Demographic data included age at the onset of disease, gender, marital status, initial clinical manifestations, disease activity at the time of the diagnosis by BVAS and follow-up duration (defined as the period from diagnosis to the last visit). At each relapse, the BVAS score and the time between the first presentation and each relapse using the BVAS version 3 (BVAS v3). Laboratory variables at the time of diagnosis, and each relapse was collected. Namely, blood count CBC, Renal Function test, urinary red blood cell/ white blood cell count, 24-h urinary protein, Inflammatory markers (ESR, CRP), P-ANCA and C-ANCA, Rheumatoid factor RF, Complements level (C3, C4). C3, C4 are both analyzed by immunoturbidimetry, ANCA is analyzed by indirect immunofluorescence, anti-PR3/anti-MPO antibodies analyzed by antigen-specific enzyme-linked immunosorbent assay (ELISA) and rheumatoid factor analyzed by the agglutination test. Remission was defined as disappearance of clinical disease activity and stabilization or improvement of the kidney function or BVAS=0.17 Resolution of hematuria was also considered criteria for remission.15

Relapse was defined as an increase in serum creatinine level accompanied with GFR decline, new RBC cast above 5 cells, new proteinuria above 500 mg over 24 hours not explained by any other secondary causes, worsening or new extrarenal manifestations attributable to active vasculitis after a time of remission, with or without increase in ANCA titers.12 Complications encountered (namely, infection required hospitalization, thrombotic events, malignancy and infertility) and disease outcomes were also recorded.

Medications during the remission induction and maintenance phase were identified. All patients received induction therapy with various combinations of corticosteroids and immunosuppressants based on the European Vasculitis Study Group (EUVAS) and the EULAR/ERA-EDTA consensus recommendations.18 Namely, intravenous Cyclophosphamide, Rituximab, Azathioprine, Methotrexate, Mycophenolate Mofetil, plasma exchange, and Intravenous Immunoglobulin (IVIG).