Background and Aims Outcomes in ANCA vasculitis remain difficult to predict and therapeutic decision-making can be challenging. We aimed to establish if a renal risk score (RRS) could predict outcomes in this population. Method The Scottish Renal Biopsy Registry is a complete national dataset of all renal biopsies performed in Scotland. Those who had a first renal biopsy between 01/01/2014 and 31/12/2017 with evidence of ANCA vasculitis were included. Demographic data, treatment regimens, episodes of relapse and patient and kidney survival were recorded, retrospectively. The RRS was calculated using the system proposed by Brix et al (1). Each patient was categorised according to % of normal glomeruli (N0 >25%, N1 10 to 25%, N2 <10%), % of tubular atrophy/interstitial fibrosis (T0 ≤25%, T1 >25%) and eGFR (CKD-EPI) at time of biopsy (eGFR: G0 >15 mL/min/1.73 m2, G1 ≤15 mL/min/1.73 m2). Individual scores were summated and patients defined as low, medium or high risk. Cox proportional hazard models were created for survival to ESKD, relapse and death, stratified by risk category. Analyses were conducted using R statistical software. Results Two-hundred and forty-six patients with biopsy proven ANCA vasculitis were identified. Fifty percent (n=123), 46% (n=112) and 5% (n=11) were stratified as low, medium and high risk respectively. Fifty-two percent (n=129) were male and mean age at biopsy was 66.7±12.2 years. This was similar across the risk categories. Mean eGFR was lower in the high-risk category (High risk 8.6±6.1 ‘v’ Low risk 45.7±26.0 ml/min/1.73m2, p<0.001) and proteinuria was higher (High risk 405 (IQR 170-767) ‘v’ Low risk 81 (IQR 41-155) mg/mmol, p<0.001). Thirty-seven percent (n=91) were PR3 antigen positive, 2% (n=5) had dual positivity. In the high risk category, 8 (73%) were PR3 or dual positive. Eighteen (n=7%) patients experienced pulmonary haemorrhage; representation similar across all risk categories. Those categorised as medium or high risk were more likely to receive plasma exchange and/or haemodialysis at presentation (p<0.001) compared with the low risk category. Overall, 16% (n=40) of patients relapsed with a trend to higher risk of relapse in the low risk group (27% of these patients, p=0.05). Thirty seven (15%) patients developed ESKD. Cox proportional hazard model for development of ESKD (Figure 1) shows that those in high risk ‘v’ low risk category were more likely to reach ESKD (HR 124.8, 95% CI 26.4-590.3, p<0.001). Patient survival was similar between risk categories. Conclusion A simple RRS, using routinely reported data, in patients with renal biopsy proven ANCA vasculitis can help to predict development of ESKD. It may also be predictive of future relapse in those with a lower RRS, most likely explained by reduced irreversible damage in this group. The RRS could inform monitoring and treatment decisions. Whilst the numbers are small, a unique strength of this data is that it is based on a complete national dataset making it less susceptible to bias from regional variations in diagnostic and therapeutic practice.
Background and Aims Seasonal variation of ANCA associated vasculitis (AAV) and a possible link to extrinsic infective triggers is predominantly based on single centre epidemiological data. Despite frequent confounding factors including difficulty in identifying the precise time of disease onset, seasonality may be associated with the type of vasculitis and may impact the incidence of renal involvement. Therefore, the aim of this study was to explore if there is an association between seasonality, severity and incidence of biopsy-proven renal vasculitis in the Scottish population. Method Using the Scottish renal biopsy registry, we identified all adult native renal biopsies performed across Scotland between 2014 and 2018 with a diagnosis of AAV, including microscopic polyangiitis (MPA) and granulomatosis with polyangitis (GPA). Demographic data including ANCA antibody status, histological diagnosis, estimated glomerular filtration rate (eGFR) and proteinuria at presentation were recorded. Seasons were defined as autumn (September – November), winter (December-February), spring (March – May) and summer (June - August). Statistical analysis was performed using multivariate ANOVA analysis and Student’s t-test in parametric data. Results 339 cases of biopsy proven AAV were identified and included in the analysis. In this cohort, 53% were female with mean patient age of 65.6 years (± 13). Mean estimated glomerular filtration rate (eGFR) at the time of diagnosis of AAV was 32 (± 27.2) mL/min/1.73m2 and median urinary protein creatinine ratio (uPCR) was 146mg/mmol (IQR 79.8 – 271.3). Diagnosis of MPA n=209(62%) was more common than GPA n=130(38%) and patients with MPA were significantly younger at presentation (63.5 ± 13.6 ‘vs’ 67 ± 12.7 years, p = 0.017). Otherwise, these groups did not differ in mean eGFR (MPA 29.6 ± 25.7 ‘vs’ GPA 34.8 ± 27.6 mL/min/1.73m2) or median uPCR (MPA 147, IQR 78.6 – 286.5 ‘vs’ GPA 139, IQR 80.5 – 261 mg/mmol) at onset. We observed a mean of 3.5 (± 1) new cases of MPA and 2.1 (± 0.7) new cases of GPA per month, with no significant difference observed in month-to-month comparison. Seasonal analysis showed mean occurrence of 11.4 (± 4.5) cases of MPA in autumn, 11.2 (± 4.9) in winter, 10.6 (± 1.5) in spring and 8.6 (± 1.9) in summer months. In GPA, mean 6.6 (±2.7) cases occurred each autumn, 5.4 (± 3) in winter, 7.2 (± 2.9) in spring and 6.4 (± 0.9) in summer months. Overall, no significant differences in monthly or seasonal incidence across 5 years of monitoring were detected. Similarly, we observed no difference in renal function at presentation during different seasons for MPA (mean eGFR range 21.8 – 37.6 mL/min/1.73m2, uPCR median range 112 – 167.5 mg/mmol) or GPA (mean eGFR range 32-37 mL/min/1.73m2; uPCR median range 110 – 244 mg/mmol). Conclusion Our data suggest that there is no seasonal variation in the incidence of AAV diagnosed on kidney biopsy in patients living in Scotland. Additionally, patients present with similar levels of kidney function regardless of season. Thus traditional holiday periods i.e. Easter/Christmas do not seem to lead to a delay in diagnosis. This is the first study to consider seasonality in a complete national cohort and suggests that seasonal extrinsic factors do not play a major role in the pathogenesis leading to AAV onset.
SUMMARY: The kidney may be involved in several forms of systemic vasculitis, particularly those affecting small‐calibre blood vessels. Hence, the majority of cases involve patients with Wegener's granulomatosis, Churg‐Strauss syndrome or microscopic polyangiitis. Anti‐neutrophil cytoplasmic antibodies (ANCA) are found in the majority of these patients and their detection has increased the sensitivity and specificity of diagnosis. However, the role of ANCA in the pathogenesis of these lesions remains uncertain. Moreover, the approach to treatment, both in terms of induction and maintenance of remission, remains problematic. This brief review discusses aspects of ANCA and current approaches to management.
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