C-Reactive Protein Levels Are Associated with Complement C4 Deposits and Interstitial Arteritis in ANCA-Associated Renal Vasculitis.

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a potentially life-threatening systemic small-vessel vasculitis that is characterized by pauci-immune glomerulonephritis in case of kidney involvement, representing a major denominator of AAV mortality. Innate immunity with complement system activation is increasingly recognized in the pathogenesis of AAV and as an attractive therapeutic target. Although C-reactive protein (CRP) was thought to be a passive, nonspecific marker of inflammation, recent studies indicate that CRP plays a key role in the innate immune system by recognizing pathogens and altered self-determinants. Elevated baseline CRP at disease onset of AAV has already been described as a determinant of poor long-term outcomes. However, its clinical implications at disease onset of AAV, with respect to vasculitis manifestations and complement system activation that might also affect long-term outcomes, remain elusive. CRP levels were retrospectively analyzed in 53 kidney-biopsy-confirmed cases of ANCA-associated renal vasculitis; a total of 138 disease controls were also evaluated. Univariate and multivariate regression analysis was performed on clinicopathological parameters associated with CRP levels in ANCA-associated renal vasculitis. Results: Compared to disease controls, CRP elevation was common in ANCA-associated renal vasculitis and associated with de novo disease (p = 0.0169), critical illness (p = 0.0346), and severe deterioration of kidney function (p = 0.0167), independent of extrarenal disease manifestations. As confirmed by multiple regression analysis, CRP levels were correlated with active lesions predominated by interstitial arteritis in renal vasculitis, specifically with MPO-ANCA seropositivity (p = 0.0017). Based on analysis of systemic complement system activation and intrarenal complement deposits, CRP elevation was correlated specifically with complement C4 deposits in interstitial arteries in the subgroup with myeloperoxidase (MPO)-ANCA seropositivity (p = 0.039). Finally, this association was independent of systemic complement system activation, as reflected by the consumption of respective complement components. Here, we expand our current understanding of CRP in ANCA-associated renal vasculitis not only as an inflammatory marker, but potentially also as being involved in the pathogenesis of kidney injury by interaction with the complement system.

Identification and functional characterization of a novel susceptibility locus for small vessel vasculitis with MPO-ANCA.

OBJECTIVE: To identify and characterize genetic loci associated with the risk of developing ANCA-associated vasculitides (AAV). METHODS: Genetic association analyses were performed after Illumina sequencing of 1853 genes and subsequent replication with genotyping of selected single nucleotide polymorphisms in a total cohort of 1110 Scandinavian cases with granulomatosis with polyangiitis or microscopic polyangiitis, and 1589 controls. A novel AAV-associated single nucleotide polymorphism was analysed for allele-specific effects on gene expression using luciferase reporter assay. RESULTS: PR3-ANCA+ AAV was significantly associated with two independent loci in the HLA-DPB1/HLA-DPA1 region [rs1042335, P = 6.3 × 10-61, odds ratio (OR) 0.10; rs9277341, P = 1.5 × 10-44, OR 0.22] and with rs28929474 in the SERPINA1 gene (P = 2.7 × 10-10, OR 2.9). MPO-ANCA+ AAV was significantly associated with the HLA-DQB1/HLA-DQA2 locus (rs9274619, P = 5.4 × 10-25, OR 3.7) and with a rare variant in the BACH2 gene (rs78275221, P = 7.9 × 10-7, OR 3.0), the latter a novel susceptibility locus for MPO-ANCA+ granulomatosis with polyangiitis/microscopic polyangiitis. The rs78275221-A risk allele reduced luciferase gene expression in endothelial cells, specifically, as compared with the non-risk allele. CONCLUSION: We identified a novel susceptibility locus for MPO-ANCA+ AAV and propose that the associated variant is of mechanistic importance, exerting a regulatory function on gene expression in specific cell types.

Ageing enhances cellular immunity to myeloperoxidase and experimental anti-myeloperoxidase glomerulonephritis.

