RELATIONSHIP BETWEEN DISEASE-ACTIVITY AND ANTINEUTROPHIL CYTOPLASMIC ANTIBODY CONCENTRATION IN LONG-TERM MANAGEMENT OF SYSTEMIC VASCULITIS

Autoantibodies directed against neutrophil cytoplasmic antigens (ANCA) are valuable in the diagnosis of primary systemic vasculitis, and imm unofluorescence studies suggest that changes in ANCA concentration ref lect changes in disease activity, We used enzyme-linked immunosorbent assays to examine retrospectively the relationship between ANCA concen tration and disease activity in 56 patients with systemic vasculitis, We included patients with Wegener's granulomatosis, microscopic polyan giitis, idiopathic rapidly progressive glomerulonephritis, and Churg-S trauss syndrome, and examined separately the initial treatment period (mean length of follow-up, 26 months) and long-term management (mean l ength of follow-up, 59 months), Levels of ANCA decreased during induct ion therapy with prednisolone and cyclophosphamide, with or without pl asma exchange, During follow-up, 27 relapses were documented in 20 pat ients (10 with Wegener's granulomatosis, nine with microscopic polyang iitis, and one with Churg-Strauss syndrome), occurring between 4 and 1 83 months (mean, 62 months) after initial presentation, Patients in wh om ANCA were detectable 1 year or more after treatment were at particu lar risk of clinical relapse, Proteinase 3-directed ANCA appeared to b e associated with a higher rate of relapse (44% of patients relapsed) than myeloperoxidase-directed ANCA (13% of patients relapsed). Twenty- four of the 27 relapses occurred in the presence of detectable ANCA; i n 21 of these, ANCA concentration was high or rising, The temporal rel ationship between changes in ANCA concentration and clinical relapse v aried considerably between patients; in seven patients, ANCA remained at high levels for many months (range, 14 to 67 months) before eventua l relapse, One patient showed high concentrations of ANCA over a perio d of 11 years without relapse, In five patients, increases in the ANOA level were not temporally associated with relapse (although four of t hese patients relapsed on other occasions.) We conclude that monitorin g ANCA by enzyme-linked immunosorbent assays is of value in the long-t erm management of patients with Wegener's granulomatosis, microscopic polyangiitis, idiopathic rapidly progressive glomerulonephritis, and C hurg-Strauss syndrome. Increases in ANCA and persistently high levels point to the risk of relapse and indicate the need for frequent clinic al review and continuing maintenance immunosuppression. However, our r esults suggest that ANCA assays should always be used in conjunction w ith other indices of disease activity and should not be the sole basis for changing therapy. (C) 1995 by the National Kidney Foundation, Inc .