Urinary Soluble CD163 and Disease Activity in Biopsy-Proven ANCA-Associated Glomerulonephritis

Background and objectives ANCA-associated GN is a common cause of rapidly progressive GN, with high relapse rates. The early recognition of an ANCA-associated GN relapse is of importance to prevent loss of kidney function. Urinary soluble CD163 has been identified as a promising marker of active ANCA-associated GN. Previous studies, however, are limited by the lack of histologic data. Design, setting, participants, & measurements We analyzed urinary soluble CD163 in 95 patients with ANCA-associated vasculitis who underwent a kidney biopsy. In total, 125 kidney tissue sections (first kidney biopsy, n=67; repeated biopsy, n=58) with concurrent 24-hour urine samples were studied. Correlation analyses comparing urinary soluble CD163 levels and morphologic features of ANCA-associated GN were performed using Spearman rank correlation analysis. The diagnostic performance of biomarkers to detect relapsing ANCA-associated GN was evaluated using receiver operating characteristics curve analysis. Results High levels of urinary solubleCD163were found in 96 (87%) of 110 biopsieswith active ANCA-associated GN compared with one (7%) of 15 biopsies without active ANCA-associated GN and one (6%) of 17 healthy controls. Urinary soluble CD163 correlated with fibrinoid necrosis (Rho=0.48, P