Anti-neutrophil cytoplasmic antibody (ANCA) levels directed against proteinase-3 and myeloperoxidase are helpful in predicting disease relapse in ANCA-associated small-vessel vasculitis.

frequently associated with antibodies against PR3 (70–80%) than to MPO (10–30%), while the opposite is true for MPA and RLV, the question is whether it is the ANCA specificity or the clinical syndrome that is related to the relapse risk. Many groups reported an increased relapse rate for patients with PR3- or C-ANCA-related, as compared with MPO- or P-ANCArelated, small-vessel vasculitis but did not subdivide these groups according to the clinical syndrome [9–13]. In one study in 75 patients with ANCA-related MPAu RLV who achieved remission after induction treatment, no difference in relapse rate was observed according to C- or P-ANCA specificity [7], although survival was worse in patients with C-ANCA [14]. In WG patients this issue has as yet not been addressed. In a retrospective study of 137 patients with WG, diagnosed and treated at our hospital between 1990 and 2000, we found a difference in relapse rate between WG patients with PR3, as compared with the small group with MPOANCA specificity (Figure 1). Also, in 47 patients diagnosed during the same time period with MPAuRLV we observed a lower relapse-free survival in PR3-ANCA (ns9; 63% at 5 years) compared with MPO-ANCApositive patients (ns38; 84% at 5 years), although the difference was not statistically significant.