Variability in tacrolimus blood levels increases the risk of late rejection and graft loss after solid organ transplantation in older children

Implementation of a multicomponent medication adherence promotion system is associated with a decrease in late T-cell-mediated rejection

Poor immunosuppression adherence in pediatric recipients of liver transplant (LT) contributes to late T-cell-mediated rejection (TCMR) in ~90% of cases and increases the risk of mortality. A medication adherence promotion system (MAPS) was found to reduce late rejection in pediatric recipients of kidney transplants. Using quality improvement methodology, we adapted and implemented the MAPS in our LT clinic. Our primary outcome was population-level rates of late TCMR, measured as a monthly incident rate. Three-hundred fourteen patients undergoing LT are currently cared for at our institution. One-hundred sixty-two (52%) are females with a median age of 16 years and a median age at LT of 2 years. Preimplementation, monthly rejection rates were 0.84 rejections per 100 patient-months. After iterative implementation of MAPS over 2.3 years, monthly rejection rates decreased to 0.46 rejections per 100 patient-months, a 45% decrease in late TCMR. Implementation of MAPS was associated with a sustained 45% decrease in TCMR at a single center, suggesting that quality improvement tools may help improve clinical outcomes. MAPS may be an important tool to ensure long-term allograft health. Future studies should rigorously test MAPS across a multicenter sample.

Factors influencing intrapatient variability of tacrolimus and its association with 1-year post-transplant outcomes in pediatric liver transplant recipients

Objective

This study aims to explore the factors influencing tacrolimus intrapatient variability (TAC-IPV) and its association with 1-year post-transplant outcomes in pediatric liver transplant recipients.

Methods

Clinical and biological data of pediatric patients after liver transplantation were collected. The patients were divided into high- and low-IPV groups according to the median TAC-IPV for statistical comparisons. Factors with p < 0.05 in univariate analysis were introduced into binomial logistic regression analysis. Correlation analysis was used to test the connections between the Tac-IPV and outcomes within 1 year after liver transplantation (LT), and Kaplan-Meier was used to draw the survival curves.

Results

A total of 116 children underwent 746 measurements of TAC trough concentrations. The median TAC-IPV was 32.31% (20.81%, 46.77%). Hematocrit (p = 0.017) and concomitant medications (p = 0.001) were identified as independent influencing factors for TAC-IPV. The incidence of transplant rejection (p = 0.008), CMV infection (p < 0.001), and hospital admission due to infection (p = 0.003) were significantly higher in the high-IPV group than in the low-IPV group. Kaplan-Meier survival analysis suggests that after considering the time factor, high IPV (IPV > 32.31%) was still significantly associated with transplant rejection (HR = 3.17 and p = 0.005) and CMV infection (HR = 2.3 and p < 0.001) within 1 year after LT.

Conclusion

The study highlights the significant variation in TAC-IPV among children post-liver transplantation, emphasizing the impact of hematocrit levels and concomitant medications on TAC-IPV. Elevated TAC-IPV is associated with increased risks of transplant rejection, CMV infection, and readmission due to infection in the first year after liver transplantation. Close monitoring of patients with high TAC-IPV is recommended to promptly detect adverse reactions and provide timely intervention and treatment.

Nonadherence to Immunosuppressant Therapy of Kidney Transplant Candidate Patients: External Validation of the KATITA-25 Scale

BACKGROUND

The self-administered Kidney AlloTransplant Immunosuppressive Therapy Adherence (KATITA-25) questionnaire is a multidimensional scale for use in the pretransplant setting that evaluates the predisposition to nonadherence of patients who are candidates to kidney transplant. The scale has shown adequate internal consistency and test-retest reliability. This study presents the results of an external validation study of the KATITA-25 scale.

METHODS

Patients >18 y old scheduled for kidney transplant were included in this multicenter study. The KATITA-25 scale was administered before surgery and then at 3-mo posttransplantation for evaluation of scale sensitivity to change. At this time, 2 validated medication adherence scales were applied for assessment of concurrent validity. For evaluation of predictive validity, nonadherence to immunosuppressive medication was assessed at 6 and 12 mo after transplantation by 3 independent methods: patient self-report of nonadherence using the Morisky-Green-Levine Medication Assessment Questionnaire scale, serum trough levels of immunosuppressants, and pharmacy refills.

