Validation of AI-Based Detection of Idiopathic Pulmonary Fibrosis in Serial Chest Radiographs: A Retrospective Longitudinal Study

Background:

IPF is an interstitial lung disease with a median survival of 3-5 years following diagnosis. Because interstitial opacity on CXR is subtle in early disease, opportunistic AI-based detection during CXR obtained for unrelated indications (emergency, gastroenterology, cardiology, etc.) could substantially shorten the time to diagnosis. Prior AI-CXR research has largely validated single-timepoint detection performance for findings such as pneumothorax, nodules, and pleural effusion; few studies have quantified how much earlier an AI system can detect interstitial opacity compared with radiologist reporting across a patient's full longitudinal CXR history.

Objectives:

• Quantify the lead-time advantage of AI (VUNO Med-Chest X-ray) versus radiologist reporting for first detection of interstitial opacity in the retrospective CXR series of IPF patients.
• Compare the proportion of early detections (greater than 180 days before diagnosis) between AI and radiologists.
• Explore patient-level effect modifiers of the AI-radiologist lead-time difference (follow-up duration, number of CXRs, prior emphysema/pneumonia history, prior CT availability, CPFE/COPD mention, pulmonology/allergy visit history).
• Examine whether longitudinal AI IO-score trajectory patterns (progressive, oscillating, persistently high) are associated with mortality using Cox proportional-hazards modeling.

Design and methods:

Retrospective, single-center, observational cohort study conducted at Chung-Ang University Hospital (Seoul, Republic of Korea), reported in accordance with STROBE reporting guidelines. The cohort was identified via an April 2025 registry screening of patients carrying an IPF diagnosis at Chung-Ang University Hospital. All available frontal (PA or AP) chest radiographs obtained before each patient's IPF diagnosis date, within a 15-year retrospective imaging window anchored to the April 2025 screening date (January 2010-April 2025), are analyzed with VUNO Med-Chest X-ray (interstitial opacity, consolidation, nodule/mass) and compared against the corresponding radiology reports. Vital status (mortality) was ascertained as of the April 2025 screening date, with no follow-up beyond that cutoff.

Index test: VUNO Med-Chest X-ray interstitial opacity (IO) score, using a pre-specified cutoff (0.35). The AI-detected date is defined as the date of the earliest pre-diagnosis CXR meeting this cutoff.

Comparator: The radiologist-detected date is defined as the earliest chest-radiograph report date containing terminology consistent with reticular pattern / interstitial opacity(reticular opacity) / IO. A sensitivity analysis separately accounts for reports where a chest CT was obtained within +/- 3 months, given the potential influence of CT findings on radiologist reporting. Of 175 enrolled patients with a confirmed IPF diagnosis and an available pre-diagnosis CXR series, 166 comprise the primary paired analysis cohort (AI and radiologist detection dates both available before diagnosis).

Inclusion criteria

• IPF diagnosis on record at Chung-Ang University Hospital as of the April 30, 2025 registry screening, based on imaging findings, pathology results, and clinical information as determined by a pulmonology specialist
• Age greater than or equal to 19 years at IPF diagnosis
• Confirmed diagnosis of IPF (by clinician or multidisciplinary discussion, including CT and/or biopsy)
• Two or more frontal (PA or AP) chest radiographs obtained before the diagnosis date
• DICOM images available and analyzable by VUNO Med-Chest X-ray
• Date of initial IPF diagnosis available

Exclusion criteria

• Only non-frontal chest radiograph views available (e.g., lateral view only)
• One or fewer analyzable chest radiographs
• Missing initial diagnosis date
• No radiology report data available for comparison