*PURPOSE: As next-generation biomarkers become more widespread, there is interest in understanding their prognostic utility. We examined the correlation between dd-cfDNA and eGFR among kidney transplant recipients with biopsy-proven ABMR at our center. *METHODS: Patients with biopsy-proven ABMR (Banff 2019) and dd-cfDNA results (AlloSure; CareDx, Inc.) within 1 month pre- to 1 week post-biopsy (without interval treatment) were included. Data on HLA, non HLA donor-specific antibodies (DSA) and eGFR were collected. Paired eGFR results at 3 time points (peak within 1 year pre-biopsy, at biopsy, and 6 months post-biopsy) were compared based on dd-cfDNA at the time of rejection (≥ 1.0% vs < 0.5%) and DSA/non-HLA status. *RESULTS: Of 30 patients included, 14 were HLA-DSA- (9 non-HLA+, 5 -), and 16 were HLA-DSA+ (3 non-HLA+, 1-, and 12 unknown). Median dd-cfDNA was 1.3% (IQR: 0.42 - 3.2). eGFR pre-biopsy, at biopsy, and at 6 months post-biopsy were 55.5mL/min (46 - 66), 44.5mL/min (33 - 58), and 44mL/min (31 - 59), respectively. When stratified by HLA-DSA and non-HLA Ab status, a decrease between pre- and peri-biopsy eGFR was nearly universal (except HLA-/non-HLA+ patients); at 6 months, median eGFR remained below pre-biopsy peaks in all groups, but the difference was statistically significant only in HLA-DSA+ patients (Fig 1). When stratified by dd-cfDNA levels, decreases in eGFR from pre-biopsy to peri-biopsy were also seen, however, while eGFR among high dd-cfDNA patients appeared to recover nearly to pre-biopsy levels (p = 0.05), eGFR among low dd-cfDNA patients remained moderately reduced (p = 0.03, Fig 2). *CONCLUSIONS: Though limited by small sample size and requiring validation in larger studies, our findings suggest that patients with lower dd-cfDNA at the time of ABMR may have a worse prognosis than those with higher dd-cfDNA. This finding is unexpected, but may be related to the degree of viable (and potentially rescuable) tissue affected by inflammatory injury as eGFR was lower (suggesting more extensive chronicity and scarring) at the time of biopsy in those with lower dd-cfDNA. Further interaction study between dd-cfDNA and eGFR at the time of biopsy with long term kidney function is warranted. [

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]CITATION INFORMATION: Dhaliwal T., Wadhwa A., Kitchel E., Shekhtman G., Datta N., Hui C., Bunnapradist S. Donor-Derived Cell-Free DNA (dd-cfDNA) Results and Clinical Outcomes in Antibody Mediated Rejection (ABMR) AJT, Volume 23, Issue 6, Supplement 1.

Tanveer Dhaliwal Undergraduate Student

UCLA

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