OBJECTIVES: ANCA-associated vasculitis (AAV) is an autoimmune disease characterized by small blood vessel inflammation, commonly affecting the kidneys and respiratory tract. It is unclear why the incidence of this condition increases with age. Previous studies in a passive antibody transfer system in aged mice have implicated innate effectors. To test the hypothesis that autoimmunity to myeloperoxidase (MPO), an autoantigen responsible for AAV, increases with age, anti-MPO autoimmunity was studied in murine models of active autoimmunity and disease induced by cellular immunity. METHODS: Young (8 weeks) and aged (either 15 or 22 months) mice were immunized with whole proteins or peptides from ovalbumin, as a model foreign antigen, or MPO protein or peptides. Mice were subjected to a model of active anti-MPO glomerulonephritis. Cellular and humoral immune responses, and tissue inflammation were assessed. RESULTS: While cellular immunity to ovalbumin was diminished in aged mice, cellular autoimmunity to MPO and its immunodominant CD4+ and CD8+ T cell epitopes was increased after immunization with either MPO peptides or whole MPO protein, assessed by peptide and antigen-specific production of the pro-inflammatory cytokines IFN-γ and IL-17A. MPO-ANCA titres were not increased in aged mice compared with young mice. In experimental anti-MPO glomerulonephritis, cell-mediated injury was increased, likely due to CD4+ and CD8+ T cells, innate immunity and the increased vulnerability of aged kidneys. CONCLUSION: Heightened cellular immunity to MPO develops with ageing in mice and may contribute to the increased incidence and severity of AAV in older people.

Interstitial Lung Disease in ANCA-Associated Vasculitis: Pathogenic Considerations and Impact for Patients' Outcomes.

PURPOSE OF REVIEW: This review provides an update on recent advances in the diagnosis, pathogenesis, clinical presentation, histopathological findings, and treatment approaches for antineutrophil cytoplasmic antibody (ANCA) vasculitis-associated interstitial lung disease (AAV-ILD) with a focus on literature published in the last 3 years. RECENT FINDINGS: Although there is no validated definition of AAV-ILD, which contributes to some of the heterogeneity seen in study results, there has been an increasing number of publications in recent years on this topic. Most patients with AAV-ILD have MPO-ANCA vasculitis, and this association appears to reduce their 5-year-survival to 60-66% (Sun et al. BMC Pulm Med 21(1), 2021, Maillet et al. J Autoimmun 106, 2020). Median age of diagnosis ranges from mid-60 s to mid-70 s (Ando et al. Respir Med 107(4), 2013), Kagiyama et al. BMJ Open Respir Res 2(1):1-9, 2015, Hozumi et al. Lung 194(2):235-42, 2016, Liu et al. Chest 156(4):715-23, 2019, Maillet et al. J Autoimmun 106, 2020, Wurmann et al. Sarcoidosis Vasc Diffuse Lung Dis 37(1):37-42, 2020, Watanabe et al. BMC Pulm Med 19(1), 2019). Computed tomography (CT) chest imaging for patients with AAV-ILD often shows a usual interstitial pneumonia (UIP) or nonspecific interstitial pneumonia (NSIP) pattern (12-58% and 13-61%, respectively) (Sun et al. BMC Pulm Med 21(1), 2021, Maillet et al. J Autoimmun 106, 2020, Wurmann et al. Sarcoidosis Vasc Diffuse Lung Dis 37(1):37-42, 2020, Watanabe et al. BMC Pulm Med 19(1), 2019, Baqir at al. Sarcoidosis Vasc Diffuse Lung Dis Off J WASOG 36(3):195-201, 2019). Additionally, lung biopsies typically do not demonstrate active inflammation, or capillaritis, questioning whether these patients should be treated with either immunotherapy or anti-fibrotic therapy, or both (Hozumi et al. Lung 194(2):235-42, 2016, Liu et al. Chest 156(4):715-23, 2019, Kitching at al. Nat Rev Dis Prim 6(1):71, 2020, Tanaka et al. Respir Med 106(12):1765-70, 2012). Besides immunosuppressive treatments, recent advances in anti-fibrotic therapy may offer patients with progressive AAV-ILD an alternative and/or more effective and individualized treatment option.

