ASN's Mission

To create a world without kidney diseases, the ASN Alliance for Kidney Health elevates care by educating and informing, driving breakthroughs and innovation, and advocating for policies that create transformative changes in kidney medicine throughout the world.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005


The Latest on Twitter

Kidney Week

Abstract: SA-PO512

Median Intrapatient Tacrolimus Variability Is Comparable between Renal Transplant Centres: A Multicentre UK Retrospective Study

Session Information

Category: Transplantation

  • 1702 Transplantation: Clinical and Translational


  • Bottomley, Matthew James, Churchill Hospital, Oxford, United Kingdom

Group or Team Name

  • UK Transplant Audit Collaborative

Tacrolimus is an immunosuppressant with a narrow therapeutic window and regular serum trough level monitoring is necessary. Increased intrapatient variability (IPV) in these levels has been identified as a risk factor for graft rejection and loss after renal transplant. Previous reports have been from single centre studies with varying methodologies: thus it is unclear how comparable tacrolimus levels and hence IPV are between centres and studies.


A retrospective study was undertaken in five UK transplant centres using a unified methodology. Renal databases in all centres were interrogated to provide demographic details and laboratory results for all renal transplant recipients (RTR) between 1 January 2009 and 31 December 2014 who received tacrolimus therapy. RTR were excluded if they received dual-organ transplants or if death or graft loss occurred within two years of transplantation, or if their immunosuppression regimens included modified release tacrolimus. IPV was calculated from trough levels taken during the 6-12 month post-transplant period (T1) and the last 12 months of follow-up (T2).


A total of 1070 eligible RTR across the five centres were included (Table 1). Despite variation in ethnic make-up and median age across centres, median tacrolimus IPV at both T1 and T2 was similar at around 14-16%. Across all centres male gender and non-Caucasian ethnicity were not associated with increased IPV. Increasing age did not correlate with IPV. There was no correlation between duration of transplant follow-up and T2 IPV.


In the first national retrospective study of this kind, we report that despite variation in population demographics between centres, median tacrolimus IPV is remarkably consistent. Increased IPV does not appear to be associated with age or ethnicity. This data will be pooled to enable formulation of a 'national standard' IPV, which will allow further study to assess whether RTR with an above median IPV have poorer transplant outcomes.

Table 1: Tacrolimus IPV in UK Transplant Centres
 Oxford (n=284)King's London (n=134)Liverpool (n=171)Glasgow (n=168)Manchester (n=313)
% Male60.6%76.1%61.4%63.8%63.9%
Median (IQR) age at transplant53 (42 - 61)51 (40 - 59)51 (39 - 60)50 (39 - 56)46 (37 - 57)
Median (IQR) T1 Tacrolimus IPV15.4% (10.4 - 22.1)14.8% (10.1 - 20.4)16.4% (12.2 - 23.0)15.6% (12.3 - 23.2)15.9% (11.8 - 22.3)
Median (IQR) T2 Tacrolimus IPV16.0% (10.3 - 24.0)14.8% (9.8 - 23.9)14.9% (8.9 - 21.1)14.0% (9.4 - 19.5)14.9% (10.6 - 23.7)


  • Commercial Support