European Journal of Cardiovascular Medicine

Lung cancer remains one of the leading causes of cancer-related mortality worldwide, largely due to delayed diagnosis and limited treatment options in advanced stages (1). Cigarette smoking is the most significant risk factor, accounting for nearly 85% of lung cancer cases globally (2). Detecting pulmonary nodules at an early stage in high-risk individuals, such as chronic smokers, can significantly improve survival outcomes through timely intervention (3).

Conventional chest radiography has shown limited sensitivity in identifying small, early-stage pulmonary nodules, prompting the need for more sensitive imaging modalities (4). Computed tomography (CT) has emerged as a valuable tool in the early detection of lung abnormalities; however, concerns regarding cumulative radiation exposure have limited its use in screening programs (5). To address this issue, low-dose computed tomography (LDCT) has been developed as a screening alternative, offering significantly reduced radiation doses while maintaining diagnostic accuracy (6).

Multiple large-scale trials, including the National Lung Screening Trial (NLST), have demonstrated the effectiveness of LDCT in reducing lung cancer mortality in high-risk populations (7). Despite these findings, variability in diagnostic accuracy based on imaging parameters, reader experience, and patient characteristics continues to be a challenge (8). Furthermore, false positives and overdiagnosis remain potential limitations of LDCT screening (9).

This study aims to evaluate the diagnostic accuracy of LDCT in detecting pulmonary nodules in a cohort of chronic smokers by comparing its performance with standard-dose CT (SDCT). The goal is to determine whether LDCT can reliably be used as a first-line screening tool in high-risk populations while minimizing radiation exposure.

A total of 150 participants were recruited based on the following inclusion criteria: individuals aged 45 to 75 years with a history of cigarette smoking ≥20 pack-years, no prior diagnosis of lung malignancy, and no recent respiratory infection or thoracic surgery. Patients with contraindications to CT imaging, known lung cancer, or those unwilling to participate were excluded.

Imaging Procedure
All enrolled participants underwent low-dose computed tomography (LDCT) of the chest using a 64-slice multidetector CT scanner. The LDCT protocol employed the following parameters: tube voltage of 120 kVp, tube current of 30–50 mA, slice thickness of 1.25 mm, and pitch of 1.5. Within 72 hours, each participant underwent a standard-dose CT (SDCT) scan using identical anatomical coverage and reconstruction algorithms to serve as the reference standard.

Image Analysis
Two experienced thoracic radiologists, blinded to clinical data and each other's interpretations, independently reviewed the LDCT and SDCT images. Pulmonary nodules were assessed in terms of number, size (largest diameter), location (lobe-wise), and morphological characteristics. Discrepancies between readers were resolved by consensus.

Data Collection and Statistical Analysis
Data were recorded and tabulated for analysis. The diagnostic accuracy of LDCT was evaluated by calculating sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) using SDCT as the gold standard. Continuous variables were expressed as mean ± standard deviation (SD), and categorical data as frequencies and percentages. Paired t-tests were used to compare mean nodule sizes between modalities, while the chi-square test was applied for categorical comparisons. A p-value <0.05 was considered statistically significant. Statistical analysis was performed using SPSS version 26.0.

Out of the 150 participants screened, 102 individuals (68%) were found to have at least one pulmonary nodule on low-dose computed tomography (LDCT), while 110 participants (73.3%) had nodules detected on standard-dose computed tomography (SDCT). The mean age of participants was 61.4 ± 7.2 years, with a male predominance (78%).

Nodule Detection and Characteristics
LDCT identified a total of 156 nodules across 102 patients, while SDCT revealed 168 nodules in 110 patients. The average size of nodules on LDCT was 5.8 ± 1.6 mm, which was not significantly different from those observed on SDCT (6.0 ± 1.5 mm; p = 0.27). The majority of nodules (62%) were located in the upper lobes in both modalities. Table 1 summarizes the comparison of nodule characteristics detected by LDCT and SDCT.

Table 1. Comparison of Pulmonary Nodule Characteristics Detected by LDCT and SDCT

Diagnostic Accuracy of LDCT
When compared to SDCT as the reference standard, LDCT showed high diagnostic performance. The sensitivity of LDCT for detecting nodules was 92.4%, specificity was 88.3%, positive predictive value (PPV) was 90.1%, and negative predictive value (NPV) was 90.8% (Table 2).

Table 2. Diagnostic Accuracy of LDCT Compared to SDCT

No statistically significant difference was found in the localization of nodules between the two imaging modalities (p = 0.34). Interobserver agreement for LDCT interpretations was high, with a kappa coefficient of 0.86, indicating substantial concordance between the radiologists. These findings suggest that LDCT performs comparably to SDCT in detecting clinically relevant pulmonary nodules (Tables 1 and 2).

This study aimed to evaluate the diagnostic accuracy of low-dose computed tomography (LDCT) in detecting pulmonary nodules among chronic smokers by comparing it with the standard-dose CT (SDCT) as the reference. Our findings demonstrate that LDCT has high sensitivity (92.4%) and specificity (88.3%) in identifying pulmonary nodules, suggesting that it can serve as an effective screening modality in high-risk populations.

The high prevalence of pulmonary nodules detected in our study aligns with prior research that indicates chronic smokers have a significantly elevated risk for developing such lesions (1,2). The sensitivity of LDCT in our study is consistent with results from the National Lung Screening Trial (NLST), which demonstrated a 20% reduction in lung cancer mortality with LDCT screening in high-risk individuals compared to chest radiography (3). Similarly, the NELSON trial reinforced the role of LDCT in early detection and mortality reduction (4).

In our analysis, the mean size of nodules identified by LDCT (5.8 ± 1.6 mm) was not significantly different from those detected by SDCT (6.0 ± 1.5 mm), indicating that LDCT maintains adequate spatial resolution for clinically relevant nodules. Prior studies have also reported that LDCT can reliably detect nodules ≥4 mm in diameter without substantial image degradation (5,6).

The high agreement between readers (κ = 0.86) highlights the reproducibility and reliability of LDCT interpretations, supporting its feasibility in routine clinical practice. Similar interobserver consistency was noted in studies by Revel et al. and Horeweg et al., underscoring the diagnostic confidence provided by LDCT (7,8).

Despite its advantages, LDCT screening is not without limitations. The potential for false positives and overdiagnosis remains a concern, which can lead to unnecessary follow-ups and invasive procedures (9,10). In our cohort, 8% of nodules detected by LDCT were not visualized on SDCT, possibly representing artifacts or non-specific findings, echoing findings from earlier studies (11).

Radiation exposure is a critical consideration in population-based screening programs. LDCT offers a significant reduction in radiation dose—up to 70–90% lower than SDCT—without compromising diagnostic efficacy (12). This feature enhances its utility for annual screening in high-risk groups as recommended by several clinical guidelines (13).

Moreover, our results align with data from the Fleischner Society, which advocates for a size-based risk stratification approach in managing incidentally detected nodules on LDCT (14). The consistency in upper lobe predominance seen in both modalities also reflects the typical distribution pattern of smoking-related pulmonary pathology (15).

In summary, our findings corroborate existing evidence that LDCT is a highly sensitive, specific, and safe imaging modality for early detection of pulmonary nodules in smokers. Its integration into structured screening programs may significantly enhance early lung cancer detection and improve clinical outcomes.

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