Abstract
Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) are a group of multisystemic autoimmune diseases characterized by necrotizing inflammation of small vessels, with a predilection for the kidney. The prognostic value of histological classification of ANCA-glomerulonephritis (ANCA-GN) is discussed. In 2010, Berden and colleagues proposed a prognostic classification based on glomerular involvement; in 2018, Brix et al. introduced the ANCA Renal Risk Score, which includes histological features and glomerular filtration rate; in 2017 the Mayo Clinic Chronicity Score, that considers chronic histological lesions, was designed and assessed in ANCA-GN. We aimed to identify which score is the best tool to predict end-stage kidney disease or death in a cohort of ANCA-GN patients.
Patients who underwent kidney biopsy in two Italian centers within 32 years were retrospectively collected. Inclusion criteria: age >18 years, and at least one year of follow-up. A minimum of 10 glomeruli was considered adequate for a biopsy. Renal biopsies were classified according to Berden's classification, Renal Risk Score and Mayo Clinic Chronicity Score. The primary end point of the study was the development of end-stage kidney disease (ESKD) at 5 years, defined as the chronic need of renal replacement therapy (RRT) or glomerular filtration rate (GFR) <15 ml/min. The secondary endpoint was a composite endpoint of ESKD or death for all causes.
Of the 152 patients 84 were male, the median age was 63.8 years (Figure 1). Mean eGFR at diagnosis was 21.32 ml/min/1.73 m2. 32.2% of patients were PR-3 positive, 50.6% were MPO positive, 17.2% were ANCA-negative. After a mean follow-up of 71.7 ± 66.7 months, 59 patients (38.8%) were on chronic dialysis or with a GFR <15 ml/min; among them, 20 patients died. The pure kidney survival rate (without ESKD or GFR<15 ml/min) was 79% at 1 year, 65% at 5 years, 59.8% at 10 years. Figure 2 reported the pure kidney survival rates of the patients assigned to every class of the three scores that we considered in this study. Fig. 3, Fig. 4, Fig. 5 show Kaplan-Meyer curves for the secondary outcome (ESKD+death); patients are classified according to the Berden's score (Fig. 2), the Renal Risk Score (Fig. 3) and Mayo Clinic Chronicity Score (Fig. 4).
Berden histopathological classification and Renal Risk Score are predictive of renal prognosis when we consider the primary outcome (ESKD or eGFR<15 ml/min) and when we consider the composite outcome (ESKD + death). The Mayo Clinic Chronicity Score allows a reliable stratification of the patients only when we consider the composite outcome (ESKD and death).
IQR; interquartile range. SD; standard deviation.
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