Combined Biomarker Approach Using Extracellular Vesicles, Donor-Derived Cell-Free DNA, and Donor-Specific Antibodies for Monitoring Renal Allograft Function: A Narrative Review

Background and Objectives: Renal transplantation is the optimal treatment for end-stage renal disease, yet long-term allograft survival remains threatened by immune-mediated injury and chronic nephropathy. Conventional monitoring using serum creatinine and protocol biopsy suffers from limited sensitivity for early, subclinical injury. Liquid biopsy-based biomarkers offer a non-invasive alternative. Materials and Methods: We conducted a systematic narrative review of studies published between January 2010 and December 2024, identified through PubMed, Scopus, and Web of Science. Results: Extracellular vesicles carry injury-specific molecular cargo reflecting the biological state of tubular, glomerular, and endothelial cells; urinary EV CXCL9 protein and exosomal CD3ε mRNA have demonstrated AUC values of 0.81–0.88 for detection of T-cell-mediated rejection. Donor-derived cell-free DNA quantifies global graft cell death; the FDA-cleared AlloSure assay achieves AUC 0.74 and NPV 84% at the validated ≥1.0% threshold established in the DART trial. Donor-specific antibodies—particularly complement-fixing C1q-positive DSA—confer markedly inferior 5-year graft survival compared with DSA-negative recipients (54% versus 93%). Multi-biomarker panels integrating all three modalities yield AUC 0.88–0.94 and NPV 91–95%. Conclusions: The integration of EV, ddcfDNA, and DSA monitoring into a unified surveillance framework offers a clinically meaningful advance over creatinine-based monitoring. Prospective randomized trials confirming improvement in long-term allograft survival will be the critical next step.