Comparison of Interstitial Lung Disease Between Antineutrophil Cytoplasmic Antibodies Positive and Negative Patients: A Retrospective Cohort Study

Objective Positive antineutrophil cytoplasmic antibodies (ANCAs) may occur in the setting of interstitial lung disease (ILD), with or without ANCA‐associated vasculitis (AAV). We aim to compare the characteristics and clinical course of patients with ILD and positive ANCA (ANCA‐ILD) to those with negative ANCA. Methods We performed a single‐center retrospective cohort study from 2018 to 2021. All patients with ILD and ANCA testing were included. Patient characteristics (symptoms, dyspnea scale, and systemic AAV), test results (pulmonary high‐resolution computed tomography and pulmonary function tests), and adverse events were collected from electronic medical records. Descriptive statistics and the Fisher exact test were used to compare the outcomes of patients with ANCA‐ILD to those with ILD and negative ANCA. Results A total of 265 patients with ILD were included. The mean follow‐up duration was 69.3 months, 26 patients (9.8%) were ANCA positive, and 69.2% of those with ANCA‐ILD had another autoantibody. AAV occurred in 17 patients (65.4%) with ANCA‐ILD. In 29.4% of patients, AAV developed following ILD diagnosis. Usual interstitial pneumonia was the most common radiologic pattern in patients with ANCA‐ILD. There was no association between ANCA status and the evolution of dyspnea, diffusing capacity of the lungs for carbon monoxide, and lung imaging. Forced vital capacity improved over time in 42% of patients with ANCA‐ILD and in 17% of patients with negative ANCA (P = 0.006). Hospitalization occurred in 46.2% of patients with ANCA‐ILD and in 21.8% of patients with negative ANCA (P = 0.006). Both groups had similar mortality rates. Conclusion Routine ANCA testing should be considered in patients with ILD. Patients with ANCA‐ILD are at risk for AAV. More research is required to better understand and manage patients with ANCA‐ILD.