Tacrolimus IPV Group Membership Does Not Consistently Track With Electronically Monitored or Self-reported Adherence in Adolescent and Young Adult Kidney Transplant Recipients.

Background: High intrapatient variability (IPV) of tacrolimus trough concentrations (SD ≥ 2, coefficient of variation (CV%) ≥ 30) is associated with rejection and graft loss and may indicate nonadherence. However, the association between tacrolimus IPV and electronically monitored or self-reported adherence is unknown.

Methods: This secondary analysis of the TAKE-IT (Teen Adherence in Kidney Transplant Effectiveness of Intervention Trial) compared electronically monitored and self-reported adherence between participants with high and low tacrolimus IPV among 103 adolescent and young adult kidney transplant recipients (mean age = 15.18 y, 59% male, 60% White, 65% >1-y posttransplant).

Results: Electronically monitored daily taking and timing adherence were not significantly associated with tacrolimus IPV group in binomial generalized linear mixed effects models: Participants with tacrolimus SD ≥ 2 or CV% ≥ 30 were no less likely to take each daily dose than those below these cutoffs (SD < versus ≥ 2: odds ratio [OR]; 0.84, 95% confidence interval [CI], 0.48-1.47;  = 0.54 and CV% < versus ≥ 30: OR, 0.72; 95% CI, 0.43-1.21;  = 0.22). Participants with tacrolimus SD ≥ 2 or CV% ≥ 30 were no less likely to take each daily dose on time than those below these cutoffs (SD < versus ≥ 2: OR, 0.70; 95% CI, 0.40-1.23;  = 0.21 and CV% < versus ≥ 30: OR, 0.68; 95% CI, 0.40-1.16;  = 0.15). Electronically monitored averages of doses taken, doses taken early/late, and differences from expected dose time were associated with tacrolimus IPV ( < 0.05) but were poor classifiers of IPV group membership (area under the curve < 0.70). Self-reported adherence was not associated with tacrolimus IPV.

Conclusions: Tacrolimus IPV group membership does not consistently track with behavioral adherence measures. Relying on tacrolimus IPV group membership may misidentify nonadherence in adolescent and young adult kidney transplant recipients.