RESULTS

Three twenty-two patients were available for evaluation of concurrent validity and 311 patients of predictive validity. After kidney transplant, the median KATITA-25 score decreased from 20 to 8 ( P  < 0.001), demonstrating scale sensitivity to change, and the KATITA-25 score showed correlation with the Basel Assessment of Adherence to Immunosuppressive Medication Scale score (Spearman's ρ 0.18, P  = 0.002) and the Cuestionario para la Evaluación de la Adhesión al Tratamiento Antiretroviral scores (ρ -0.17, P  = 0.002), confirming concurrent validity. The nonadherence rate was 57.6%. The scale predictive validity was demonstrated by the area under the receiver operating characteristics curve (0.68), sensitivity (59.8%), specificity (68.2%), and positive predictive value (71.8%).

CONCLUSIONS

This external validation study of KATITA-25 scale provided evidence of sensitivity to change, and structural, criterion, and predictive validity.

Influence of Tacrolimus Intrapatient Variability on Allograft Rejection Frequency and Survival Following Liver Transplantation

BACKGROUND

Tacrolimus is the primary calcineurin inhibitor used in immunosuppressive regimens to prevent allograft rejection (AR) after organ transplantation. Recent studies have linked intrapatient variability (IPV) of tacrolimus with AR occurrence and reduced survival, especially in kidney transplant recipients. However, limited data are available on the impact of tacrolimus IPV on adverse outcomes after liver transplantation (LT).

AIMS

The aim of this study was to assess the association between tacrolimus IPV using various methodologies with acute AR and long-term patient survival after LT.

METHODS

All patients who underwent LT from January 2010 to July 2021 were retrospectively evaluated. Tacrolimus IPV was calculated for each patient using the mean and SD, mean absolute deviation (MAD), coefficient of variation (CV), and time in therapeutic range (TTR). These measures were then compared with AR within the first 24 months after LT and to long-term survival.

RESULTS

Out of 234 patients, 32 (13.7%) developed AR and 183 (78.2%) survived, with a mean follow-up of 101 ± 43 months. Tacrolimus IPV, assessed by mean, SD, MAD, and CV, was 8.3 ± 2.1, 2.7 ± 1.3, 32.0% ± 11.7%, and 39.4% ± 15.4%, respectively. There was no statistically significant correlation between Tacrolimus IPV and AR or survival post-LT.

CONCLUSIONS

In a large cohort of patients from diverse racial backgrounds, tacrolimus IPV was not associated with clinically relevant outcomes such as AR and survival after LT.

Tacrolimus intra-patient variability measures and its associations with allograft clinical outcomes in kidney transplantation

AIMS

Tacrolimus (Tac) is commonly prescribed in solid organ transplantation to prevent immune-mediated damage to the graft. However, its pharmacokinetics show substantial variability between and within patients. Intra-patient variability of tacrolimus (Tac-IPV) has emerged as a novel marker to predict transplant outcomes. Numerous studies report varying associations between Tac-IPV and clinical outcomes, with Tac-IPV measures showing wide discrepancies among these studies. This inconsistency could be a significant factor that influences the various outcomes reported in different studies. Our review comprehensively assesses the relationship between various Tac-IPV measures and their associations with clinical outcomes in transplant patients.

METHODS

A comprehensive literature search was conducted using the PubMed and Embase databases, covering the period from 2004 to March 31, 2023. The search focused on studies that examined the relationship between Tac-IPV and clinical outcomes in kidney transplantation (KT). The inclusion criteria were specific to studies addressing Tac-IPV, including measures such as standard deviation (SD), coefficient of variation (CV), time-weighted coefficient of variability (CV), mean absolute deviation (MAD), and Tac variability score (TVS). Clinical outcomes included the development of de novo donor-specific antibodies (dnDSA), rejection episodes, graft loss, and graft failure.

RESULTS

Among the 33 studies that met the inclusion criteria, a notable proportion presented conflicting findings in their assessment of various Tac-IPV measures regarding dnDSA, rejection episodes, graft loss, and graft failure.

