AB0562 Classification of anca associated vasculitis based on PR3 and MPO serology &amp; their outcome: a single centre prospective study
Authors: GG Ekbote, R Gupta, N Mendiratta, N Negalur, M Bindroo, V Singal
Journal: Annals of the Rheumatic Diseases (2017)

<h3>Background</h3> It is often difficult to classify small vessel vasculitis, especially AAV, as Granulomatosis polyangitis [GPA], Microscopic polyangitis [MPA], Eosinophilic granulomatosis polyangitis [EGPA] &amp; Idiopathic cresentic glomerulonephritis. But with the discovery of ANCA, rheumatologists divide this as ANCA positive or negative vasculitis. <h3>Objectives</h3> To classify AAV as anti-proteinase 3 (PR3) antibody+ or anti-myeloperoxidase (MPO) antibody + &amp; compare their clinical presentation &amp; outcome. <h3>Methods</h3> 49 patients were included in our study from August 2011 till January 2017. Patients were classified according to PR3 and MPO serology [based on ELISA]. <h3>Results</h3> Median follow up was 18 months. PR3 + were 38 and 11 patients were MPO+. GPA was significantly higher in PR3 Group vs MPO group [36 (94.7%) vs 1 (9.1%) p&lt;0.0001*] while MPA was significantly lower in PR3 group as compared to MPO (2 [5.3%] vs 5 [45.45%] p=0.001*). All EGPAs were MP0+ (4 [36.35%]). 48 fulfilled ACR clinical criteria for GPA/MPA or EGPA. 1 patient with arteritic anterior ischemic optic neuropathy without any other major organ involvement had significantly higher titres of MPO antibodies &amp; was sorted as unclassified AAV. None were idiopathic crescentic glomerulonephritis in our cohort. 18 were biopsy proven [15 PR3+vs 3 MPO+]. Lung involvement was significantly higher in PR3 group than MPO group (32 [84.2%] vs 6 [54.5%] p=0.037*).Kidney involvement was also more in PR3 group but was not statistically significant (20 [52.6%] vs 4 [36.4%] p=0.341). Upper respiratory involvement was significantly higher in PR3 group (26 [68.4%] vs 3 [27.3%] p=0.014*). Comparision between manifestations of ophthalmic, cardiac, peripheral vascular system &amp; nervous systems of PR3+ &amp; MPO+ groups was not statistically significant. Complete remission without permanent organ damage was seen in 16 (42%) vs 6 (54.5%) in PR3 and MPO groups respectively (p=0.465). Frequency of relapse/refractory disease, though higher in PR3 group, was not statistically significant (PR3 vs MPO, 10 [26.3%] vs 1 [9.1%] p=0.228). Rates of morbidity &amp; mortality were not significant statistically between PR3 &amp; MPO groups (11 [28.9%] vs 2 [18.2%] p=0.476 &amp; 3 [7.9%] vs 1 [9.1%] p=0.899 respectively). Similar comparisons were made between those who were classified clinically as GPA, MPA &amp; EGPA with respect to remission, relapse, morbidity and mortality. All EGPAs achieved remission. Comparison between groups when divided as GPA &amp; PR3 and MPA &amp; MPO did not show statistical significance. 15 patients (all clinically GPA &amp; PR3+) of the cohort [39.5%] received rituximab for relapse/refractory disease during/after initial induction therapy with cyclophosphamide &amp; steroids. <h3>Conclusions</h3> In this study, we did not find any advantage of clinical classification over serological. Wrongly diagnosing patients when disease is still evolving &amp; inter-clinician bias are eliminated when classifying patients according to serology. Classification as PR3 &amp; MPO is simpler and universal. <h3>References</h3> Hunder, G. G. et al. The American College of Rheumatology 1990 criteria for the classification of vasculitis. Introduction. Arthritis Rheum. 33,1065–1067 (1990). Houben E, Bax WA, van Dam B, et al.Diagnosing ANCA-associated vasculitis in ANCA positive patients: A retrospective analysis on the role of clinical symptoms and the ANCA titre. Carubbi. F, ed. Medicine. 2016;95(40):e5096. <h3>Disclosure of Interest</h3> None declared