Donor‐Derived Cell‐Free DNA for Diagnosing Subclinical Rejection: A Pilot Multicenter Study in Japanese Living‐Donor Kidney Transplantation
Toshihito Hirai, Taro Banno, Kazuya Omoto, Tomokazu Shimizu, Sumi Hidaka, Yu Kijima, Miyuki Furusawa, Ayaka Saitoh, Kohei Unagami, Masashi Inui, Hideki Ishida, Toshio Takagi
Abstract
BACKGROUND: Donor-derived cell-free DNA (dd-cfDNA) offers a non-invasive biomarker for detecting allograft injury. However, its performance in predominantly living-donor transplant settings in Asian populations remains underexplored. METHODS: In a multicenter prospective pilot study, 73 living-donor kidney transplant (LKT) recipients from Japan underwent plasma dd-cfDNA testing and protocol biopsies approximately 1 year post-transplant. Diagnostic performance of dd-cfDNA for subclinical antibody-mediated rejection (AMR) was evaluated at 1.0% and 0.5% cut-off thresholds. RESULTS: Eight patients (11.0%) were diagnosed with subclinical active AMR. Patients with dd-cfDNA ≥1.0% showed significantly higher incidence of AMR compared to those with dd-cfDNA <1.0% (80% vs. 5.9%, p < 0.001). ROC analysis revealed an AUC of 0.85 for dd-cfDNA in diagnosing AMR. Lowering the threshold to 0.5% improved sensitivity while maintaining high specificity. Patients with persistent donor-specific antibodies (DSA) at 1-year follow-up exhibited significantly higher dd-cfDNA levels. Neither HLA nor ABO incompatibility nor donor-recipient relation significantly affected dd-cfDNA levels. CONCLUSION: dd-cfDNA demonstrates high negative predictive value and complements DSA testing for early detection of subclinical AMR in living-donor transplants. This pilot study provides foundational evidence for dd-cfDNA-based surveillance strategies in Asian cohorts.