Tobacco smoking is a well-established risk factor for a wide spectrum of pulmonary diseases, including chronic obstructive pulmonary disease (COPD), lung cancer, interstitial lung disease (ILD), and emphysema. The majority of these pathologies remain clinically silent in early stages, and by the time symptoms emerge, considerable structural damage has often occurred. Early detection and accurate characterization of these abnormalities in symptomatic smokers is therefore critical for initiating timely interventions and improving prognosis [1]. Traditionally, chest radiography has been the initial imaging modality in symptomatic patients; however, its sensitivity in detecting early parenchymal and interstitial abnormalities is suboptimal. In contrast, high-resolution computed tomography (HRCT) offers superior anatomical resolution, allowing precise visualization of small airways, interstitial tissue, and early emphysematous changes [2]. The advancement of low-dose HRCT protocols has significantly mitigated concerns about radiation exposure, making it a practical tool for evaluating high-risk populations such as chronic smokers [3].

In symptomatic smokers—those presenting with persistent cough, breathlessness, or unexplained respiratory symptoms—the ability of low-dose HRCT to distinguish between diverse pulmonary conditions becomes particularly valuable. It facilitates differential diagnosis, guides targeted treatment strategies, and enables risk stratification, especially in resource-limited settings where full-dose CT may not be feasible or advisable [4]. Furthermore, recent studies have highlighted the clinical utility of HRCT in detecting subclinical findings such as early interstitial changes and centrilobular emphysema that are not evident on spirometry or plain radiographs [5].

Despite its established diagnostic advantages, HRCT has not been uniformly implemented in the routine evaluation of symptomatic smokers, partly due to the lack of population-specific data. In India, where smoking prevalence remains substantial and diagnostic delays are common, there is a growing need to integrate imaging-based screening into standard pulmonary care. However, data on HRCT utility among symptomatic smokers in this setting remain sparse [6].

This study was therefore designed to evaluate the spectrum of lung abnormalities detected by low-dose HRCT thorax in symptomatic smokers and to explore the association between clinical parameters and imaging findings. The goal is to identify imaging patterns that may suggest early or alternative diagnoses beyond clinical suspicion, thereby guiding more effective clinical management in this high-risk group.

This cross-sectional observational study was conducted in the Department of Radiodiagnosis at a tertiary care teaching hospital over a period of 12 months, from March 2024 to February 2025. The study aimed to assess HRCT thorax findings among smokers presenting with respiratory symptoms.

Inclusion Criteria

• Adults aged ≥35 years
• History of smoking ≥10 pack-years
• Presence of one or more respiratory symptoms (e.g., chronic cough, breathlessness, chest discomfort, wheezing)

Exclusion Criteria

• Known diagnosis of primary lung malignancy
• Recent pulmonary infections (within 4 weeks)
• History of prior thoracic surgery
• Pregnant or lactating women
• Inability to undergo CT scan due to contraindications

Data Collection and Imaging Protocol

After obtaining informed consent, demographic details, clinical history, and smoking index (pack-years) were recorded. Symptom duration was noted in months and converted to years. All participants underwent low-dose HRCT thorax using a 128-slice multidetector CT scanner. The protocol involved a non-contrast scan in full inspiration, with collimation set at 1 mm, reconstruction at 1.25 mm, and voltage parameters at 100–120 kVp using automated dose modulation.

HRCT findings were categorized as:

• Normal
• Emphysematous changes
• Bronchiectasis
• Interstitial lung disease
• Pulmonary nodules

Data were entered into Microsoft Excel and analyzed using SPSS version 26. Descriptive statistics were used for continuous variables (mean, SD, range), and categorical variables were expressed as frequencies and percentages. Group comparisons were done using Chi-square test or Fisher’s exact test for proportions, and ANOVA or independent t-test for continuous variables. A p-value of <0.05 was considered statistically significant.

The study protocol was approved by the Institutional Ethics Committee. Written informed consent was obtained from all participants prior to inclusion.

Table 1: Demographic Characteristics

Table 2: HRCT Findings Distribution

Table 3: Diagnosis Confirmation by HRCT Finding

Table 4: Symptom Duration by HRCT Finding

Table 5: Pack-Years by HRCT Finding

In this cross-sectional evaluation of 120 symptomatic smokers, 82 were male (68.3%) and 38 female (31.7%). The mean age among males was 52.9 years, while females averaged 55.9 years. Mean tobacco exposure, measured in pack-years, was slightly higher in females (20.6) compared to males (19.9), although both groups exhibited substantial cumulative risk.

High-resolution computed tomography (HRCT) identified emphysema as the most frequent pathology (49/120; 40.8%), followed by normal scans (31/120; 25.8%), bronchiectasis (21/120; 17.5%), interstitial lung disease (ILD) in 12 patients (10%), and nodules in 7 cases (5.8%). These frequencies are illustrated in the accompanying bar graph.

