Size Doesn't Matter? Effect of Donor Volume on Donor-Derived Cell-Free DNA in Kidney Transplant Recipients: A Single-Center Perspective

Background: Donor-derived cell-free DNA (dd-cfDNA) has become an imperative noninvasive biomarker to identify subclinical allograft injury in kidney transplant recipients(KTRs). Multiple recipient factors including age, gender, pregnancy can influence dd-cfDNA levels. However the influence of donor factors are less known. We present our findings examining the impact of donor kidney volume on dd-cfDNA. Methods: A retrospective chart review was conducted for living donor kidney KTRs who underwent transplantation between 1/2020 and 10/2023. KTRs who had volume (KV) and dd-cfDNA (AlloSure, CareDx) data available were included in the study. Descriptive statistics were used for 4 cohorts based on kidney volume (mL): cohort 1:90-130, cohort 2: 131-160; cohort 3: 161-190; cohort 4:191-230. One-way analysis of variance (ANOVA) was performed to assess statistical significance in dd-cfDNA and eGFR in recipients at baseline and at 1 year between cohorts. Results: A total of 54 KTRs with KV and dd-cfDNA results met inclusion criteria. Median age at time of transplant for KTRs was 56.5 years with majority being white (66.7%) males (55.6%) with median BMI of 28.7. Median donor age was 41.5 years with BMI of 27.8. Majority donors were living related (61%) with 3 (5.5%) having hypertension. First dd-cfDNA was obtained at median of 34 days post-transplant with median being 0.18%. One-year dd-cfDNA was obtained at median of 355 days post-transplant with median being 0.18%. Similarly, eGFR at the time of 1st and 1-year dd-cfDNA was 50 and 58, respectively. When comparing dd-cfDNA and eGFR across 4 KV cohorts, there was no statistical significance noted. Conclusion: This cohort of 54 living donor KTRs demonstrates that KV may not have a significant impact on dd-cfDNA in adult patients. Additionally, there was no impact on 1 year graft function.