Pulmonary tuberculosis (PTB) remains a major global health burden, particularly in low- and middle-income countries, despite significant advances in diagnosis and therapy. According to the World Health Organization’s Global Tuberculosis Report 2023, an estimated 10.6 million people fell ill with TB in 2022, with India contributing the highest number of cases globally [1]. Although effective anti-tubercular therapy leads to microbiological cure, a substantial proportion of individuals continue to experience chronic respiratory symptoms and functional impairment due to residual structural lung damage.

Chronic pulmonary sequelae following tuberculosis include bronchiectasis, fibrosis, cavitary lesions, and airway distortion, all of which may significantly compromise lung function [2]. These post-tuberculosis pulmonary changes are increasingly being recognized as a distinct clinical entity known as post-tuberculosis lung disease (PTLD), characterized by persistent symptoms and irreversible physiological deficits long after bacteriological cure [3].

Pulmonary function tests (PFTs), especially spirometry, serve as valuable tools to quantify the extent and pattern of respiratory impairment in such patients. Previous studies have demonstrated a high prevalence of abnormal spirometric patterns in treated PTB cases, ranging from obstructive and restrictive to mixed ventilatory defects [4,5]. Smoking, duration of illness, and extent of radiological involvement have been identified as key determinants of functional outcome.

Despite these observations, routine assessment of pulmonary function in post-TB patients is often overlooked in clinical practice. This study was therefore undertaken to evaluate spirometric parameters in patients with chronic pulmonary tuberculosis and to identify common patterns of pulmonary dysfunction, with the goal of supporting evidence-based rehabilitation strategies.

Study Design and Setting:

This hospital-based, observational study was conducted in the Department of Pulmonology at Nimra Institute of Medical Sciences, Vijayawada, Andhra Pradesh, over six months from June  2024 to November  2024.

Study Population:

A total of 100 adult patients with a prior confirmed diagnosis of pulmonary tuberculosis were enrolled. All patients had completed a full course of anti-tubercular therapy at least six months before recruitment and were attending the outpatient or inpatient services for persistent respiratory symptoms or follow-up.

 Inclusion Criteria:

Age ≥ 18 years

Microbiologically or radiologically confirmed history of pulmonary tuberculosis

Completion of anti-tubercular treatment ≥ 6 months prior to enrolment

Ability to perform spirometry reliably

 Exclusion Criteria:

Active tuberculosis or ongoing anti-tubercular treatment

Known history of chronic obstructive pulmonary disease, asthma, or interstitial lung disease unrelated to TB Acute respiratory infection in the last four weeks Inability to perform spirometry due to physical or cognitive limitations

 Data Collection:

Demographic details, smoking history, and duration since TB diagnosis were recorded using a structured proforma. Each participant underwent a detailed clinical evaluation followed by spirometry, performed using a calibrated portable spirometer according to American Thoracic Society (ATS) guidelines. Parameters measured included Forced Expiratory Volume in one second (FEV₁), Forced Vital Capacity (FVC), FEV₁/FVC ratio, and Peak Expiratory Flow Rate (PEFR).

Classification of Spirometric Patterns:

 Obstructive: FEV₁/FVC < 70% with reduced FEV₁

 Restrictive: FVC < 80% predicted with normal or high FEV₁/FVC

 Mixed: Both FEV₁/FVC < 70% and FVC < 80% predicted

 Normal: All parameters within predicted normal range

 Statistical Analysis:

Data were entered into Microsoft Excel and analyzed using SPSS version 26.0. Descriptive statistics were used for baseline variables. Frequencies and percentages were calculated for categorical variables, while means and standard deviations were reported for continuous variables. Associations between spirometric patterns and smoking status were evaluated using the Chi-square test, with p < 0.05 considered statistically significant.

 Ethical Considerations:
The study was conducted after obtaining approval from the Institutional Ethics Committee of Nimra Medical College. Written informed consent was obtained from all participants prior to enrolment, and confidentiality of data was strictly maintained.

A total of 100 patients with a confirmed diagnosis of chronic pulmonary tuberculosis were included in the study. The mean age of the participants was 45.3 ± 12.6 years, and males constituted a majority (67%). A substantial proportion (42%) were either current or former smokers, while the remainder (58%) were non-smokers (Table 1).

Table 1: Demographic and Baseline Characteristics of Study Participants (N = 100)

Analysis of spirometric patterns revealed that only 14% of participants had normal pulmonary function. The most prevalent abnormal pattern was obstructive (38%), followed by restrictive (29%) and mixed (19%) ventilatory defects (Table 2). This distribution indicates that the majority of patients exhibited some form of pulmonary impairment.

