Sex-Specific Patterns of Donor-Derived Cell-Free DNA in Heart Transplant Rejection: An Analysis from the Genomic Research Alliance for Transplantation (GRAfT)

Introduction Non-invasive methods for surveillance of acute rejection are increasingly used in heart transplantation (HT), including donor-derived cell-free DNA (dd-cfDNA). As other cardiac biomarkers differ by sex, we hypothesized that there may be sex-specific differences in performance of dd-cfDNA for detection of acute rejection. The purpose of the current study was to examine patterns of dd-cfDNA seen in quiescence and acute rejection in males and female transplant recipients. Methods Patients enrolled in the Genomic Research Alliance for Transplantation (GRAfT) who were ≥18 years at the time of HT were included. Rejection was defined by endomyocardial biopsy with ISHLT acute cellular rejection (ACR) grade ≥2R and/or antibody-mediated rejection ≥ pAMR 1. dd-cfDNA was quantitated using shotgun sequencing. Median dd-cfDNA levels were compared between sexes during quiescence and rejection. The performance of dd-cfDNA by sex was assessed using AUROC. Allograft injury was defined as ddcfDNA ≥0.25%. Results 151 unique patients (49 female, 32%) were included in the analysis with 1119 available dd-cfDNA measurements. Baseline characteristics including demographics and comorbidities were not significantly different between sexes. During quiescence, there were no significant sex differences in median dd-cfDNA level (0.04% [IQR 0.00, 0.16] in females vs 0.03% [IQR 0.00, 0.12] in males, p = 0.22). There were no significant sex differences in median dd-cfDNA for ACR (0.33% [0.21, 0.36] in females vs 0.32% [0.21, 1.10] in males, p = 0.57). Overall, median dd-cfDNA levels were higher in AMR than ACR but did not significantly differ by sex (0.50% [IQR 0.18, 0.82] in females vs 0.63% [IQR 0.32, 1.95] in males, p = 0.51). Elevated dd-cfDNA detected ACR/AMR with an AUROC of 0.83 in females and 0.89 in males, p-value for comparison = 0.16. Discussion There were no significant sex differences in dd-cfDNA levels during quiescence and rejection. Performance characteristics were similar, suggesting that similar diagnostic thresholds can be used in men and women for rejection surveillance.