Lungenfunktion bei ANCA-assoziierten Vaskulitiden: eine retrospektive Untersuchung zur Spirometrie, Bodyplethysmographie und CO-Diffusionskapazität

Abstract

Background/Objectives: Pulmonary involvement is common for (ANCA)-associated vasculitis (AAV) but there are only few studies concerning impairment of pulmonary function in those patients. In this work pulmonary function test (PFT) data of patients with granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA) were evaluated to quantify possible changes in lung function. Results were also analyzed for a correlation with findings in diagnostic imaging, clinical course, and disease activity.

Methods: Patients with diagnosed GPA (n=81), MPA (n=37), and EGPA (n=29) according to ACR criteria and a valid PFT were identified from the database of our vasculitis center. Cases with acute pulmonary comorbidities unrelated to AAV were excluded. The PFT comprised spirometry including helium dilution technique, body plethysmography, and measurement of diffusing capacity. The collected data among others included forced vital capacity (FVCex), peak expiratory flow (PEF), Tiffeneau-Index (rFEV1), total airway resistance (RAWtot), total lung capacity (TLC), residual volume (RV), and transfer factor for carbon monoxide (TLCO). For the analysis these measures were expressed as percentage of predicted values.

Results: For the GPA cohort, FVCex, RV, PEF and TLCO were significantly reduced. However, there was no significant difference between patients with or without pulmonary manifestation. In patients with MPA, distinct reductions of FVCex, TLC and TLCO were observed compared to the standard population. These changes were significantly stronger in MPA patients with pulmonary involvement. For the EGPA group RAWtot and RV were significantly elevated and TLCO was reduced. Lung fibrosis correlated with a decline between 16-39% of FVCex, TLC, RV and TLCO. Patients with scarring showed decreased measures for TLCO and those with consolidations for TLC. Additionally, both signs were connected to an impairment of FVCex. Regarding the disease process no significant difference occurred between first PFT and follow-up. Additionally, there was no correlation found between disease activity and PFT.

Conclusion: GPA showed no significance for an impairment in PFT but there were hints for a reduced gas transfer and upper airway lesions. MPA revealed a restrictive ventilatory defect and a reduced diffusion capacity that were both attributable to the AAV and more common in patients with pulmonary fibrosis. As expected, many patients with EGPA had an obstructive ventilatory pattern which is probably related to the accompanying asthma. AAV-patients with scarring seemed to suffer more often from impaired diffusion capacity whereas patients who showed signs of consolidation have had a higher risk for a restrictive pattern. Lacking evidence for changes in PFT over time and no correlation found between PFT and disease activity suggest non-reversible damage. Summing up, PFT should be included in future prospective clinical trials in patients with AAV.