Note: *p<0.05, ***p<0.001. Changes in complement component levels were studied in 28 patients who have undergone repeated testing following remission induction therapy. Using data from the control group, the upper reference levels of the complement components were defined as following: MAC – 11271.1 mAU/ml, С5а – 33.1 ng/ml (three outliers were excluded), С3а – 8955.3 ng/ml, factor B – 2864.1 µg/ml. The lower reference level of properdin was defined as a cut-off of 357.8 µg/ml. Abbreviations: AAV (ANCA-associated vasculitis), MAC (membrane attack complex).