Diagnosis confirmation was highest for emphysema (43/49; 87.8%) and bronchiectasis (19/21; 90.5%). ILD also showed a high concordance (10/12; 83.3%). Conversely, nodules had a lower confirmation rate (4/7; 57.1%), and patients with normal HRCT findings had 25 confirmed diagnoses out of 31 cases (80.6%). Symptom duration differed across categories. Patients with nodules had the longest mean duration (5.43 years), followed by emphysema (4.16 years), bronchiectasis (3.88 years), and ILD (3.85 years). Those with normal HRCT had a slightly lower mean symptom duration (3.73 years), suggesting earlier or non-structural pathology.

Tobacco exposure varied by HRCT finding. The highest mean pack-years were observed in ILD (22.25), followed by emphysema (20.22), normal (20.13), bronchiectasis (19.52), and nodules (17.14). Notably, even those with normal HRCT findings had substantial exposure, indicating that structural abnormalities may lag behind clinical symptoms in smokers.

Tobacco smoking remains the most significant modifiable risk factor for chronic pulmonary diseases worldwide. Despite global anti-smoking campaigns, a considerable proportion of individuals continue to present with respiratory symptoms attributed to long-term smoking, particularly in low- and middle-income countries [7]. This study utilized low-dose high-resolution computed tomography (HRCT) to evaluate lung abnormalities in symptomatic smokers and revealed that 40.8% of patients had emphysema, 17.5% had bronchiectasis, 10% had interstitial lung disease (ILD), and 5.8% presented with pulmonary nodules.

Our results are consistent with those of Gould et al. [8], who reported emphysematous changes in 45% of long-term smokers with chronic respiratory symptoms using quantitative HRCT. Similarly, Lynch et al. [9] documented HRCT-detected ILD in approximately 9–11% of asymptomatic smokers with high pack-year exposure, closely aligning with our 10% ILD prevalence in symptomatic individuals. This supports the sensitivity of HRCT in detecting subclinical or early-stage lung pathology that might otherwise remain undiagnosed using conventional radiography.

Diagnosis confirmation was highest among patients with emphysema (87.8%) and bronchiectasis (90.5%), underscoring the high radiological-clinical concordance of HRCT in these diseases. These findings are supported by Bastos et al. [10], who emphasized the role of HRCT in diagnosing bronchiectasis, where radiological evidence often precedes clinical suspicion. The lower confirmation rate in nodular lesions (57.1%) in our study reflects diagnostic uncertainty and the necessity of follow-up imaging or tissue sampling to rule out neoplastic or inflammatory etiologies, as reinforced by similar observations in the NELSON lung cancer screening trial [11].

Interestingly, symptom duration did not always correlate linearly with disease severity. Patients with nodules had the longest mean symptom duration (5.43 years), possibly reflecting chronic inflammation or coexisting subclinical disease processes. ILD and bronchiectasis had symptom durations of 3.85 and 3.88 years respectively, similar to findings by Washko et al. [12], who noted that clinical symptoms often lag behind structural changes, especially in ILD.

Tobacco exposure, measured in pack-years, was highest in patients with ILD (mean 22.25), indicating a dose-response relationship between cumulative exposure and fibrotic pathology. This parallels the conclusions of Lederer et al. [13], who found that smoking not only increases the risk of emphysema but also contributes to fibrotic remodeling in predisposed individuals. Surprisingly, patients with normal HRCT findings had a mean of 20.13 pack-years, implying that functional deficits or early-stage disease may precede detectable structural changes.

This study demonstrates that low-dose HRCT thorax is a highly effective tool for early identification of diverse pulmonary abnormalities in symptomatic smokers. Given the high radiological yield, especially in those with moderate-to-high pack-year exposure, HRCT can guide timely intervention before irreversible damage ensues.

This study underscores the diagnostic utility of low-dose HRCT thorax in evaluating lung abnormalities among symptomatic smokers. Emphysema emerged as the predominant radiological finding, followed by bronchiectasis, ILD, and pulmonary nodules, with a considerable subset exhibiting no structural abnormalities despite persistent symptoms. The correlation between imaging findings, symptom duration, and smoking burden highlights HRCT's role in delineating clinically significant pathology, particularly in cases where physical examination and conventional radiography are inconclusive.

The high radiological-clinical concordance, especially in emphysema and bronchiectasis, confirms the reliability of HRCT in routine evaluation. Additionally, early structural identification facilitates timely management and may prevent disease progression. The study advocates for broader use of HRCT in high-risk symptomatic smokers, particularly those with substantial tobacco exposure and unexplained symptoms. Future prospective studies integrating pulmonary function tests and biomarker profiling may further refine HRCT’s prognostic value in early-stage pulmonary disease.

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