High Intrapatient Tacrolimus Variability and Increased Cell-Free DNA in Kidney Transplant Recipients.

Introduction: An inverse relationship has been identified between tacrolimus serum concentrations and donor-derived cell-free DNA (dd-cfDNA) levels after lung transplant, but limited data exists on this relationship in the kidney transplant population. Project Aim: The purpose of this evaluation was to examine the relationship between high tacrolimus variability and elevated dd-cfDNA levels in kidney and simultaneous pancreas-kidney transplant recipients at a single center. Design: Single-center, retrospective, descriptive comparative evaluation of kidney and pancreas-kidney transplant recipients who received longitudinal ddcfDNA surveillance. Intrapatient tacrolimus variability was assessed using the coefficient of variation (%CV) measured between 1 and 12 months posttransplant. Pediatrics, retransplant or multiorgan transplant recipients, and pregnant recipients were excluded. Results: One hundred fifteen recipients with 518 dd-cfDNA levels and 3028 tacrolimus troughs were assessed. Pancreas-kidney recipients had significantly higher median dd-cfDNA (0.29% vs. 0.18%, P = .034) and were excluded from analysis. Ninety-nine kidney transplant recipients were included for analysis. Recipients with tacrolimus %CV ≥30 (N = 66) had significantly higher median dd-cfDNA than %CV <30 (0.22% vs. 0.17%, P = .031). Tacrolimus %CV ≥30 demonstrated higher median peak dd-cfDNA than %CV <30, though this was not statistically significant (0.36% vs. 0.28%, P = .058). Conclusion: These data demonstrated that high intrapatient tacrolimus variability may be associated with elevated dd-cfDNA in the first year after kidney transplant.

Nuances in the interpretation and utility of donor-derived cell-free DNA in lung transplantation following allogeneic hematopoietic stem cell transplantation - Case report.

Respiratory complications following allogeneic HSCT can lead to severe morbidity and mortality. Lung transplantation (LT) is a potential treatment for select patients with late-onset non-infectious pulmonary complications post-HSCT. Donor-derived cell-free DNA (dd-cfDNA) is a noninvasive biomarker for monitoring the health of allografts following LT. However, its utility in a multi-genome setting of LT after HSCT has not yet been clinically validated. Here we describe a case of a 75-year-old, male patient who underwent single-lung transplantation for BOS related to chronic GVHD and presented with persistently elevated dd-cfDNA levels. In a surveillance biopsy, the patient was diagnosed with mild acute cellular rejection at three months. The patient's lung function remained stable, and the reported dd-cfDNA levels decreased after the rejection episode but remained elevated above levels that would be considered quiescent for LT alone. In this unique setting, as 3 different genomes contributed to the dd-cfDNA% reported value, valuable insight was obtained by performing further analysis to separate the specific SNPs to identify the contribution of recipient, lung-donor, and HSCT-donor cfDNA. This study highlights the potential utility of dd-cfDNA in the multi-genome setting of lung transplant post-HSCT, nuances that need to be considered while interpreting the results, and its value in monitoring lung rejection.