Prediction of relapses in Wegener's granulomatosis by measurement of antineutrophil cytoplasmic antibody levels - A prospective study

Objective. Prediction of relapses in Wegener's granulomatosis (WG) by measu ring levels of antineutrophil cytoplasmic antibodies (ANCA) directed agains t proteinase 3 (PR3) or myeloperoxidase (MPO) remains a controversial issue . To assess the value of serial quantification of ANCA by indirect immunofl uorescence (IIF) and antigen-specific enzyme-linked immunosorbent assay (EL ISA) for monitoring disease activity in patients with WG, a prospective obs ervational study was conducted in patients with WG attending an outpatient clinic in the Netherlands. Methods. One hundred patients with WG (85 with PR3-ANCA, 15 with MPO-ANCA) were studied prospectively from 1996 to 1998. Serum samples were obtained a nd analyzed every 2 months for ANCA levels. Disease activity was prospectiv ely assessed without knowledge of the ANCA levels. Results. Relapses occurred in 37 of 100 patients (37%). Thirty-four (92%) o f the 37 patients showed a rise in the level of ANCA preceding their relaps e, as detected by ELISA or IIF. The predictive value of an increase in ANCA titers for relapse was 57% (17 of 30) for cytoplasmic/classic ANCA (cANCA; by IIF), 71% (27 of 38) for PR3-ANCA (by ELISA), and 100% (3 of 3) for MPO -ANCA (by ELISA). The predictive value of a rise in ANCA as measured by ELI SA or IIF did not substantially improve following concomitant measurement o f the IgG3 subclass of PR3-ANCA. Forty-three percent of patients who showed a rise in cANCA (by IIF) and 29% with a rise in PR3-ANCA (by ELISA) did no t subsequently experience a relapse. Conclusion. Serial measurement of ANCA levels is valuable for the early pre diction of relapses in patients with WG.