After transplantation, allograft rejection poses the most significant risk to graft survival, leading to mortality, morbidity, and decreased quality of life. The current gold standard for diagnosing rejection involves invasive and costly tissue biopsies, which can be subject to interpretation errors. While various biomarkers offer less invasive alternatives with reduced risk and greater convenience, their sensitivity and specificity may vary. The emergence of donor-derived cell-free DNA (dd-cfDNA) as biomarker for graft injury represents a promising breakthrough in diagnosing post-transplantation allograft injuries. dd-cfDNA, released by the allograft into the recipient's bloodstream post-transplant, increases in cases of injury, rejection, or malfunction. Genetically distinct from the recipient's own cfDNA, dd-cfDNA can be quantified at low levels, making it an effective biomarker for post-transplant surveillance.
This study evaluates the effectiveness of AlloSeq cfDNA, a decentralized, NGS-based testing kit, compared to the established standard, AlloSure Kidney, to enhance allograft rejection monitoring. Kidney transplant recipients (n=580) from 3 referral centers underwent measurements (603 total evaluations) with AlloSeq cfDNA and AlloSure Kidney dd-cfDNA measurements alongside allograft biopsies. Correlation between assays was evaluated using r-squared (r2) and Spearman’s rank correlation test, and associations with rejection using logistic regression analyses. Mean dd-cfDNA levels from AlloSeq cfDNA and AlloSure Kidney were 0.51 ± 0.81% and 0.43 ± 0.78%, respectively. The assays were highly correlated, with r2 = 0.95 and Spearman’s rank correlation 0.88 (p-value < 0.0001). Mean dd-cfDNA levels were 1.15 ± 1.60% with and 0.39 ± 0.48% without rejection (p < 0.0001) for AlloSeq cfDNA, and 1.06 ± 1.47% with and 0.31 ± 0.49% without rejection (p < 0.0001) for AlloSure Kidney.
Both tests showed significant association with allograft rejection (p < 0.0001). Additionally, consistency between the assays was confirmed across various clinical scenarios, including post-transplant timepoint, allograft stability, and different rejection subcategories (antibody-mediated, T-cell mediated, or mixed rejection). The AlloSeq cfDNA assay provides precise results within 24 hours, requiring minimal input and offering flexibility suitable for centers of all sizes. This ensures convenience in clinical practice and enhances patient care.