AB0400\u2005URINARY ALBUMIN-TO-CREATININE RATIO INDICATES NECROTIZING AND CRESCENTIC GLOMERULONEPHRITISIN ANCA-ASSOCIATED VASCULITIS

Abstract

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.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.Renal involvement of AAV revealed variable proteinuria ranging from low-range to nephrotic syndromes, however most patients presented with subnephrotic proteinuria. Severe deterioration of kidney function requiring RRT within 30 days after admission was associated with elevated levels of nonselective proteinuria, mostly attributed to albuminuria (uACR). Because we have previously shown that histologically confirmed ANCA GN with glomerular crescents and necrosis is associated with AKI and requirement of RRT during short-term disease course and elevated uACR levels were equally associated with AKI and requirement of RRT during the short-term course after disease onset, we next analyzed the association between uACR measurements at admission and histopathological findings within renal biopsies performed thereafter. Severely increased uACR levels >300\u2009mg/g correlated with reduction of normal glomeruli, attributed to increased glomerular crescents and necrosis. By contrast, no such association was observed for global sclerotic glomeruli, revealing that uACR reflects crescentic ANCA GN rather than adaptive glomerular hyperfilitration in chronic sclerosing stage. Since uACR levels could reflect both, either a specific renal involvement with necrotizing and crescentic ANCA GN or severity of systemic AAV disease, we next correlated uACR levels assessed at admission with extrarenal disease manifestation. We observed no association between uACR levels and extrarenal manifestation of AAV disease including pulmonary hemorrhage, skin involvement and BVAS assessment, suggesting that uACR levels reflected specific renal involvement in AAV. These observations were further confirmed by survival analysis for cumulative incidence of RRT during the short-term course of disease.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.None declared