Complement levels according to ANCA serotype, disease phenotype, new diagnosis or relapsing disease or treatment-naïve versus treated patients
There was no difference in MAC, C5a, C3a, factor B, and properdin levels between PR3-ANCA positive and MPO-ANCA positive patients, between patients with GPA and MPA, between patients with newly diagnosed AAV or relapsing disease, and between treatment-naïve patients and those already receiving immunosuppression (Supplementary tables S3-6).
We also evaluated activation of the complement system in patients with ‘non-severe’, ‘severe PR3-ANCA positive’ and ‘severe MPO-ANCA positive’ AAV, representing the predominantly granulomatous, mixed granulomatous-vasculitic and predominantly vasculitic patterns of AAV [16]. Non-severe AAV (usually PR3-ANCA positive or sometimes ANCA-negative) was defined as granulomatosis (ENT-disease, lung nodules/masses, retroorbital tumor and/or pachymeningitis) without life/organ-threatening disease, whereas ‘severe’ vasculitis-related manifestations included glomerulonephritis, alveolar hemorrhage, mononeuritis multiplex, and scleritis. Median levels of all studied complement components were similar in these groups of patients (Supplementary table S7).
Furthermore, patients were distributed into two groups depending on the severity of disease that was defined as the presence of at least one major BVAS item and a total BVAS>6. Median BVAS scores in patients with severe and non-severe AAV were 15 (13;16) and 8 (6;9), respectively. Complement component levels did not differ between patients with severe and non-severe vasculitis (Supplementary table S8).