Interobserver Variability in Lung-RADS Categorization Between Tertiary and Non-Tertiary Hospitals, and Its...

Background/Objectives: Lung-RADS was introduced to standardize the management of nodules detected during lung cancer screening. However, significant interobserver variability has been reported, and its consistency across different hospital settings remains insufficiently investigated. This study aimed to compare Lung-RADS categorization and diagnostic performance between tertiary and non-tertiary hospitals, and to evaluate interobserver variability and associated differences in recommended management. Methods: This single-tertiary-center, referral-based retrospective study included patients referred to a tertiary hospital after lung cancer screening at 29 non-tertiary hospitals between September 2019 and December 2023. CT images were reinterpreted at a tertiary hospital using Lung-RADS. A blinded review was performed by an independent thoracic radiologist, and interobserver variability was assessed using Cohen's kappa. Discordance rate and major discordance (≥9-month follow-up difference) were determined. Sensitivity, specificity, and diagnostic accuracy were calculated and compared. Results: Sixty patients (median age, 63 years [interquartile range, 58-68]; 59 men and one woman) with 43 confirmed final diagnoses (18 of lung cancer and 25 of benign lesions) were included. Interobserver variability was fair between tertiary and non-tertiary hospitals (κ = 0.30), and between non-tertiary hospitals and thoracic radiologist (κ = 0.28), but almost perfect between tertiary hospital and thoracic radiologist (κ = 0.82). Lung-RADS discordance occurred in 50.0% of the cases (30/60), with 70.0% (21/30) classified as major discordance. Among the 43 patients with confirmed final diagnoses, specificity was significantly higher in tertiary hospital reports (68.0%, 95% CI 46.5-85.1) compared to non-tertiary hospital reports (20.0%, 95% CI 6.8-40.7; p = 0.001), while sensitivity was comparable (100.0%, 95% CI 81.5-100 vs. 88.9%, 95% CI 65.3-98.6; p = 0.480). Conclusions: Frequent discordances in Lung-RADS categorization were observed between tertiary and non-tertiary hospitals. Higher specificity was observed for tertiary hospital interpretations within this referral cohort. These discrepancies may affect patient management, highlighting the need for strategies to improve consistency.