A comparative study of the diagnostic accuracy of ELISA systems for the detection of anti-neutrophil cytoplasm antibodies available in Japan and Europe.

OBJECTIVES: Primary systemic vasculitis associated with anti-neutrophil cytoplasm antibodies (ANCA) differs in its frequency and clinical expression between Japan and Europe. We sought to ascertain whether such differences arise from the performance of enzyme-linked immunosorbent assays (ELISAs) for ANCA. METHODS: Plasma samples from 64 consecutive Japanese patients with a clinical and histological diagnosis of primary systemic vasculitis including microscopic polyangiitis (MPA; n=52), Churg-Strauss syndrome (CSS; n=1), and Wegener's granulomatosis (WG; n=11), or those from disease controls with non-vasculitic glomerulonephritis (n=54) and healthy controls (n=55) were tested for the presence of myeloperoxidase (MPO) by ELISAs available in Japan (Nipro and MBL) and compared with those in Europe (Wieslab). The sensitivity and specificity were calculated for each ELISA, and its diagnostic performance was assessed by receiver operating characteristic curve analysis. RESULTS: The sensitivity and specificity of either MPO-ANCA assays for a diagnosis of MPA were 90.4% and 98.2% (Nipro), 88.2% and 96.3% (MBL), and 86.5% and 99.1% (Wieslab). The overall diagnostic performance, assessed as the area under curve of the MPO-ANCA ELISAs for MPA were 0.946+/-0.022 (Nipro), 0.970+/-0.017 (MBL), and 0.971+/-0.017 (Wieslab), while that of PR3-ANCA ELISAs for WG were 0.986+/-0.025 (Nipro), 0.993+/-0.017 (MBL), and 0.916+/-0.059 (Wieslab). CONCLUSIONS: The MPO-ANCA ELISAs commercially available in Japan exhibited high sensitivity and specificity for the diagnosis of ANCA-associated vasculitides and provided similar diagnostic value to those in Europe. These results facilitate further international comparison of ANCA-associated vasculitides between Japanese and European populations.

ANCA-associated vasculitis in Hispanic Americans: an unrecognized severity.

This study aims to compare the severity and outcomes of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) between Hispanics and Caucasians living in the same geographical area. All patients diagnosed with AAV at two academic institutions in Chicago from January 2006 to December 2012 were retrospectively and prospectively identified. Disease activity was measured with the Birmingham Vasculitis Activity Score (BVAS), and disease damage was measured with the Vasculitis Damage Index (VDI). Student's t test and chi-square tests were employed; p ≤ 0.05 was considered significant. Seventy patients with AAV were identified; 15 patients were excluded. Fifty-five patients were included in the study: 23 Hispanics and 32 Caucasians, 35 patients with granulomatosis with polyangiitis (Wegener's), 12 with microscopic polyangiitis, 7 with eosinophilic granulomatosis with polyangiitis, and 1 with renal-limited vasculitis. Compared to Caucasians, Hispanics had a higher BVAS at presentation (16.3 ± 7.6 versus 10.7 ± 7.5, p = 0.006), a higher VDI at presentation (2.90 ± 1.50 versus 2.06 ± 1.30, p = 0.030), and a cumulative VDI (3.90 ± 1.70 versus 2.50 ± 1.90, p = 0.010). Renal involvement was more common among Hispanics (85 % of Hispanics versus 48 % of Caucasians, p = 0.01). Seventy percent of Hispanics had acute renal failure (mean creatinine = 3.37 ± 4.4 mg/dl) of whom seven (50 %) required dialysis, versus 25 % of Caucasians (mean creatinine = 1.78 ± 1.57 mg/dl, p = 0.03) and only two requiring dialysis. Compared to Caucasians, Hispanics with AAV present with more severe disease and higher damage indices. Larger studies are required to confirm these findings and delineate the respective roles of environment and genetics in the pathogenesis of the disease.