CONCLUSIONS

Most studies have identified a correlation between high Tac-IPV and poor clinical outcomes; however, this relationship is multifactorial. Influencing factors include the metabolic status of KT patients, the timing of Tac-IPV calculations, and the criteria for defining high and low Tac-IPV thresholds, including the size and selection method. CV, MAD, and TWCV are the metrics that are most frequently used to determine Tac-IPV. Additionally, most of the methods for establishing Tac-IPV thresholds typically employ receiver operating characteristic (ROC) curves and median values. It is also notable that studies examining the clinical significance of Tac-IPV often include tacrolimus levels measured six months after kidney transplantation.

Non-invasive biomarkers of acute rejection in pediatric kidney transplantation: New targets and strategies

Kidney transplantation is the preferred treatment for pediatric end-stage renal disease. However, pediatric recipients face unique challenges due to their prolonged need for kidney function to accommodate growth and development. The continual changes in the immune microenvironment during childhood development and the heightened risk of complications from long-term use of immunosuppressive drugs. The overwhelming majority of children may require more than one kidney transplant in their lifetime. Acute rejection (AR) stands as the primary cause of kidney transplant failure in children. While pathologic biopsy remains the "gold standard" for diagnosing renal rejection, its invasive nature raises concerns regarding potential functional impairment and the psychological impact on children due to repeated procedures. In this review, we outline the current research status of novel biomarkers associated with AR in urine and blood after pediatric kidney transplantation. These biomarkers exhibit superior diagnostic and prognostic performance compared to conventional ones, with the added advantages of being less invasive and highly reproducible for long-term graft monitoring. We also integrate the limitations of these novel biomarkers and propose a refined monitoring model to optimize the management of AR in pediatric kidney transplantation.

High intra-patient variability of tacrolimus within post-operative 1 month predicted worse 1-year outcomes in pediatric liver transplant recipients

BACKGROUND

The pharmacokinetics of tacrolimus (TAC) show high intra-patient variability (IPV), which is associated with poor long-term outcomes following adult liver transplantation (LT). However, this relationship remains to be confirmed in pediatric liver transplant (PLT) recipients. The present study aimed to investigate the association between TAC IPV and grafts or patient outcomes after pediatric liver transplantion.

METHODS

This retrospective study included 848 PLT recipients (including infants) between January, 2016, and June, 2021. The IPV of TAC concentrations was estimated by calculating the coefficient of variation (CV) of trough concentrations in whole blood within 1 month after transplantation. Patients were categorized into two groups, low IPV (CV < 45%) and high IPV (CV ≥ 45%), based on the third quartile of the CV distribution.

RESULTS

A total of 848 patients were included in our study. The low CV group included 614 patients, with a mean TAC trough concentration of 8.59 ± 1.65 ng/ml and a median CV of 32.37%. In contrast, the high CV group included 214 patients, the mean TAC trough concentration and median CV were 8.81 ± 2.00 ng/ml and 54.88%, respectively. The median hospital duration was significantly higher in the high CV group (22 days vs. 20 days, P = 0.01). Univariate analysis was performed to evaluate the significant differences in 1-year recipient survival (P = 0.041) and 1-year graft survival (P = 0.005) between the high- and low-CV groups. Moreover, high CV (HR 2.316, 95%CI 1.026-5.231, P = 0.043) and persistent EBV viremia (HR 13.165, 95%CI 3.090-56.081, P < 0.001) were identified as independent risk factors for 1- year mortality after PLT.

CONCLUSIONS

PLT recipients with high TAC trough concentration of CV in the first month were associated with poor 1-year outcomes. This CV calculation provides a valuable strategy to monitor TAC exposure.

