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.