264. Pulmonary function in patients with ANCA-associated Vasculitis

Background: Although, pulmonary manifestations occur frequently in antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV), empirical evidence of their impact on pulmonary function testing (PFT) is scarce. This project analyzed lung function data from a large cohort of patients with granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA) to quantify a possible change in lung function according to each subtype. Methods: Patients with AAV and least one valid PFT during their medical treatment encompassing the time period from 2008-2018 were identified retrospectively from the database of our vasculitis center in a tertiary university hospital. Patients with significant acute pulmonary comorbidities unrelated to AAV were excluded. The PFT comprised spirometry, plethysmography, and measurement of diffusing capacity including helium dilution technique. Data on forced vital capacity (FVCex), Tiffeneau-Index (rFEV1), total airway resistance (RAWtot), total lung capacity (TLC), residual volume (RV), and transfer factor (TLCO) were recorded. For the analysis these measures were expressed as a percentage of predicted values. First, the mean was compared to the defined standard value of the population (100%). Additionally, there was a comparison between patients with/without pulmonary manifestation in case history. Data were analyzed according to their distribution with t-test or Mann-Whitney-U-test for a significance level of α = 5%. Results: Table 1. In total, 147 AAV-patients (GPA: n=81; MPA: n=37; EGPA: n=29) were included, of which 98 had a history of pulmonary involvement (GPA: n=50; MPA: n=20; EGPA: n=28). The mean age at the time of PFT was 58.5 years. Patients had a median disease duration of 8.5 months. In patients with GPA, FVCex, RV and TLCO were significantly reduced compared to expected normal values of 100% predicted. However, there was no significant difference between patients with or without pulmonary manifestations. In patients with MPA, even stronger reductions of FVCex and TLCO were observed compared to the population. These were accompanied by a decrease of TLC. The restrictive pattern and impairment of CO diffusion capacity was significantly stronger in MPA-patients with pulmonary involvement compared to patients without. In EGPA-patients RAWtot and RV were significantly elevated and TLCO was reduced. Conclusions: Patients with MPA and interstitial lung disease show a significant restrictive ventilatory defect which is accompanied by a reduction of CO diffusion capacity compared to MPA-patients without pulmonary manifestation. As expected, many patients with eGPA have an obstructive ventilatory pattern which is related to the accompanying asthma. The interpretation of our data is limited by the retrospective design and potential indication bias for PFT. Pulmonary function testing should be included in future prospective clinical trials in patients with AAV. Disclosures: The authors declare that there is no conflict of interests as defined by the International Committee of Medical Journal Editors