ANTINEUTROPHIL CYTOPLASMIC ANTIBODIES (ANCA): THE RELATIONSHIP BETWEEN SEX, AGE AND ANTIGENIC SPECIFICITIES

Background: ANCA are specific and sensitive markers for different vasculitides, i.e.Wegener granulomatosis (WG), Churg Strauss syndrome, microscopic polyangiitis (MPA), for which the term ANCA-associated systemic vasculitis (AASV) is generally used. In patients with systemic vasculitis a significant prevalence of one major antigenic specificities of ANCA, namely proteinase 3 (PR3) or myeloperoxidase (MPO), is now well established. However, the relationships between sex, age and antigenic specificities of ANCA in seropositive patients have not been adequately investigated. Some authors did not find significant difference of gender in ANCA-positive patients, while a study in the Chinese population (1) reported that female patients were younger compared to males.Objectives: to assess possible differences of age and sex in patients with serum anti-Pr3 or anti-MPO antibodies.Methods: We retrospectively evaluated 10.671 serum samples, from a total of 6015 patients, consecutively examined at the laboratory of our hospital from 2003 to 2007 using antigen-specific direct ELISA (PR3- and MPO-ANCA, Hycor company, Great Britain). A cut-off >20 units for used for both autoantibodies.Results: a total of 57 seropositive patients (28M, 29F; mean age 60.7±21yrs) were identified. Among these, 39 patients showed a classical AASV (68%), while 18 affected by other autoimmune diseases (32%). Considering specific autoantibody seropositivity, we found 29 patients with serum anti-PR3 (M/F 17/12, mean age 54±22yrs) and 28 patients with anti-MPO (M/F 11/17,average age total 67±10yrs).There is no difference in gender and the average age of females and males is similar in ANCA-positive patients. There was no correlation between mean age of females and antigenic specificity (65±20yrs vs. 63±13yrs years; respectively), while anti-PR3-positive men were significantly younger compared to anti-MPO-positives (47±20yrs vs. 73±5.yrs) p=0. 001).Conclusion: In the literature, patients with WG are younger than those with MPA, but if we consider the ANCA specificity only males anti-PR3, but not females, are younger than those anti-MPO-positive. These findings, including the results of the present study, remain very difficult to explain. Molecular biology studies on larger patients' populations could better verify their correlations with clinico-epidemiological and demographic features of AASV patients.