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. 2025 Jul;29(7):987-994.
doi: 10.1007/s10157-025-02649-0. Epub 2025 Mar 17.

Pre-transplant tacrolimus fluctuations predict BK virus infection risk in kidney transplants

Hisashi Sakurai  1 , Teppei Okamoto  2 , Anna Yonemaya  1 , Fumiya Yonemaya  1 , Tomoko Hamaya  1 , Hirotake Kodama  1 , Naoki Fujita  1 , Hayato Yamamoto  1 , Kazuyuki Mori  1 , Takeshi Fujita  3 , Atushi Imai  1 , Reiichi Murakami  3 , Hirofumi Tomita  3 , Shingo Hatakeyama  1 , Chikara Ohyama  1
Affiliations

Pre-transplant tacrolimus fluctuations predict BK virus infection risk in kidney transplants

Hisashi Sakurai et al. Clin Exp Nephrol. 2025 Jul.

Abstract

Background: BK virus (BKV) infection is a significant complication in kidney transplant recipients, potentially leading to graft loss. The relationship between pre-transplant tacrolimus (TAC) pharmacokinetics and BKV infection risk remains unclear. This study aimed to investigate whether pre-transplant TAC blood concentration fluctuations are associated with BKV infection risk.

Methods: We conducted a retrospective study of 135 living donor kidney transplant recipients at Hirosaki University between 2006 and March 2024. Patients were divided into BKV-infected (BKV) and non-infected (non-BKV) groups. TAC blood concentrations were measured at 4 points, including 0 h (2 h before TAC administration), 4, 6, and 12 h on the day before transplantation. Changes in TAC concentration from baseline (0 h) were calculated for each time point. The concentration/dose (C0/D) ratio was used as an indicator of TAC metabolism rate.

Results: During a median follow-up of 54 months, 29 recipients developed BKV infection. The BKV group had significantly older donors and showed a significantly larger decrease in TAC concentration at 12 h compared to the non-BKV group (-1.5 vs. 0 ng/mL, P = 0.008). There was no significant difference in pre-transplant C0/D ratios between the two groups. A decrease of ≥ 1.5 ng/mL at 12 h was identified as a significant risk factor for BKV infection (hazard ratio: 2.44, 95% confidence interval: 1.11-5.32, P = 0.026) in a propensity score-based inverse probability of treatment weighting multivariate Cox proportional hazards analysis.

Conclusion: Pre-transplant TAC blood concentration fluctuations, particularly a large decrease at 12 h from baseline, may be associated with increased BKV infection risk.

Keywords: BK virus; Immunosuppression; Kidney transplantation; Pre-transplant pharmacokinetics; Tacrolimus.

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Conflict of interest statement

Declarations. Conflict of interest: The authors declare no conflicts of interest. Ethical approval: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional committee at Hirosaki University School of Medicine (IRB approval number 2019–099-1) and with the 1964 Helsinki declaration. Informed consent: Patient data were collected and analyzed to investigate the long-term prognosis. All data used in this study were anonymized and stripped of any personally identifiable information to ensure strict patient confidentiality in accordance with applicable regulations.

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