MO303URINARY ALBUMIN-TO-CREATININE RATIO INDICATES NECROTIZING AND CRESCENTIC GLOMERULONEPHRITIS IN ANCA-ASSOCIATED VASCULITIS

Abstract

\n \n \n Renal involvement is a common and severe complication of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) as it can cause acute kidney injury (AKI), end-stage renal disease (ESRD) or death. We have previously reported that elevated urinary albumin-to-creatinine ratio (uACR) correlates with rapid deterioration of kidney function in ANCA GN. Therefore, we here aimed to describe the association between proteinuric findings and histopathological diagnosis of necrotizing and crescentic ANCA GN in 50 urinary samples at admission and corresponding renal biopsies of patients with AAV.\n \n \n \n A total number of 50 urinary samples at admission and corresponding renal biopsies with confirmed renal involvement of AAV were retrospectively included between 2015 till 2020 in a single-center observational study.\n \n \n \n Renal involvement of AAV revealed variable proteinuria ranging from low-range to nephrotic syndromes, however most patients presented with subnephrotic proteinuria predominated by albumin (uACR). Severely increased uACR levels >300 mg/g correlated with reduction of normal glomeruli (P<0.001), attributed to increased glomerular crescents (P<0.001) and necrosis (P=0.008). By contrast, no such association was observed for global sclerotic glomeruli (P=0.58), revealing that uACR reflects necrotizing and crescentic ANCA GN rather than adaptive glomerular hyperfilitration in chronic sclerosing stage. These findings were additionnaly bolstered by histopathological subgrouping and ARRS: patients with uACR levels >300 mg/g were classified either into Berden’s crescentic class (P=0.002) or ANCA renal risk score (ARRS) high/intermediate risk (P=0.003). No association between uACR levels and extrarenal manifestation of AAV disease could be observered, suggesting that uACR levels reflected specific renal involvement with ANCA GN and further confirmed by survival analysis for cumulative incidence of RRT during the short-term course of disease. In summary, uACR measurements at admission were associated with renal biopsy findings thereafter. Levels of uACR >300 mg/g were more frequently observed in necrotizing and crescentic ANCA GN with classification either into Berden’s crescentic class or ARRS high/intermediate risk and specific for renal involvement in AAV.\n \n \n \n Early identification of patients who mostly benefit from aggressive immunosuppressive therapy is of clinical importance. Our observation that uACR levels at disease onset predict necrotizing and crescentic ANCA GN requires further investigation for therapeutic decision especially in patients with severe deterioration of kidney function.\n