Medication adherence in pediatric kidney transplantation: How to build a bridge over troubled water

Adhering to the immunosuppressive regimen remains one of the biggest challenges for children and adolescents after kidney transplantation. The first paper on nonadherence, co-authored by Dr. Fine, appeared in Pubmed over 45 years ago. Since then, many clinicians and researchers tried to better understand nonadherence and are looking for effective ways to support young people in implementing the complex medication regimen in their daily lives. As a tribute to Dr. Fine, we conducted a comprehensive review providing an overview of adherence-enhancing interventions in the field of pediatric kidney transplantation, thereby focusing on strategies that not only are effective but can also be embedded in daily clinical practice successfully and sustainably. This overview is preceded by a discussion about how to find out who is in need of supportive interventions. We will also argue that interventions should already start before pediatric kidney transplantation and discuss how to decide whether or not a young patient with nonadherence-induced graft loss should undergo retransplantation. We hope this comprehensive overview will rekindle the hope that we can finally turn the tide and beat one of pediatric kidney transplantation's main enemies.

Safety and Efficacy of Conversion to Once-Daily Tacrolimus from Twice-Daily Tacrolimus in Pediatric Liver Transplant Recipients

BACKGROUND

Nonadherence to immunosuppression is the most common cause of late acute rejection in pediatric liver transplant (LT) recipients. A prolonged-release once-daily tacrolimus formulation was developed to improve adherence and long-term allograft survival.

METHODS

We screened 179 pediatric LT recipients who converted from twice-daily tacrolimus (TD-TAC) to once-daily tacrolimus (OD-TAC) between February 2011 and September 2019.

RESULTS

One hundred seventy-nine recipients converted to OD-TAC and were followed for 18 months. 152 OD-TAC-converted recipients (84.9%) experienced uneventful follow-up, while 21 recipients showed LFT elevation. Four recipients had biopsy-proven acute rejection within six months of conversion, all of which were successfully treated with steroid pulse. 166 recipients (92.7%) remain on OD-TAC and 13 (7.3%) were switched back to TD-TAC. The mean tacrolimus trough level significantly decreased three months following conversion (3.14 ± 1.9 ng/mL) compared with pre-conversion levels (3.69 ± 1.98 ng/mL). Mean tacrolimus trough levels remained unchanged from 3 months to 12 months following conversion. Percent coefficient of variation of tacrolimus trough levels decreased significantly from 32.5 ± 16.4 ng/mL to 27.5 ± 15.6 ng/mL after conversion to OD-TAC, reflecting a decrease in variation of tacrolimus trough levels following conversion.

CONCLUSIONS

Conversion to OD-TAC in pediatric LT recipients with stable graft function is safe and effective.

LEVEL OF EVIDENCE

Level IV.

The improving Medication Adherence in Adolescents and young adults following Liver Transplantation (iMALT) multisite trial: Design and trial implementation considerations

BACKGROUND/AIMS

Medication non-adherence is a leading cause of transplant rejection, organ loss, and death; yet no rigorous controlled study to date has shown compelling clinical benefits from an adherence-improving intervention. Non-adherent patients are less likely to participate in trials, and therefore, most studies enroll a majority of adherent patients who do not stand to benefit from the intervention, as they do not have the condition (non-adherence) under investigation. The improving Medication Adherence in adolescent Liver Transplant recipients trial specifically targets non-adherent patients to investigate whether a remote intervention to improve adherence results in reduced incidence of biopsy-confirmed rejection.

METHODS

Improving Medication Adherence in adolescent Liver Transplant is a randomized single-blind controlled multisite, multinational National Institutes of Health-funded trial involving 13 pediatric transplant centers in the United States and Canada. An innovative, objective adherence biomarker-the Medication Level Variability Index, which is the standard deviation of a series of medication blood levels for each patient, is used to identify non-adherent patients at risk for rejection. The index is computed using electronic health record information for all potentially eligible patients based on repeated reviews of the entire clinic's roster. Identified patients, after consent, are randomized to intervention versus control (treatment as usual) arms. The remote intervention is delivered for 2 years by trained interventionists who reside in various locations in the United States. The primary outcome is the incidence of biopsy-confirmed acute cellular rejection, as confirmed by a majority vote of three pathologists who are masked to the study allocation and clinical information.