The efficacy and safety of mizoribine for maintenance therapy in patients with myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA)-associated vasculitis: the usefulness of serum mizoribine monitoring.

BACKGROUND: The life prognosis of elderly patients with myeloperoxidase-anti-neutrophil cytoplasmic antibodies-associated vasculitis (MPO-AAV) has been improved by reducing the corticosteroid or cyclophosphamide dose to avoid opportunistic infection. However, many elderly MPO-AAV patients experience recurrence and renal death. An effective and safer maintenance treatment method is necessary to improve the renal prognosis of MPO-AAV. METHODS: Patients with MPO-AAV who reached complete or incomplete remission after induction therapy were prospectively and randomly divided into mizoribine (MZR; n = 25) and control (n = 28) groups. The primary endpoint was relapse of MPO-AAV. The patients' serum MZR concentration was measured before (C0) and 3 h after taking the MZR. The maximum drug concentration (Cmax) and the serum MZR concentration curves were determined using population pharmacokinetics parameters. We also assessed the relationship between the MZR concentrations and adverse events. The observation period was 12 months. RESULTS: Fifty-eight MPO-AAV patients from 16 hospitals in Japan were enrolled. Ten patients relapsed (MZR group, n = 6; control group, n = 4; a nonsignificant between-group difference). Changes in the serum MZR concentration could be estimated for 22 of the 25 MZR-treated patients: 2 of the 11 patients who reached a Cmax of 3 µg/mL relapsed, whereas 4 of the 11 patients who did not reach this Cmax relapsed. The treatment of one patient with C0 > 1 µg/mL was discontinued due to adverse events. No serious adverse events occurred. CONCLUSION: There was no significant difference in the recurrence rate of MPO-AAV between treatment with versus without MZR.

Hypertrophic Pachymeningitis Development in Eosinophilic Granulomatosis with Polyangiitis at Relapse of Disease: A Case-Based Review.

Hypertrophic pachymeningitis (HP) presents with thickening of the dura mater in the cerebrum and spine, and its symptoms vary depending on the affected location. The association of HP with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis has been recognized, and most cases are complicated by granulomatosis with polyangiitis. We report the case of a 47-year-old man who presented with HP upon relapse of eosinophilic granulomatosis with polyangiitis (EGPA), with literature review. He presented with disturbance of consciousness, and magnetic resonance imaging (MRI) revealed thickening of the dura mater around the left parietal lobe. Although myeloperoxidase (MPO)-ANCA was positive on EGPA diagnosis, the elevation of MPO-ANCA was not documented at the onset of HP. Brain perfusion scintigraphy showed an increase in blood flow in the left parietal lobe and temporal lobe, and electroencephalogram (EEG) revealed slow waves in the left parietal lobe. He was treated with a high dose of corticosteroid and rituximab, and the slow waves on EEG and brain perfusion were normalized. Although the most frequent symptom of HP is headache, disturbance of consciousness can be the manifestation of HP, and inflammation of HP could affect the cerebral parenchyma, which can be documented as abnormal EEG and perfusion scintigraphy. Literature review revealed that most of the HP in EGPA developed when EGPA relapsed, and was observed in patients with MPO-ANCA positivity. HP develops without evidence of other clinical features of EGPA; therefore, adequate imaging, including contrast-enhanced MRI, is necessary. Rituximab may be effective for treating HP complicated with EGPA.

Anti-neutrophil cytoplasmic antibodies predate symptom onset of ANCA-associated vasculitis. A case-control study.

