222. ANCA (+) vasculitis: value of urinary biomarkers in distinguishing active disease

Background: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a chronic relapsing and remitting disease and a cause of rapidly progressive glomerulonephritis. CD163 and calprotectin have been proposed as biomarkers of active renal vasculitis. The objective of this study was to determine if serum and urine (s/u)calprotectin and urine (u)CD163 are disease activity and prognosis biomarkers in ANCA vasculitis. Methods: We included 179 patients diagnosed with ANCA vasculitis (n= 73 acute phase, n=106 in remission) and 4 healthy controls. We collected serum and urine at the time of inclusion. We determined the serum and urinary concentration of calprotectin and urinary CD163 using Enzyme Linked Immunoassay (ELISA). We compared the concentrations of biomarkers between groups using the Mann Whitney U test. We plotted the ROC curve of each biomarker to assess its ability to discriminate disease activity. We elaborated a combining biomarker model using the recursive partition method and we presented the result in the form of a decision tree. Results: The concentration of sCalprotectin and uCD163 was higher in patients in the acute phase compared to patients in remission (p<0,0001 and 0,0013, respectively). We did not find differences regarding the concentration of uCalprotectin. We evaluated the ROC curves of the different biomarkers to determine the detection of disease activity and we observed that sCalprotectin and uCD163 were good biomarkers to discern activity [0,712 (0,62-0,80), p