Association of antineutrophil cytoplasmic antibody (ANCA) specificity with the 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 are associated with GPA. However, they are also rarely found in MPA and EGPA. On the other hand, MPO-ANCA being characteristic for MPA (>90% of cases), are 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. Patients and methods We conducted a multicenter study AAV patients (417–GPA, 106–MPA, 102-EGPA; diagnosed between 1990 and 2016), included in the POLVAS registry. Data were systematically collected according to a standardized protocol. Results In the ANCA positive group (anti-MPO, anti-PR3) male to female ratio was 1:1, whereas in ANCA negative subgroup - 1:2, regardless of the AAV diagnosis. Anti-MPO antibodies were present in a 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 were characterized by a low risk of ESKD and death. Conclusions The presence and specificity of ANCA in AAV patients is related to sex and age, determines their organ involvement and influences 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.