OBJECTIVES: Anti-neutrophil cytoplasmic autoantibodies [ANCA) are important for diagnosis of ANCA-associated vasculitides (AAV). The timing of antibody development is not well established. To investigate the development of proteinase 3 (PR3)- and myeloperoxidase (MPO)-ANCA, blood samples collected before onset of symptoms of AAV were analysed. METHODS: To identify AAV patients with blood samples predating symptoms, the National Patient Register and Cause of Death register were scrutinized for ICD codes for AAV and linked to the registers of five biobanks. Diagnoses of AAV and time point for symptom onset were confirmed by reviewing 504 case-record. Eighty-five AAV cases (34 males, 51 females) with samples >1 month < 10 years from AAV symptom onset and two controls matched for sex, age, and sampling time for each case were included. Samples were screened using ELISAs for ANCA and further analysed for PR3-or MPO- specificities. RESULTS: In ANCA-screen 35.7% of the pre-symptomatic cases and 3.5% of controls tested positive (p < 0.01). 26.2% of the cases were PR3-ANCA+ and 10.7% MPO-ANCA+. Median (Q1-Q3) predating time for PR3-ANCA+ was 2.7 (0.3-7.7) years and MPO-ANCA+ 2.0 (0.9-3.5) years. PR3-ANCA was demonstrated in samples up to nine years before symptom onset. At symptom onset predating PR3-ANCA+ cases were younger than PR3-ANCA- (P < 0.01), and MPO-ANCA+ were older than MPO-ANCA- (p < 0.05). Predating MPO-ANCA+ cases vs. MPO-ANCA- and vs. PR3-ANCA+ cases had more often at symptoms onset manifestations from lungs, kidneys or peripheral nervous system (p < 0.01 and p < 0.05, respectively). CONCLUSION: The PR3-and MPO-ANCAs are present years before AAV symptom onset and represent distinct diseases.

Evaluation of PR3- and MPO-ANCA line and dot immunoassays in ANCA-associated vasculitis.

OBJECTIVE: This study was performed to evaluate the diagnostic accuracy of novel line and dot immunoassays for detection of MPO and PR3 ANCA. METHODS: Sera from 50 patients with ANCA-associated vasculitis (AAV), including granulomatosis with polyangiitis and microscopic polyangiitis, and from 45 disease controls were tested by IIF and for the presence of PR3-ANCA and MPO-ANCA by four different line or dot immunoassays, as well as by a chemiluminescence immunoassay. RESULTS: The area under the curve of the receiver operating characteristic curve to discriminate AAV from controls was 0.858 (95% CI 0.785-0.931) for the IIF method. For the antigen-specific immunoassays, the area under the curve varied between 0.869 (95% CI 0.797-0.941) and 0.936 (95% 0.886-0.985). CONCLUSIONS: Our comparison of various ANCA detection methods showed a high degree of diagnostic precision for all of the PR3- and MPO-ANCA line and dot immunoassays investigated. The performance was equal to or better than the performance of IIF. These results indicate that novel line and dot immunoassays can serve as a first-line test method in patients with the suspected diagnosis of AAV.

Impaired HVJ-stimulated Interferon producing capacity in MPO-ANCA-associated vasculitis with rapidly progressive glomerulonephritis lead to susceptibility to infection.

ANCA-associated RPGN leads to renal failure through systemic vasculitis and diffuse crescentic glomerulonephritis. MPO-ANCA-RPGN patients are highly susceptible to infections. Our aim in this study was to uncover reasons why these patients were susceptible to infections. We analyzed various aspects of type I interferon system including HVJ-stimulated IFN-α producing capacity and plasmacytoid dendritic cell (pDC) number in whole blood in MPO-ANCA-RPGN patients. Compared with healthy subjects, MPO-ANCA-RPGN patients showed impaired HVJ-stimulated IFN-α producing capacity and lower pDC number with or without glucocorticoid treatment. Immuno-histological staining of MPO-ANCA-RPGN kidney samples revealed a few but apparent pDC in T cell infiltrating regions even in patients with low pDC number in their peripheral blood. Patients' low HVJ-stimulated IFN-α producing capacity and pDC numbers persisted even after patients underwent several years of treatment. Former infection was determined using patients' serum BPI, Lamp-2 and Calprotectin, since they are reflective of a history of infection. These markers were higher in MPO-ANCA-RPGN patients than in healthy subjects. These results indicate that impaired HVJ-stimulated IFN-α production as well as dysfunction of the IFN system might have resulted from a previous bout of infection and can be partially implicated in patients' long-term susceptibility and vulnerability to infection.

