Purpose: Donor-derived cell-free DNA (dd-cfDNA) discriminates active rejection in kidney transplant patients. Donor-specific antibodies (DSA) to HLA antigens are associated with risk of antibody-mediated rejection (ABMR). This study assessed the combined use of dd-cfDNA and DSA testing to diagnose ABMR. Methods: dd-cfDNA was assayed in 90 blood samples with paired DSA and clinically indicated biopsies from 87 kidney transplant patients. Sixteen cases met Banff criteria for active ABMR. Performance characteristics of dd-cfDNA for diagnosis of ABMR were determined for samples with prior or current positive DSA (DSA+, n=33). Results: The median level of dd-cfDNA (2.9%) in 16 samples from 16 DSA+ patients with a biopsy-confirmed ABMR was significantly higher than the median level (0.34%) in DSA+ patients without ABMR (p<0.001). The median level of dd-cfDNA in samples from DSA– patients was 0.29%. The sensitivity and specificity for detection of ABMR were 81% and 82%, respectively, for dd-cfDNA+/DSA+ samples. The positive predictive value (PPV) of dd-cfDNA+ to detect ABMR in DSA+ patients was 81%, whereas the NPV was 83%. The PPV for DSA+ alone was 48%. Conclusions: The combined use of dd-cfDNA and DSA testing may improve the non-invasive diagnosis of active ABMR in kidney transplant patients. Patients with dd-cfDNA+/ DSA+ results have a high probability of active ABMR.

CITATION INFORMATION: Jordan S., Bunnapradist S., Bromberg J., Langone A., Hiller D., Yee J., Sninsky J., Woodward R., Matas A. Donor-Derived Cell-Free DNA Identifies Antibody-Mediated Rejection with Graft Injury in DSA-Positive Kidney Transplant Recipients Am J Transplant. 2017;17 (suppl 3).

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