Background: Tacrolimus (TAC) is the mainstay of immunosuppression for kidney transplantation (KT). Although TAC has a narrow therapeutic index, appropriate trough concentrations of TAC have not been clearly defined to date.

Method: We analyzed patients underwent KT between 2011 and 2015 and treated with TAC-based triple immunosuppressant. Mean trough concentration and intrapatient variability (IPV) were calculated from the TAC concentrations between 6 and 12 months after KT. Patients were grouped according to mean TAC concentration (high TAC [≥5 ng/mL] vs. low TAC [<5 ng/mL]) and IPV (high IPV [upper tertile] vs. low IPV [lower two tertiles]).

Results: A total of 347 patients with a mean TAC concentration of 5.7 ± 2.0 ng/mL were included (143 low TAC and 204 high TAC groups). Mean TAC concentration was not different between high IPV and low IPV groups (5.8 ± 1.8 vs. 5.6 ± 2.3 ng/mL, P=0.39). The composite end point consisting of graft loss and allograft rejection 1 year after transplant was associated with high IPV rather than mean TAC concentration. After adjustment for delayed graft function, diabetes, and age, high IPV remained a significant risk factor for the composite end point (hazard ratio: 2.06, 95% CI: 1.08-3.94, P<0.028). High IPV group had significantly worse glomerular filtrate rate at 1, 2, and 3 years post-transplant.

Conclusion: This suggests that high IPV rather than mean concentration is related to worse outcomes in KT.

CITATION INFORMATION: Lee J., Lee J., Jung Y., Kim D., Song S., Lee J., Lee J., Kim M., Kim S., Kim Y., Kim B., Huh K. The Effect of Tacrolimus Trough Level and Intrapatient Variability on the Transplant Outcomes in Kidney Transplantation Am J Transplant. 2017;17 (suppl 3).

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