Rapidly progressive glomerulonephritis due to systemic lupus erythematosus and ANCA-associated vasculitis overlap.

Systemic lupus erythematosus (SLE) and ANCA-associated vasculitis (AAV) are different autoimmune diseases. While vasculitis can be seen in the SLE clinical course as a secondary phenomenon, and may indicate a severe disease, primary vasculitis such as AAV rarely occurs in association with SLE. We present a 44-year-old woman who presented with rapidly progressive glomerulonephritis which was histologically identified as a combination of crescentic and lupus nephritis in the presence of myeloperoxidase ANCA antibody. The frequency of this association is very rare. The clinical, histological and immunological features are different in SLE/AAV overlap syndrome and need different treatment options, which may include rituximab, to achieve complete recovery. Since SLE/AAV overlap can be serious at presentation, the physician must be aware of this syndrome.

Association between preexisting lung involvements and the risk of diffuse alveolar hemorrhage in patients with microscopic polyangiitis: A multi-center retrospective cohort study.

Objectives: To identify the factors associated with the risk of diffuse alveolar hemorrhage (DAH) in patients with microscopic polyangiitis (MPA), focusing on other preexisting lung involvements such as interstitial lung disease (ILD) and airway disease.Methods: In this retrospective cohort study, we analyzed consecutive patients with myeloperoxidase-antineutrophil cytoplasmic antibody-positive MPA who had undergone chest computed tomography (CT) before starting treatment between 2006 and 2016. Patients who already had DAH at initial CT imaging were excluded. CT images were evaluated for the presence of ILD and airway disease. The association between preexisting lung involvements and the development of DAH was assessed using logistic regression models adjusted for various clinical characteristics.Results: We identified 113 patients (median age 72 years; median follow-up duration 39 months), and 27 (24%) of them developed DAH during the follow-up. Airway disease was identified in 41 (36%) patients and was independently associated with the development of DAH (adjusted odds ratio 6.86, 95% confidence interval 1.85-25.4). However, ILD identified in 45 (40%) patients was not associated with DAH.Conclusion: Our findings suggest that DAH in MPA occurs frequently in patients with airway disease. Attention to preexisting airway disease may help predict the development of DAH.

Risk HLA class II alleles and amino acid residues in myeloperoxidase-ANCA-associated vasculitis.

A genome-wide association study (GWAS) indicated that myeloperoxidase-ANCA associated vasculitis (AAV) is associated with HLA-DQ. However, susceptibility alleles in these loci have been under-investigated. Here we genotyped 258 Chinese patients with myeloperoxidase-AAV and 597 healthy control individuals at HLA DRB1, DQA1, DQB1 and DPB1, and extracted the encoded amino acid sequences from the IMGT/HLA database. The replication cohort included 97 cases and 107 controls. T cell epitopes of myeloperoxidase were predicted and docked to the HLA molecules. We found DQA1∗0302 (odds ratio 2.34 (95% confidence interval 1.75-3.14)) and DQB1∗0303 (odds ratio 1.89 (1.45-2.48)) were risk alleles for myeloperoxidase-AAV. They are in overt linkage disequilibrium (r2 0.69) and the haplotype DQA1∗0302-DQB1∗0303 presents a significant risk (haplotype score 6.39) as well. Aspartate160 on the DQ α chain (odds ratio 2.06 (1.60-2.67)), encoded by DQA1∗0302, and isoleucine185 on the DQ ß chain (odds ratio 1.73 (1.38-2.18)), encoded by DQB1∗0303, both located in the α2ß2 domains, conferred significant risk for myeloperoxidase-AAV. Homologous modeling showed that DQα∗160D may confer susceptibility to myeloperoxidase-AAV by altering dimerization of the HLA molecules. Thus, more attention should be paid to the roles of amino acids in the α2ß2 domains in addition to the α1ß1 binding groove of HLA class II molecules.

