VALIDATION OF AN ANCA ASSOCIATED VASCULITIS RENAL RISK SCORE IN THE SOUTH WEST OF ENGLAND

Abstract Background and Aims Determining the renal prognosis for patients with ANCA associated vasculitis (AAV) is important in guiding treatment decisions, including balancing the risks and benefits of aggressive immunosuppression, and informing patients of their likely trajectory. We examined the performance of the clinicopathologic risk stratification tool developed by Brix et al. 1 in determining renal outcomes in a cohort of AAV patients in the South West of England. Method A retrospective review of case notes of patients diagnosed with AAV between 2010 and 2020 from two renal units (Bristol and Plymouth) was performed. Patients were followed up until 1st August 2020. Demographic details, kidney function at presentation and initial treatment regime were collected alongside kidney biopsy data. The renal risk score divides patients into three groups determined as being at low, medium and high risk of adverse renal outcomes based on (1) the percentage of normal glomeruli on kidney biopsy, (2) the percentage of tubular atrophy and interstitial fibrosis on kidney biopsy and (3) eGFR at diagnosis. The outcome of interest was the development of end stage kidney disease (ESKD), defined as a dialysis requirement >3months or kidney transplantation. Patients were censored for death. Results In total 93 individuals were diagnosed with AAV over the study period; 51% were female and the median age at diagnosis was 69 years [IQR 60-78]. ANCA subclass was MPO positive in 73% of cases, PR3 positive in 19% and ANCA negative in 8%. At presentation, 42% had an eGFR below 15ml/min/1.73m2. With respect to risk scores, 17% of individuals were low risk (n=16), 52% were medium risk (n=48) and 31% were high risk (n=29). Median follow up was 3.2 years [IQR 1.3-5.9], over which time 18% of patients developed ESKD (1 in the low risk group, 7 in the medium risk group and 9 in the high risk group). A further 20% of patients died. A Kaplan-Meier survival curve (Figure 1) demonstrated worsening renal survival with rising risk group (Log-rank test, p=0.05). At 1 year, 74 patients (80%) were alive and in these individuals renal survival was 100% in the low risk group, 91% in medium risk group and 75% in the high risk group. Conclusion Overall, 18% of patients developed ESKD over a median follow up of 3.2 years. The renal risk score developed by Brix et al. helps prognosticate renal survival and may assist in shared decision making with patients regarding treatment options. The score demonstrates the importance of the degree of chronicity in determining renal survival. Further work in larger cohorts to compare the performance of the risk score in different subgroups of patients with AAV would be informative.