorbid conditions such as asthma, diabetes, dyslipidemia and lower oxygen saturation (SpO2). Their educational status was also inferior. Out of the 610 post-TB patients, 33.6% were ever smokers, while 66.4% were never smokers.

Respiratory symptoms such as chronic cough, sputum, dyspnea and recurrent wheezing occurred more often in the post-TB patients (46.8%) compared to those who showed no evidence of post-TB (28.3%). The probability of airflow obstruction was found to be higher among the post-TB patients (21.3% vs 15.2%) with odds ratio of 1.31 after adjustment for other confounding variables. Nearly half of the post-TB patients (48.9% vs 37.5%) were also found to have small airway dysfunction with OR of 1.28.

In a subgroup analysis, post-TB never smoker patients were also at higher risk of airflow obstruction (OR 1.37) and small airway dysfunction (OR 1.47).

On spirometry, compared to patients without post-TB, post-TB patients had lower post-bronchodilator values for FEV1/FVC% (78.4 vs 82.4), FVC (3.57 vs 3.73) and FEV1 (2.80 vs 3.07) and lower (less than 65% of predicted) maximal mid-expiratory flow (MMEF), forced expiratory flow (FEF) 50% and FEF 75% values.

These findings demonstrate a high prevalence of post-TB along with a positive association of post-TB status with impairment of lung function and chronic respiratory symptoms compared to non-post-TB patients. Nearly half of the population in this study had impaired pulmonary function and more frequent respiratory symptoms, which may negatively affect quality of life. Never-smoker post-TB subjects also had higher association with airflow obstruction suggesting post-TB as a significant cause for obstructive lung disease in this group of patients.

This study highlights the importance of not only treating TB, but also mitigating its long-term effects on lung function and respiratory symptoms by close monitoring of the patient, especially in countries with high burden of TB such as ours.

Reference

1. Xing Z, et al. Airflow obstruction and small airway dysfunction following pulmonary tuberculosis: a cross-sectional survey. Thorax. 2023 Mar;78(3):274-280. doi: 10.1136/thoraxjnl-2021-218345.