Donor-Derived Cell-Free DNA for Diagnosing Subclinical Rejection: A Pilot Multicenter Study in Japanese Living-Donor...

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.

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.

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.

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.