DISCUSSION

Improving Medication Adherence in adolescent Liver Transplant includes several innovative design elements. The use of a validated, objective adherence index to survey a large cohort of transplant recipients allows the teams to avoid bias inherent in both convenience sampling and referral-based recruitment and enroll only patients whose computed index indicates substantially increased risk of rejection. The remote intervention paradigm helps to engage patients who are by definition hard to engage. The use of an objective, masked medical (rather than behavioral) outcome measure reduces the likelihood of biases related to clinical information and ensures broad acceptance by the field. Finally, monitoring for potential adverse events related to increased medication exposure due to the adherence intervention acknowledges that a successful intervention (increasing adherence) could have detrimental side effects via increased exposure to and potential toxicity of the medication. Such monitoring is almost never attempted in clinical trials evaluating adherence interventions.

Impact of tacrolimus intra-patient variability in adverse outcomes after organ transplantation

Tacrolimus (Tac) is currently the most common calcineurin-inhibitor employed in solid organ transplantation. High intra-patient variability (IPV) of Tac (Tac IPV) has been associated with an increased risk of immune-mediated rejection and poor outcomes after kidney transplantation. Few data are available concerning the impact of high Tac IPV in non-kidney transplants. However, even in kidney transplantation, there is still a controversy whether high Tac IPV is indeed detrimental in respect to graft and/or patient survival. This may be due to different methods employed to evaluate IPV and distinct time frames adopted to assess graft and patient survival in those reports published up to now in the literature. Little is also known about the influence of high Tac IPV in the development of other untoward adverse events, update of the current knowledge regarding the impact of Tac IPV in different outcomes following kidney, liver, heart, lung, and pancreas tran splantation to better evaluate its use in clinical practice.

Rejection markers in kidney transplantation: do new technologies help children?

Recent insights in allorecognition and graft rejection mechanisms revealed a more complex picture than originally considered, involving multiple pathways of both adaptive and innate immune response, supplied by efficient inflammatory synergies. Current pillars of transplant monitoring are serum creatinine, proteinuria, and drug blood levels, which are considered as traditional markers, due to consolidated experience, low cost, and widespread availability. The most diffuse immunological biomarkers are donor-specific antibodies, which are included in routine post-transplant monitoring in many centers, although with some reproducibility issues and interpretation difficulties. Confirmed abnormalities in these traditional biomarkers raise the suspicion for rejection and guide the indication for graft biopsy, which is still considered the gold standard for rejection monitoring. Rapidly evolving new "omic" technologies have led to the identification of several novel biomarkers, which may change the landscape of transplant monitoring should their potential be confirmed. Among them, urinary chemokines and measurement of cell-free DNA of donor origin are perhaps the most promising. However, at the moment, these approaches remain highly expensive and cost-prohibitive in most settings, with limited clinical applicability; approachable costs upon technology investments would speed their integration. In addition, transcriptomics, metabolomics, proteomics, and the study of blood and urinary extracellular vesicles have the potential for early identification of subclinical rejection with high sensitivity and specificity, good reproducibility, and for gaining predictive value in an affordable cost setting. In the near future, information derived from these new biomarkers is expected to integrate traditional tools in routine use, allowing identification of rejection prior to clinical manifestations and timely therapeutic intervention. This review will discuss traditional, novel, and invasive and non-invasive biomarkers, underlining their strengths, limitations, and present or future applications in children.

Contemporary Biomarkers for Renal Transplantation: A Narrative Overview

Renal transplantation (RT) is the preferred treatment for end-stage renal disease. However, clinical challenges persist, i.e., early detection of graft dysfunction, timely identification of rejection episodes, personalization of immunosuppressive therapy, and prediction of long-term graft survival. Biomarkers have emerged as valuable tools to address these challenges and revolutionize RT patient care. Our review synthesizes the existing scientific literature to highlight promising biomarkers, their biological characteristics, and their potential roles in enhancing clinical decision-making and patient outcomes. Emerging non-invasive biomarkers seemingly provide valuable insights into the immunopathology of nephron injury and allograft rejection. Moreover, we analyzed biomarkers with intra-nephron specificities, i.e., glomerular vs. tubular (proximal vs. distal), which can localize an injury in different nephron areas. Additionally, this paper provides a comprehensive analysis of the potential clinical applications of biomarkers in the prediction, detection, differential diagnosis and assessment of post-RT non-surgical allograft complications. Lastly, we focus on the pursuit of immune tolerance biomarkers, which aims to reclassify transplant recipients based on immune risk thresholds, guide personalized immunosuppression strategies, and ultimately identify patients for whom immunosuppression may safely be reduced. Further research, validation, standardization, and prospective studies are necessary to fully harness the clinical utility of RT biomarkers and guide the development of targeted therapies.

