Biomarkers Detecting the Activity of ANCA-Associated Vasculitis: A Systematic Literature Review

Introduction: Anti-neutrophil cytoplasmic antibody (ANCA)–associated vasculitis (AAV) encompasses a group of rare systemic autoimmune diseases characterized by inflammation of small- and medium-sized blood vessels. Despite the efficacy of immunosuppressive therapy in achieving disease remission, a significant proportion of patients experience relapses, underscoring the need for reliable biomarkers to monitor disease activity. This systematic literature review evaluates the potential of urinary and serum biomarkers (CD163, CD206, CD25, and MCP-1) to detect active AAV in adult patients. Method: A comprehensive search on PubMed, Embase, and Cochrane databases identified relevant studies, which were screened and assessed for inclusion based on predefined criteria. Data extraction and quality appraisal were independently conducted using the Quality Assessment Tool for Diagnostic Accuracy Studies (QUADAS-2). Results: A total of 20 studies evaluated biomarkers for their diagnostic accuracy in detecting AAV activity. Most articles were scored as moderate risk of bias, with low concerns regarding applicability. Urinary soluble CD163 shows promising diagnostic accuracy for active renal vasculitis, with sensitivity and specificity values ranging from 0.72 to 1 and 0.67 to 0.98, respectively. Serum soluble CD163 and CD206 demonstrated variable accuracy. Serum MCP-1 did not differ between patients in remission and patients with active disease, while urinary MCP-1 showed potential but with inconsistent results across studies. Serum soluble CD25 was significantly elevated in active disease. Some combinations of biomarkers improved diagnostic performance (usCD163 + usCD25 + ssCD25 and usCD163 + serum Calprotectin + hematuria). Conclusion: In conclusion, while usCD163 individually appears to be the most reliable single biomarker for detecting active renal vasculitis in these studies, the heterogeneity of study designs and cutoff values across studies precludes definitive conclusions. Further research is necessary to standardize biomarker use, evaluate promising biomarker combinations, and improve the accuracy of activity monitoring both in renal and extrarenal AAV.