Prevalence and Characteristics of Interstitial Lung Abnormalities by Radiologist Report and Quantitative Imaging Analysis in a Lung Cancer Screening Cohort

Introduction / Rationale Interstitial lung abnormalities (ILAs) are highly prevalent and are associated with increased mortality and progression to clinically-evident interstitial lung disease (ILD). Due to shared risk factors (i.e., older age, smoking), individuals enrolled in lung cancer screening (LCS) may be at increased risk for ILAs, however methods to systematically identify these abnormalities through visually-based radiologist reporting or quantitative imaging analysis (QIA) methods have been incompletely explored. Methods Data from Veterans referred to and enrolled in the VA Boston LCS program (4/2019-4/2024) were systematically extracted from the electronic health record (EHR) and included demographics, smoking history, respiratory symptoms (yes/no), and any history of chronic respiratory disease (CRD; yes/no) based on keyword search of the patient's “Active Problems”. Data from clinical pulmonary function tests (PFTs) was also systematically extracted. Among LCS enrollees who completed a low-dose chest computed tomography (LDCT), radiologist-reported ILA (yes/no) was assessed using systematic search for selected keywords within the clinical report. QIA was performed on a subset of LDCTs using the Chest Imaging Platform extension for 3D-Slicer. Three QIA-based definitions for ILA were defined as follows: (a) total volume of high-attenuation areas (HAAs)≥5%, (b) lower lung field HAAs≥5%, and (c) cranial-caudal difference in HAAs≥2%. Differences in the prevalence of clinically-diagnosed CRD, respiratory symptoms, and mean total lung capacity (TLC) by PFTs and QIA by radiologist-reported and QIA-assessed ILA status were assessed using Chi-squared tests or Student's t-tests; a p-value <0.05 was considered significant. Results Among 4,849 unique referrals, 3,445 patients enrolled in LCS and 2,767 had LDCTs completed (mean±SD age 65.8±7.1, 94% male, 60% current smokers, 47.8±21.3 pack-years) and were retained for analysis. 924 patients (33%) had a clinical diagnosis of CRD and 851 patients (31%) reported respiratory symptoms; 1,324 patients (48%) had clinical PFTs performed of which lung volume testing (TLC data) was available in 858 (31%). Overall prevalence of radiologist-reported ILA was 5% (Table 1); among the subset with QIA performed (n=982), the prevalence of ILA varied between 8%-32%. There were no significant differences in clinical CRD diagnosis or respiratory symptoms by the presence/absence of radiologist-reported or QIA-assessed ILA, however, significant differences in TLC by both PFT and QIA methods were observed. Conclusion Both radiologist-reported and QIA-assessed ILA are associated with detectable differences in TLC which may antedate symptoms and clinical diagnoses. Future studies including longitudinal assessments for associations with clinical outcomes are warranted.