Differences in clinico-pathological characteristics and outcomes between proteinase 3-ANCA positivity and myeloperoxidase-ANCA positivity in lupus nephritis.

BACKGROUND: Owing to the low prevalence of anti-neutrophil cytoplasmic antibodies (ANCA) in lupus nephritis (LN), there is no study about the differences between proteinase 3 (PR3)-ANCA positivity and myeloperoxidase (MPO)-ANCA positivity in LN until now. METHODS: Here we perform a retrospective study to determine whether there are differences in clinic-pathological characteristics and renal outcomes between PR3-ANCA-positive LN patients and MPO-ANCA-positive LN patients. RESULTS: A total of 26 (27.4%) PR3-ANCA-positive LN patients and 69 (72.6%) MPO-ANCA-positive LN patients (p < 0.001) were eligible for this study. Compared with PR3-ANCA-positive LN patients, MPO-ANCA-positive LN patients had significantly higher levels of serum creatinine (109.6 µmol/l vs. 74.3 µmol/l, p = 0.02), lower titers of antinuclear antibodies (ANA) (128 vs. 256, p = 0.01), and higher serum concentrations of C3 and C4 (0.54 g/l vs. 0.36 g/l, p = 0.002; 0.12 g/l vs. 0.06 g/l, p < 0.001; respectively). Furthermore, the MPO-ANCA-positive group had higher scores for chronicity index (p = 0.007), including interstitial fibrosis (p = 0.001) and tubular atrophy (p = 0.03) on biopsy specimens. The renal survival rates for MPO-ANCA-positive LN patients were 94.1% at 1 year, 83.2% at 5 years and 79.6% at 10 years; these values were worse when compared with those of the PR3-ANCA-positive group, which were 100%, 100% and 100%, respectively. CONCLUSION: MPO-ANCA-positive LN patients had more severely impaired baseline renal function and less active lupus serology. More severely chronic pathological changes, including interstitial fibrosis and tubular atrophy on renal specimens, occurred in MPO-ANCA-positive LN patients. We found that MPO-ANCA-positive LN patients had worse renal outcomes.

Rituximab in relapsing and de novo MPO ANCA-associated vasculitis with severe renal involvement: a case series.

BACKGROUND: Antineutrophil cytoplasmic antibody associated vasculitis (AAV) is a group of diseases associated in most cases with the presence of anti-neutrophil cytoplasmic antibodies (ANCAs). Rituximab- based remission induction has been proven effective in ANCA associated vasculitis but scarce data exist in forms with severe renal involvement. In this case series, we report the outcomes in patients with de novo or recurrent MPO-AAV and severe renal involvement treated with rituximab without cyclophosphamide (CYC). METHODS: In this single centre retrospective study, we analysed patients with a clinical diagnosis of de novo or recurrent AAV who met the following criteria: detection of P-ANCA, creatinine clearance lower than 30 ml/min, induction of remission therapy with rituximab without concomitant CYC and a follow up period of at least 6 months. The primary outcomes were complete remission after induction therapy, renal function recovery and mortality after the induction treatment. RESULTS: Eight patients met the inclusion criteria. The M:F ratio was 1:7, the average age was 54 years old and the median follow up was 10 months (7-72); in 2 patients there was a MPA renal limited vasculitis. A renal biopsy was performed in 7 patients. The median BVAS score at rituximab induction was 14(range 6-21). Two patients required haemodialysis before the induction treatment. Four patients developed end stage renal disease (ESRD) that required haemodialysis. These data show a remission of the disease, associated with a stabilization of the kidney function in 50% of patients. In 3 patients who did not show a response, there was also no response to CYC. CONCLUSIONS: This study shows a partial efficacy of rituximab in renal function recovery and a low risk of infectious complications in patients with MPO vasculitis with severe renal involvement, in particular in the short term. The optimal treatment in this subgroup of patients still has to be established because data are lacking.

