*PURPOSE: Donor-derived cell-free DNA (dd-cfDNA) is an established biomarker for surveillance following kidney transplantation. To date many of the published studies have focused on short to medium term surveillance and there remains a paucity of data describing dd-cfDNA distributions in kidney transplant recipients (KTR) >2 years post-transplant. This study describes dd-cfDNA trends in KTR stratified by time post-transplant with a focus on cohorts >2 years following transplantation. *METHODS: This is a single center retrospective cohort study of dd-cfDNA test results (AlloSure, CareDx®) collected from KTR at the University of Maryland from 1/1/2017 - 11/17/2022. Dd-cfDNA testing was for both surveillance and for-cause indications. A linear mixed model was used to test the association of dd-cfDNA levels over time. P values were calculated for comparison of groups across time post-transplant with T-test using Satterthwaite’s method. *RESULTS: There was a total of 5,955 dd-cfDNA results from 1,186 unique KTR with a median of 0.20% (IQR 0.14%, 0.35%) (Table 1). Linear mixed models demonstrated that mean dd-cfDNA levels gradually decreased over time by year post-transplant (p=0.004), however this was not statistically significant when comparing each time group (Figure 1A). The distribution of dd-cfDNA scores was consistent across the 4 time periods post-transplant (2 years post-transplant. Of these 800 patients, 23.1% had at least one elevated dd-cfDNA level >0.5% (Figure 2). [

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] *CONCLUSIONS: We observed similar distributions in dd-cfDNA results duringCITATION INFORMATION: Weir M., Yau J., Ibrahim M., Haririan A., Bromberg J. Evaluation of Dd-Cfdna Measures in Kidney Transplant Recipients More Than Two Years Post-Transplantation AJT, Volume 23, Issue 6, Supplement 1.

Matthew Weir MD

University of Maryland

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