Objective: The total haemolytic complement activity (CH50) assay evaluates the functioning of the complement system. Accumulating evidence indicates that the activation of the complement system plays a critical role in the pathogenesis of antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Therefore, this study aimed to investigate whether CH50 levels at diagnosis could reflect the baseline activity of AAV. Methods: This retrospective study included 101 immunosuppressive drug-naïve patients with AAV. At diagnosis, all patients underwent clinical assessments for disease activity, including measurement of the Birmingham Vasculitis Activity Score (BVAS) and Five Factor Score (FFS), and laboratory evaluations, such as tests for CH50, C3, and C4 levels. The association between CH50 levels and disease activity was determined. Results: The median BVAS and FFS at diagnosis were 12.0 and 1.0, respectively, whereas the median CH50 level was 60.4 U/mL. There was a negative correlation between the CH50 level and BVAS (r=−0.241; p=0.015). A CH50 cut-off value of 62.1 U/mL was used to classify the patients into two groups: patients with CH50 levels ＜62.1 U/mL (low-CH50 group) and those with CH50 levels ≥ 62.1 U/mL (high-CH50 group). The low-CH50 group had a higher proportion of patients with high disease activity, based on the BVAS, than the high-CH50 group (52.5% vs. 23.8%, p=0.004). Additionally, the low-CH50 group exhibited a lower relapse-free survival rate than the high-CH50 group; however, this difference was not statistically significant (p=0.082). Conclusion Low CH50 levels at diagnosis may reflect high baseline activity of AAV.

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) comprises group of small vessel vasculitides, including granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). In 2022, the American College of Rheumatology (ACR) and the European Alliance of Associations for Rheumatology (EULAR) jointly proposed new classification criteria for AAV (the 2022 ACR/EULAR criteria). In this review, we briefly summarize the 2022 ACR/EULAR criteria for GPA, MPA, and EGPA, and introduce our clinical experience with applying them to patients who were previously diagnosed with AAV based on three criteria: firstly, the classification criteria for GPA and EGPA proposed by the ACR in 1990; secondly, the algorithm for the classification of AAV and polyarteritis nodosa proposed by the European Medicines Agency algorithm in 2007 (the 2007 EMA algorithm); and thirdly, the revised International Chapel Hill Consensus Conference nomenclature of vasculitides in 2012 (the 2012 CHCC definitions). We found that concordance rate was highest in patients with MPA (96.6%), followed by those with EGPA (86.3%) and GPA (73.8%). In addition, compared to previous criteria, we noted several issues of the undervalued or overvalued items in the 2022 ACR/EULAR criteria for classifying AAV and provided several suggestions. To increase the diagnostic accuracy and reduce the discordance rate among the new and previous criteria for AAV, we suggest that the previous criteria should be considered together with the 2022 ACR/EULAR criteria when applying the classification criteria for AAV to patients suspected of AAV.

Purpose: The present study compared the efficacy of mycophenolate mofetil (MMF) with that of azathioprine (AZA) in Korean patients with microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA). Materials and Methods: The medical records of 69 patients with MPA and GPA who received cyclophosphamide and subsequently received AZA or MMF for remission maintenance therapy were reviewed. All-cause mortality, relapse, end-stage renal disease (ESRD), cerebrovascular accident, and cardiovascular disease were evaluated as poor outcomes. Having a lower Birmingham Vasculitis Activity Score (BVAS) was defined as the lowest tertile of BVAS (BVAS ≤11 in this study). Results: In comparative analysis of the occurrence of poor outcomes among patients taking AZA only, MMF only, and MMF after AZA, patients taking MMF only exhibited a significantly lower cumulative ESRD-free survival rate than patients taking AZA only (p=0.028). In terms of ESRD occurrence between the groups based on BVAS at diagnosis, among patients with MPA and GPA with higher BVAS at diagnosis, patients taking MMF only exhibited a significantly lower cumulative ESRD-free survival rate than those taking AZA only (p=0.047). Among patients with MPA and GPA with the lowest tertile of BVAS at diagnosis, cumulative ESRD-free survival rates did not differ. Conclusion With regard to ESRD occurrence, the efficacy of MMF in remission maintenance therapy was less effective than AZA in patients with MPA and GPA. However, among patients with lower BVAS, there was no difference in the occurrence of poor outcomes between patients taking MMF and those taking AZA.

Purpose: The present study compared the efficacy of mycophenolate mofetil (MMF) with that of azathioprine (AZA) in Korean patients with microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA). Materials and Methods: The medical records of 69 patients with MPA and GPA who received cyclophosphamide and subsequently received AZA or MMF for remission maintenance therapy were reviewed. All-cause mortality, relapse, end-stage renal disease (ESRD), cerebrovascular accident, and cardiovascular disease were evaluated as poor outcomes. Having a lower Birmingham Vasculitis Activity Score (BVAS) was defined as the lowest tertile of BVAS (BVAS ≤11 in this study). Results: In comparative analysis of the occurrence of poor outcomes among patients taking AZA only, MMF only, and MMF after AZA, patients taking MMF only exhibited a significantly lower cumulative ESRD-free survival rate than patients taking AZA only (p=0.028). In terms of ESRD occurrence between the groups based on BVAS at diagnosis, among patients with MPA and GPA with higher BVAS at diagnosis, patients taking MMF only exhibited a significantly lower cumulative ESRD-free survival rate than those taking AZA only (p=0.047). Among patients with MPA and GPA with the lowest tertile of BVAS at diagnosis, cumulative ESRD-free survival rates did not differ. Conclusion With regard to ESRD occurrence, the efficacy of MMF in remission maintenance therapy was less effective than AZA in patients with MPA and GPA. However, among patients with lower BVAS, there was no difference in the occurrence of poor outcomes between patients taking MMF and those taking AZA.