Microscopic polyangiitis associated with thymic tumor: a case report and review of the literature.

BACKGROUND: Thymic hyperplasia and thymic epithelial tumor (thymoma) have been associated with a variety of autoimmune diseases. Renal involvement has been reported in patients with thymoma. Minimal change disease and membranous nephropathy are frequently observed in glomerular lesions of thymoma patients, but ANCA-associated renal vasculitis is rare. We present a case of thymoma-associated microscopic polyangiitis with positivity for three ANCAs: MPO-ANCA, PR3-ANCA and azurocidin-ANCA. CASE PRESENTATION: An 89-year-old Japanese woman was admitted to our hospital following an episode of general fatigue, nausea, muscle weakness of the lower limbs, and ophthalmoplegia. On urinalysis, proteinuria, hematuria, and cellular casts were observed. Elevated levels of serum creatinine and C-reactive protein were also demonstrated, and MPO-, PR3- and azurocidin-ANCA were detected on serological examination. Renal biopsy showed pauci-immune crescentic glomerulonephritis. We therefore diagnosed rapidly progressive glomerulonephritis due to microscopic polyangiitis. Acetylcholine-receptor antibody was also detected. Chest computed tomography and MRI revealed a lobulated tumor in the anterior mediastinum. We thus also diagnosed myasthenia gravis with thymoma. CONCLUSION: Considering the patient's triple-ANCA positivity, thymic diseases may be associated with the pathogenesis of ANCA-associated vasculitis due to central T-cell tolerance. A further accumulation of cases is needed, because thymectomy does not always induce the remission of thymoma-associated autoimmune diseases.

Global ethnic and geographic differences in the clinical presentations of anti-neutrophil cytoplasm antibody-associated vasculitis.

Objectives: There are few data on clinical profiles of ANCA-associated vasculitis (AAV) in different ethnic populations. The aim of this study was to examine the differences in the ANCA type and clinical features of AAV between populations using the Diagnostic and Classification Criteria in Vasculitis Study (DCVAS) dataset. Methods: The DCVAS is an international, multicentre, observational study recruiting in 133 sites. Eight ethnic categories were analysed: Northern European, Caucasian American, Southern European, Middle Eastern/Turkish, Chinese, Japanese, Indian subcontinent and other. ANCA type was categorized as myeloperoxidase (MPO), PR3 and ANCA negative. Organ system involvement was recorded using a standard dataset. Differences were analysed by chi-squared tests using a Bonferroni correction and logistic regression (adjusting for age and sex). Northern European was the reference population. Results: Data from 1217 patients with AAV were available and the 967 (79.5%) patients recruited by rheumatology departments were analysed to reduce confounding by recruitment specialty. There were differences in ANCA type between ethnic categories (P < 0.001): MPO-ANCA was more common than PR3-ANCA in Japanese, Chinese and Southern Europeans; PR3-ANCA was more common in the other groups. Compared with Northern Europeans, Japanese had a nearly 60-fold increased chance of having MPO-ANCA (vs PR3-ANCA) [odds ratio (OR) 59.2 (95% CI 8.0, 440.7), P < 0.001] and Chinese had a nearly 7-times increased chance [OR 6.8 (95% CI 2.6, 17.8), P < 0.001]. Ophthalmologic and otorhinolaryngologic involvement were less common in Japanese and Chinese populations than Northern Europeans; otherwise, there were few differences in organ involvement between ethnic groups. Conclusion: This study confirms the previously observed differential occurrence of MPO-AAV and PR3-AAV between different ethnic groups.

A multicentre study to improve clinical interpretation of proteinase-3 and myeloperoxidase anti-neutrophil cytoplasmic antibodies.

