Update on diagnostic and therapeutic strategies for antibody-mediated rejection in kidney transplantation

Table 4 Comparison of clinical utility of blood vs urine biomarkers in kidney transplant monitoring

Feature	dd-cfDNA	Urinary CXCL10
Sample type	Peripheral blood	Urine
Target	Fragmented donor DNA from injured graft	Chemokine linked to immune activation
Clinical role	Detects active graft injury and acute rejection	Predicts and monitors acute rejection, especially AMR
Sensitivity/specificity	About 59% sensitivity, about 85% specificity at 1% threshold	High NPV for ruling out rejection
PPV/NPV	PPV: 61%, NPV: 84%	NPV: High; PPV varies
Timing of detection	Early detection due to short half-life (about 30 minutes)	Reflects ongoing inflammation; may lag behind dd-cfDNA
Regulatory status	FDA-approved; reimbursed by Medicare	Research-stage; not yet standardized
Cost	About 2800 dollars per test	About 100-300 dollars per test
Advantages	High specificity; validated in multicenter trials	Noninvasive, inexpensive, easy to collect repeatedly
Limitations	Costly; may be affected by other injuries	Limited standardization; influenced by urine concentration
Use in subclinical rejection	Useful when combined with other assays (e.g., TruGraf)	Promising but less validated for subclinical cases

dd-cfDNA: Donor-derived cell-free DNA; CXCL10: C-X-C motif chemokine 10; AMR: Antibody mediated rejection; NPV: Negative predictive value; PPV: Positive predictive value; FDA: Food and Drug Administration.