#3734 Predictors of kidney outcomes in ANCA-associated vasculitis: a retrospective cohort study

Abstract Background and Aims ANCA-associated vasculitis (AAV) is characterized by small vessel inflammation with kidney involvement being a major determinant of outcomes. This study aimed to evaluate clinical and serological parameters at diagnosis and their association with kidney outcomes at 6 and 24 months of follow-up. Method This retrospective cohort study included adult patients with ANCA-associated vasculitis who were followed at a tertiary center between 2000 and 2018. Demographic, clinical, and laboratory data were collected at diagnosis and at 6 and 24 months. Patients were excluded if they lacked baseline positive ANCA serology or if records of follow-up proteinuria and estimated glomerular filtration rate (eGFR) were missing. Patients were divided according to proteinuria (higher or lower 0.5 g/G) and kidney function (eGFR higher or lower than 45 mL/min/1.73 m²). Results Twenty-six patients were included in the study. Comorbidities included hypertension (38.5%), dyslipidemia (42.3%), and chronic kidney disease (26.9%). At the time of diagnosis, median GFR was 19.0 mL/min/1.73 m² (IQR 20.00), serum creatinine 2.87 mg/dL (IQR 2.60), proteinuria 0.70 g/G (IQR 1.16) and microscopic hematuria was present in 88.5% of patients. Clinical manifestations included ear-nose-throat (ENT) involvement (38.5%) and alveolar hemorrhage (23.1%). MPO-ANCA were present in 84.6% of patients, while 15.4% had PR3-ANCA. During follow-up, 83.3% became ANCA-negative and 24.0% showed recurrent positivity. After treatment, most patients (n = 18, 69.2%) did not require kidney replacement therapy (KRT). Five patients (19.2%) died. Patients with higher proteinuria at 6 months showed significantly higher baseline creatinine (P = 0.0012), PR3 levels (P = 0.029), and lower GFR (P = 0.016). At 24 months, only baseline creatinine remained significantly higher in the proteinuria ≥0.5 g/d group. Binary logistic regression identified lower GFR at diagnosis was associated with higher proteinuria at 6 months (Or = 0.923; P < 0.05), while higher creatinine at 6 months was associated with higher odds of proteinuria at 24 months (Or = 2.388; P < 0.05). MPO levels at diagnosis were significantly higher in patients with eGFR ≤45 mL/min/1.73 m² at both 6 months and 24 months. This tendency was also observed at 6 months with MPO levels associating with lower eGFR at 24 months. Conclusion Our study demonstrates that in ANCA-associated vasculitis, baseline kidney function significantly impacts long-term outcomes, particularly regarding the levels of proteinuria and eGFR. The identification of baseline eGFR and 6-month creatinine as independent predictors of persistent proteinuria highlights the importance of early kidney function in determining disease trajectory. Despite significant kidney involvement at presentation, the majority of patients avoided KRT, suggesting effective response to standard therapeutic approaches.