Objective: The objective of this multicentre study was to improve the clinical interpretation of PR3- and MPO-ANCAs as an adjunct for the diagnosis of ANCA-associated vasculitis (AAV) by defining thresholds and test result intervals based on predefined specificities and by calculating test result interval-specific likelihood ratios (LRs). Methods: Eight different PR3- and MPO-ANCA immunoassays from seven companies were evaluated using 251 diagnostic samples from AAV patients and 924 diseased controls. Results: Thresholds for antibody levels were determined based on predefined specificities (95, 97.5, 99 and 100%) and used to delimit test result intervals. Test result interval-specific LRs were determined. For all assays, the LR for AAV increased with increasing antibody level. For all but one immunoassay, high antibodies levels (associated with LR >55) were found in a substantial fraction (>65%) of patients. The area under the curve (AUC) of receiver operating characteristics analysis of a diagnostic approach in which positive results were confirmed by IIF or another immunoassay was not substantially higher than the AUC of performing immunoassay only. The highest AUC was found when immunoassay was combined with another immunoassay or with IIF. Conclusion: To diagnose AAV based on PR3- and MPO-ANCA, it is useful to define thresholds for antibody levels and to assign test result interval-specific LRs. Higher antibody levels are associated with a higher likelihood for disease. Such information improves clinical interpretation.

Difference in relapse-rate and clinical phenotype by autoantibody-subtype in Japanese patients with anti-neutrophil cytoplasmic antibody-associated vasculitis.

OBJECTIVE: To correlate the serotype specificity to myeloperoxidase (MPO) and proteinase-3 (PR3) with clinical characteristics in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). METHODS: Clinical characteristics and outcomes of patients with AAV in our division from 2005 to 2014 were retrospectively compared on the basis of ANCA subtype. RESULTS: We collected the data from 88 patients with MPO-ANCA vasculitis, and 17 with PR3-ANCA vasculitis. Patients with PR3-ANCA vasculitis were younger, and had higher involvement-rates in the eye, nose, and ear. In both MPO- and PR3-ANCA vasculitis, the most frequently involved organ was the respiratory system. Interstitial pneumonia was more frequent in MPO-ANCA vasculitis (52.3% versus 5.9%, p < 0.01), whereas nodular shadow was more frequent in PR3-ANCA vasculitis (9.1% versus 58.8%, p < 0.01). Multivariable Cox proportional hazard regression analysis showed that the hazard ratio of PR3-ANCA for relapse was 2.48 (95% confidence interval 1.14-5.42, p = 0.02). There was no difference in the survival and the progression to end-stage kidney disease and respiratory failure between the two vasculitides. CONCLUSION: MPO-ANCA vasculitis was a predominant form of AAV in Japan. Classification based on ANCA subtype would be clinically relevant in the prediction of organ involvement and relapse.

First steps in the standardization of immunoglobulin IgG myeloperoxidase-anti-neutrophil cytoplasmic antibody measurements.

The standardization of immunoassays for immunoglobulin (Ig)G myeloperoxidase-anti-neutrophil cytoplasmic antibodies (MPO-ANCA) could contribute to a more accurate diagnosis and follow-up of small vessels-associated vasculitis, a systemic autoimmune disorder that leads to necrosis of blood vessel walls. Despite significant efforts by different groups, the level of comparability of results from commercially available immunoassays used for IgG MPO-ANCA detection is still poor. Therefore, the potential for improvement using reference materials was assessed. The evaluation of a set of 30 patient samples with 11 assays showed that differences between assays result in different interpretations for individual patients. Only 10 of 30 patient samples had the same clinical interpretation among 11 assays applying the cut-off values provided by each respective manufacturer. The correlation between results from 13 different assays was assessed in a pairwise manner. The correlation between results from patient samples was systematically very good for combinations of seven of those assays. The correlation of results ranged from reasonable to good for combinations with four other assays, therefore it should be possible to improve the comparability of results using a commutable reference material for calibration. Feasibility studies were conducted in order to find a reference material format most suitable for a calibrator. Two sets of candidate reference materials were produced from different raw materials, and assessed according to their suitability. A final format was selected, and a candidate reference material was produced.