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

Table 3 Limitations of biomarkers and their validation status

Biomarker/test	PPV	NPV	Estimated cost	Validation status
dd-cfDNA (> 1%)	61%	84%	About 2800 dollars per test	FDA-approved; medicare reimbursed
kSORT (17-gene PCR panel)	92% (sensitivity)	93% (specificity)	Not commercially available	Research-stage; limited clinical use
TruGraf v1	Combined PPV/NPV with dd-cfDNA	Improved detection	About 2000-2500 dollars per test	Validated in stable graft recipients
Peripheral blood GEP	47%	82%	About 1500-2000 dollars	Clinically available; moderate uptake
ELISPOT (IFN-γ)	Variable	Variable	High (labor-intensive)	Limited scalability; research use
Urinary CXCL10	Moderate	Moderate	Low (about 100-300 dollars)	Research-stage; promising results
Urinary miRNAs	Variable	Variable	Moderate (about 500-1000 dollars)	Experimental; under validation
MMDx	64%	91%	About 3000-4000 dollars per biopsy	Validated; used in specialized centers
Banff transcript panel	Not yet published	Not yet published	TBD	Under evaluation by Banff committee

PPV: Positive predictive value; NPV: Negative predictive value; cfDNA: Cell free DNA; FDA: Food and Drug Administration; kSORT: Kidney Solid Organ Response Test; PCR: Polymerase chain reaction; GEP: Gene expression profiling; ELISPOT: Enzyme linked immuno spot; IFN: Interferon; CXCL10: C-X-C motif chemokine 10; miRNAs: MicroRNAs; MMDx: Molecular Microscope Diagnostic System; TBD: To be determined.