Predictive value of tacrolimus concentration/dose ratio in first post-transplant week for -polymorphism in kidney-transplant recipients.

BACKGROUND

Tacrolimus (TAC) is metabolized primarily by the -encoded enzyme family (, , and ). Individuals expressing the allele are considered fast metabolizers and generally require higher TAC doses to reach therapeutic levels.

AIM

To evaluate the predictive value of the TAC concentration-to-dose (C0/D) ratio for identifying polymorphisms in renal transplant recipients.

METHODS

Eighty-six kidney transplant recipients with TAC-based immunosuppression from the Department of Nephrology and Dialysis at Military Hospital 103 (Hanoi, Vietnam) were included in this retrospective study. Blood samples were collected within the first week post-transplantation to monitor TAC levels and to perform genotyping for genetic polymorphisms.

RESULTS

The genotype was identified in 37 patients (43%), in 40 patients (46.5%), and in 9 patients (10.5%). Patients carrying the or genotype, classified as fast metabolizers ( expressers), had significantly lower TAC C0 concentrations and C0/D ratios compared to slow metabolizers ( genotype) at multiple time points during follow-up (all < 0.001). Notably, the TAC C0/D ratio obtained on day 1 (0.91) was shown to predict polymorphism with a sensitivity of 84.6% and a specificity of 84.6%.

CONCLUSION

This study demonstrates that the TAC C0/D ratio provides a reliable predictive value for polymorphisms, which can be used to individualize TAC dosing in renal transplant recipients in Vietnam and other low-income countries.