Anti-ETAR and suPAR as markers of disease activity in renal ANCA-associated vasculitis

Abstract

Purpose: In anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), there is a lack of reliable biomarkers of disease activity. The aim of the study was to evaluate soluble urokinase plasminogen activator receptor (suPAR) and anti-endothelin-1 type A receptor (anti-ETAR) antibodies levels in active phase and remission of AAV.

Patients and methods: We enrolled 60 patients (median age 63.0 years) with renal AAV into this study. Plasma suPAR, urine suPAR (expressed as urine suPAR/creatinine ratio) and serum anti-ETAR antibodies were assayed by ELISA. Disease activity was assessed using Birmingham Vasculitis Activity Score (BVAS) and patients were divided into 2 subgroups based on their BVAS scores, namely: active AAV subgroup (BVAS≥1) and remission subgroup (BVAS ​= ​0). Median follow-up was 12 months.

Results: Patients with active AAV had higher levels of all candidate biomarkers in comparison to those in remission (p ​< ​0.05). C-statistics for plasma suPAR, urine suPAR/creatinine ratio and serum anti-ETAR were 0.807, 0.713 and 0.783, respectively. In multivariable analysis, no clear associations were found between serum anti-ETAR and BVAS, while both plasma suPAR and serum anti-ETAR were independently influenced by estimated glomerular filtration rate (eGFR).

Conclusions: Plasma suPAR better discriminated between active AAV and remission in comparison to urine suPAR/creatinine ratio and serum anti-ETAR antibodies.

Keywords: ANCA; Kidney; Vasculitis; suPAR.