Association of antineutrophil cytoplasmic antibody (ANCA) specificity with demographic and clinical characteristics of patients with ANCA-associated vasculitides

INTRODUCTION Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is characterized by the presence of proteinase-3 (PR3) or myeloperoxidase (MPO) ANCA. In over 90% of cases, PR3-ANCA is associated with granulomatosis with polyangiitis (GPA). However, it is also rarely found in microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA). On the other hand, MPO-ANCA being characteristic of MPA (>90% of cases), is also found in about 40% of EGPA and 5% of GPA patients. On the ground of this overlap, clinical importance of ANCA specificity identification has been questioned. OBJECTIVE In this study, we analyzed the clinical and demographic characteristics of AAV subgroups identified by ANCA serotype. PATIENTS AND METHODS We conducted a multicenter study of AAV patients (417 GPA, 106 MPA, 102 EGPA; diagnosed between 1990 and 2016), included in the POLVAS registry. The data were systematically collected according to a standardized protocol. RESULTS In the ANCA-positive group (anti-MPO, anti-PR3) a male-to-female ratio was 1:1, whereas in the ANCA-negative group it was 1:2, regardless of AAV diagnosis. Anti-MPO antibodies were present in significantly older patients. Patients with MPO+GPA and MPO+EGPA were older than those with corresponding ANCA-negative GPA and EGPA as well as PR3+AAV. Moreover, ANCA-negative AAV was characterized by a low risk of end-stage kidney disease and death. CONCLUSIONS The presence and specificity of ANCA in AAV patients are related to sex and age, determine their organ involvement and influence mortality as previously shown. Patients with MPO-ANCA-positive AAV constitute a clinically homogeneous group, whereas PR3-ANCA-positive patients are much more clinically heterogeneous. ANCA-negative AAV patients are characterized by better prognosis. Thus, ANCA identification is an indispensable element and should not be omitted in establishing AAV diagnosis.