Background: We investigated and compared the initial clinical features at diagnosis and the poor outcomes during follow-up in Korean patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) based on sex. Methods: The medical records of 223 immunosuppressive drug-naïve patients with AAV were reviewed. Age, body mass index (BMI), smoking history, AAV subtypes, ANCA positivity, clinical manifestations, Birmingham vasculitis activity score (BVAS), five-factor score (FFS), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) at diagnosis were collected. All-cause mortality, end-stage renal disease (ESRD), cerebrovascular accident (CVA) and cardiovascular disease (CVD) were assessed as the poor outcomes of AAV during follow-up. Results: The median age was 59.0 years and 74 of 223 AAV patients (33.2%) were men.Among variables at diagnosis, male patients exhibited higher BMI than female. However, there were no differences in other demographic data, AAV subtypes, ANCA positivity, BVAS, FFS, ESR and CRP between the two groups. Male patients received cyclophosphamide more frequently, but there were no significant differences in the frequencies of the poor outcomes of AAV between the two groups. Male patients exhibited a significantly lower cumulative patients' survival rate than female patients during the follow-up period based on all-cause mortality (P = 0.037). In the multivariable analysis, both male sex (hazard ratio [HR], 2.378) and FFS (HR, 1.693) at diagnosis were significantly and independently associated with allcause mortality during follow-up. Conclusion Male sex is a significant and independent predictor of all-cause mortality in AAV patients.

Background: We investigated and compared the initial clinical features at diagnosis and the poor outcomes during follow-up in Korean patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) based on sex. Methods: The medical records of 223 immunosuppressive drug-naïve patients with AAV were reviewed. Age, body mass index (BMI), smoking history, AAV subtypes, ANCA positivity, clinical manifestations, Birmingham vasculitis activity score (BVAS), five-factor score (FFS), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) at diagnosis were collected. All-cause mortality, end-stage renal disease (ESRD), cerebrovascular accident (CVA) and cardiovascular disease (CVD) were assessed as the poor outcomes of AAV during follow-up. Results: The median age was 59.0 years and 74 of 223 AAV patients (33.2%) were men.Among variables at diagnosis, male patients exhibited higher BMI than female. However, there were no differences in other demographic data, AAV subtypes, ANCA positivity, BVAS, FFS, ESR and CRP between the two groups. Male patients received cyclophosphamide more frequently, but there were no significant differences in the frequencies of the poor outcomes of AAV between the two groups. Male patients exhibited a significantly lower cumulative patients' survival rate than female patients during the follow-up period based on all-cause mortality (P = 0.037). In the multivariable analysis, both male sex (hazard ratio [HR], 2.378) and FFS (HR, 1.693) at diagnosis were significantly and independently associated with allcause mortality during follow-up. Conclusion Male sex is a significant and independent predictor of all-cause mortality in AAV patients.

Objective: This study retrospectively reviewed the process of classifying antineutrophil cytoplasmic antibody (ANCA)-negative granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) in a cohort of patients with ANCA-associated vasculitis (AAV), and investigated the association between recurrent idiopathic cutaneous leukocytoclastic angiitis and ANCA-negative MPA. Methods: The medical records of 242 patients with AAV were retrospectively reviewed. Of 49 patients with ANCA-negative AAV, 24 patients with ANCA-negative eosinophilic GPA (EGPA) were excluded, because ANCA positivity or negativity is not critical in classifying EGPA. Ultimately, 25 patients with ANCA-negative GPA and MPA were analysed in this study. The classification of GPA and MPA were based on the 2007 European Medicines Agency algorithm for AAV. Results: The median age of patients with ANCA-negative GPA and MPA was 54.0 years and 24% were male. Of the 25 patients without ANCA, 8 patients were classified as GPA and 17 as MPA. Eight patients with ANCA-negative GPA were easily confirmed as definitive GPA. Fourteen of the 17 patients ANCA-negative MPA were classified as MPA based on histological features suggestive of AAV without granuloma formation and the absence of surrogate markers for GPA. Meanwhile, three of the patients that were ANCA-negative exhibited only recurrent idiopathic cutaneous leukocytoclastic angiitis without other major organs affected and thus were classified as possible MPA. Within one year, they were classified as definitive MPA based on ANCA positivity and/or renal histology. Conclusion Recurrent idiopathic cutaneous leukocytoclastic angiitis may be associated with ANCA-negative MPA in patients who exhibit cutaneous necrotising vasculitis.