Table 2: Distribution of Spirometric Patterns

Figure 1.Distribution of Spirometric Patterns

The mean forced expiratory volume in one second (FEV₁) was 1.72 ± 0.54 L, corresponding to 61.8 ± 12.4% of the predicted value. The mean forced vital capacity (FVC) was 2.21 ± 0.62 L (68.3 ± 13.2% predicted), and the FEV₁/FVC ratio was reduced to an average of 63.1 ± 9.8%, suggesting airflow limitation in a significant proportion. Peak expiratory flow rate (PEFR) was also notably diminished, with a mean value of 278.4 ± 82.5 L/min (Table 3).

Table 3: Pulmonary Function Parameters (Mean ± SD and % Predicted)

Figure 2.Pulmonary Function Parameters

When stratified by smoking status, the obstructive pattern was predominantly observed in smokers (24 out of 42), whereas the restrictive pattern was more common among non-smokers (22 out of 58). Mixed ventilatory defects were relatively evenly distributed, though slightly more frequent in non-smokers. Normal spirometry was identified in only a small subset of both groups (Table 4).

Table 4: Association Between Spirometric Pattern and Smoking Status

Figure 3.Association Between Spirometric Pattern and Smoking Statu

The present study underscores the substantial burden of pulmonary function impairment among individuals previously treated for chronic pulmonary tuberculosis. A striking 86% of our cohort exhibited abnormal spirometric patterns, predominantly obstructive (38%) and restrictive (29%), which aligns with emerging literature recognizing post-tuberculosis lung disease (PTLD) as a significant sequela of TB.

Our findings are consistent with those of Zhao et al. (2024), who demonstrated distinct patterns of lung function impairment in tuberculosis-destroyed lung (TDL) patients, with obstructive defects being most frequent, particularly in those with cavitary lesions and smoking history [6]. Ivanova et al. (2023), in a large-scale meta-analysis of 14,621 patients, reported a pooled prevalence of impaired spirometry in over 60% of post-TB cases, further supporting the global relevance of our results [7].

Notably, the predominance of obstructive ventilatory defects among smokers in our study suggests a synergistic impact of tuberculosis and tobacco exposure on airway remodeling and chronic inflammation. This relationship is substantiated by Fan et al. (2021), who confirmed through meta-analysis that previous TB infection significantly increases the risk of developing chronic obstructive pulmonary disease (COPD), independent of smoking status [8].

In adolescents, van der Zalm et al. (2024) demonstrated that impaired lung function may manifest during TB treatment and persist well into post-treatment follow-up, highlighting the long-term nature of functional compromise irrespective of age [9]. In the Indian context, Santra et al. (2017) identified a high burden of post-tuberculous obstructive airway disease, especially in patients with fibrotic changes and emphysematous destruction [10], which resonates with our findings in non-smoking individuals with restrictive and mixed defects.

Despite increasing awareness of PTLD, its management remains under-addressed in routine clinical care. Seo et al. (2024) emphasized the need for structured, long-term strategies including pulmonary rehabilitation, inhaled therapy, and regular spirometric monitoring to mitigate the burden of PTLD [11]. Furthermore, Jiang et al. (2024) have initiated a prospective multicenter study in China to characterize TB-associated COPD, aiming to develop individualized treatment frameworks that may inform future guidelines [12].

Taken together, these findings reinforce the urgency of incorporating routine pulmonary function testing in post-TB care pathways. Identifying early ventilatory defects allows for timely interventions that may significantly improve respiratory health and quality of life in this vulnerable population.

This study was limited by its single-center design and lack of radiological correlation. Longitudinal follow-up would provide further insight into progression or stabilization of spirometric abnormalities over time.

This hospital-based observational study underscores the high prevalence of pulmonary function abnormalities among patients with chronic pulmonary tuberculosis, even after successful completion of anti-tubercular therapy. Obstructive, restrictive, and mixed ventilatory defects were frequently observed, with a significant association between smoking and obstructive patterns. These findings highlight the irreversible nature of post-tuberculosis lung damage and the need for long-term respiratory follow-up. Routine spirometry should be incorporated into post-treatment care to identify functional impairments early and guide rehabilitative interventions. Integrating pulmonary rehabilitation, smoking cessation programs, and periodic monitoring may significantly improve quality of life and functional outcomes in this vulnerable patient population.

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