Quantitative computed tomography in interstitial lung disease related to ANCA-associated vasculitis: First insights from a mono-centric retrospective cohort

Interstitial lung disease (ILD) is a signi cant manifes- tation of anti‐neutrophil cytoplasmic antibody‐ associated vasculitis (AAV) that can precede or follow its onset and consistently worsens prognosis.1,2 Accurate identi cation and quanti cation of these pulmonary lesions are vital for targeted and early management.3 While spirometry has prognostic value, it is not uni- versally performed.4 Currently, detecting a usual inter- stitial pneumonia pattern on qualitative chest computed tomography (CT) is the only radiological nding with proven prognostic signi cance.3 Semiquantitative eva- luation, though ideal, is di cult to integrate into routine practice as it requires specialized radiologists and suf- fers from signi cant inter‐ and intra‐observer variability, limiting its reproducibility.5 Quantitative CT (QCT) overcomes these issues by being largely operator‐ independent and highly reproducible. Parametric QCT has demonstrated feasibility and validity, meeting Out- come Measures in Rheumatology Clinical Trials criteria for rheumatology tools.6 This densitometric method analyzes voxel attenuation values within the lung volume,7 producing parameters that describe the his- togram of lung densities. Strong evidence correlates these parameters—especially kurtosis, skewness, and mean lung attenuation (MLA)—with radiological ILD extent and pulmonary function in diseases like idio- pathic pulmonary brosis and other rheumatic ILDs.8–10 However, no data exists on QCT's utility in AAV. This study therefore aims to: investigate the role of chest QCT in distinguishing AAV‐ILD from non‐ILD AAV; deter- mine optimal cuto values for the most discriminative QCT parameters; and explore whether these parameters predict overall mortality in AAV patients.