Factors Other Than Rejection That Influence Dd-cfdna In Heart Transplant (ht) Recipients: A Real-world Experience

Introduction Donor-derived cell-free DNA (dd-cfDNA) is an established biomarker of rejection following HT. There is an unmet need to determine other factors that might influence dd-cfDNA. The association between dd-cfDNA and recipient age, gender, and time since transplant have not been well documented in HT. Herein we describe a retrospective review of the ProsperaTM Heart dd-cfDNA assay use in clinical practice and association with these variables. Methods We assessed all HT patients ≥18 yrs who underwent testing with the Prospera Heart assay as part of clinical care. Patients included for analysis had two or more tests within 90 days, and were <5 yrs post-HT. Results There were 90 unique pts transplanted between December 2017 and January 2022 contributing 256 commercial samples, analyzed for dd-cfDNA between September 2021 and March 2022 at our CLIA lab (Natera, San Carlos, CA). There were 66 male (197 tests) and 24 female (59 tests) pts. 30% of the total tests were found to be “high risk” (defined by having a dd-cfDNA fraction >0.15%), including 27% of tests among the male patients and 39% of tests among the female patients. There were no significant differences in dd-cfDNA fraction between male and female recipients, though a significant relationship between dd-cfDNA fraction and time since transplant was observed. A covariate analysis found that time since transplant was significant in predicting dd-cfDNA fraction (p<0.001). The results of a linear regression overlaid with the dd-cfDNA fraction data are shown in Figure 1A. We also observed significantly higher dd-cfDNA levels with increasing time since HT. A significantly higher mean of dd-cfDNA fraction was observed in the 35-54 year age range compared to older (p<0.001) and younger (p<0.01) recipients. However we did not observe a significant difference in dd-cfDNA fraction between the male and female recipients. Recipient dd-cfDNA fraction as a function of the recipient's age is shown in Figures 1B and 1C. Conclusions We found factors other than rejection influenced dd-cfDNA in HT pts, including time since transplant and age. We found no differences in levels between genders. The underlying mechanisms for these findings are unknown. Current clinical practice applies equal cutoffs for dd-cfDNA to screen for rejection in HT. Patient characteristics and other factors could be useful for more nuanced interpretation of dd-cfDNA results. Further studies are warranted to validate these findings in a larger cohort.