The “Masking Effect” of emphysema in bronchiectasis-chronic obstructive pulmonary disease overlap syndrome: Why chest radiography is diagnostically futile

ABSTRACT Background and Objective: The coexistence of chronic obstructive pulmonary disease (COPD) and bronchiectasis, termed bronchiectasis-COPD overlap syndrome (BCOS), represents a high-risk clinical phenotype associated with increased mortality and exacerbations. While high-resolution computed tomography (HRCT) is the gold standard for diagnosis, chest X-ray (CXR) remains the primary screening tool in many settings. This study aims to quantify the “masking effect” of emphysema on bronchial markings by evaluating the correlation between CXR grading and validated HRCT severity scores (Bhalla and Smith) in confirmed BCOS patients. Materials and Methods: This retrospective, single-centre study analysed 78 patients confirmed with BCOS based on spirometry and radiological evidence of emphysema. To ensure internal validity, patients with acute exacerbations or pneumonia within the preceding 6 weeks were strictly excluded. Posterior-anterior chest radiographs were scored for hyperinflation, parenchymal opacities and subjective bronchiectasis severity. The relationship between plain radiographic findings and tomographic scores was analysed using Spearman’s rank correlation coefficient. Results: The study population exhibited a mean Smith Score of 1.41 ± 0.75 and a mean Bhalla Extent Score of 1.66 ± 0.88, indicating mild-to-moderate disease severity on average. While a strong positive correlation was observed between the two HRCT-based scores (r = 0.85, P < 0.001), indicating high internal concordance between scoring systems, the correlation coefficients between CXR and HRCT were near zero (Spearman’s rho ≈ 0), indicating a random relationship between CXR sensitivity and true morphological damage. Conclusion: Our findings demonstrate a fundamental “radiological decoupling” in BCOS. Due to the parenchymal masking effect of emphysema – driven by reduced background lung attenuation – plain radiography is not merely less sensitive but diagnostically unreliable in BCOS. Therefore, HRCT should be mandatory for the clinical phenotyping and management of BCOS, regardless of “mild” or “non-specific” findings on CXRs.