Introduction

Nonadherence to immunosuppressive medication post renal transplant is an importnat risk factor for rejection and graft loss. In this study we assess the association between intrapatient variability of tacrolimus levels and the patient's rate of outpatient clinic non-attendance and the impact on renal allograft outcomes.

Method

We retrospectively analysed 668 patients who received a kidney only transplant between 01/11/2005 and 01/09/2013. All patients received alemtuzumab induction and tacrolimus monotherapy with a steroid sparing protocol with a target pre-trough tacrolimus level of 5-8ng/ml. Coefficient of variance (COV) was defined as standard deviation/mean of all outpatient tacrolimus trough levels taken between 6 and 12 months post-transplant. High variability (HV) was defined as a COV > median of the overall cohort and low variability (LV) was defined as a COV ≤ median of the overall cohort.

Results

5983 tacrolimus levels were included in the analysis. The mean number of samples analysed per patient was 8.96 ± 3.78 (range 2-23). The median COV of tacrolimus levels was 18.15%. Patients with a HV of tacrolimus levels were significantly more likely not to attend their outpatient appointments; the median number of non-attendances was 4 (range 0-22) in the HV group and 2 (range 0-17) in the LV group (p<0.0001). Patients who developed rejection, a DSA or lost their graft had a significantly higher number of outpatient non-attendances than those patients who did not develop rejection, a DSA or lose their graft.

Conclusion

This study shows that patients with a HV of tacrolimus levels are more likely not to attend outpatient clinic appointments and a high nonattendance rate is associated with a significantly increased risk of development of DSA, rejection and graft loss. This analysis supports the need for a prospective study to assess strategies which minimise nonadherence and reduce the risk of development of rejection and graft loss.

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