*Purpose: Donor derived-cell free DNA (dd-cfDNA) is a novel serum biomarker available for earlier prediction of acute rejection in renal allograft. Baseline dd-cfDNA values are <1% in 96% of kidney transplant recipients (KTRs). We aimed to explore any differences in baseline dd-cfDNA levels among deceased donor KTRs stratified by the mode of donor death: donation after brain death (DBD) vs. donation after cardiac death (DCD). We also aimed to stratify baseline dd-cfDNA values according to different levels of kidney donor profile index (KDPI).

*Methods: Our center has been checking dd-cfDNA levels (AlloSure, CareDx, Brisbane, CA) as for-cause and as surveillance in high immunological risk KTRs since 2018. We identified deceased donor KTRs at our center between April 2018 and June 2020 who had dd-cfDNA measured between 4 and 12 weeks post-transplant. A dd-cfDNA value ≥1.0% prompted allograft biopsy. Patient with biopsy evidence of rejection were excluded from the analysis since our aim was to compare baseline values. The average dd-cfDNA levels for each patient between 4 and 12 weeks post-transplant were compared between DBD and DCD KTRs and among the following KDPI groups: 0-20%, 21-50%, 51-84% and ≥85% using t test. A linear regression was constructed comparing dd-cfDNA levels with increasing KDPI.

*Results: We identified 80 deceased donor KTRs with 189 dd-cfDNAA levels during the study period. There was no significant difference between average values of dd-cfDNA levels between DBD (n=59) and DCD (n=21) KTRs (0.45±0.39 vs.0.47±0.26, p=0.84). The average dd-cfDNA levels stratified by KDPI categories were as follows: 0-20% (n=11): 0.30±0.15; 21-50% (n=21): 0.49±0.30; 51-84% (n=34): 0.38±0.23 and ≥85% (n=14): 0.72±0.61. There was significant linear correlation between dd-cfDNA levels and increasing KDPI as shown in figure 1.

*Conclusions:

Mode of donor death did not impact baseline dd-cfDNA levels despite increased risk for ischemia-reperfusion injury and delayed graft function with DCD kidney transplantation. Significant linear correlation between baseline dd-cfDNA levels and increasing KDPI could be reflective of higher levels of ongoing intra-graft inflammation with increasing KDPI. Our study indicates that baseline dd-cfDNA could be influenced by different donor characteristics that define KDPI.

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