Psychosocial Diagnosis and Treatment Before and After Organ Transplantation

BACKGROUND

This new clinical practice guideline concerns the psychosocial diagnosis and treatment of patients before and after organ transplantation. Its objective is to establish standards and to issue evidence-based recommendations that will help to optimize decision making in psychosocial diagnosis and treatment.

METHODS

For each key question, the literature was systematically searched in at least two databases (Medline, Ovid, Cochrane Library, and CENTRAL). The end date of each search was between August 2018 and November 2019, depending on the question. The literature search was also updated to capture recent publications, by using a selective approach.

RESULTS

Lack of adherence to immunosuppressant drugs can be expected in 25-30% of patients and increases the odds of organ loss after kidney transplantation (odds ratio 7.1). Psychosocial interventions can significantly improve adherence. Metaanalyses have shown that adherence was achieved 10-20% more frequently in the intervention group than in the control group. 13-40% of patients suffer from depression after transplantation; mortality in this group is 65% higher. The guideline group therefore recommends that experts in psychosomatic medicine, psychiatry, and psychology (mental health professionals) should be involved in patient care throughout the transplantation process.

CONCLUSION

The care of patients before and after organ transplantation should be multidisciplinary. Nonadherence rates and comorbid mental disorders are common and associated with poorer outcomes after transplantation. Interventions to improve adherence are effective, although the pertinent studies display marked heterogeneity and a high risk of bias.

Personalized Tacrolimus Dosing After Liver Transplantation: A Randomized Clinical Trial

Background

Inter- and intra-individual variability in tacrolimus dose requirements mandates empirical clinician-titrated dosing that frequently results in deviation from a narrow target range. Improved methods to individually dose tacrolimus are needed. Our objective was to determine whether a quantitative, dynamically-customized, phenotypic-outcome-guided dosing method termed Phenotypic Personalized Medicine (PPM) would improve target drug trough maintenance.

Methods

In a single-center, randomized, pragmatic clinical trial ( NCT03527238 ), 62 adults were screened, enrolled, and randomized prior to liver transplantation 1:1 to standard-of-care (SOC) clinician-determined or PPM-guided dosing of tacrolimus. The primary outcome measure was percent days with large (>2 ng/mL) deviation from target range from transplant to discharge. Secondary outcomes included percent days outside-of-target-range and mean area-under-the-curve (AUC) outside-of-target-range per day. Safety measures included rejection, graft failure, death, infection, nephrotoxicity, or neurotoxicity.

Results

56 (29 SOC, 27 PPM) patients completed the study. The primary outcome measure was found to be significantly different between the two groups. Patients in the SOC group had a mean of 38.4% of post-transplant days with large deviations from target range; the PPM group had 24.3% of post-transplant days with large deviations; (difference -14.1%, 95% CI: -26.7 to -1.5 %, P=0.029). No significant differences were found in the secondary outcomes. In post-hoc analysis, the SOC group had a 50% longer median length-of-stay than the PPM group [15 days (Q1-Q3: 11-20) versus 10 days (Q1-Q3: 8.5-12); difference 5 days, 95% CI: 2-8 days, P=0.0026].

Conclusions

PPM guided tacrolimus dosing leads to better drug level maintenance than SOC. The PPM approach leads to actionable dosing recommendations on a day-to-day basis.

Lay Summary

In a study on 62 adults who underwent liver transplantation, researchers investigated whether a new dosing method called Phenotypic Personalized Medicine (PPM) would improve daily dosing of the immunosuppression drug tacrolimus. They found that PPM guided tacrolimus dosing leads to better drug level maintenance than the standard-of-care clinician-determined dosing. This means that the PPM approach leads to actionable dosing recommendations on a day-to-day basis and can help improve patient outcomes.

Higher tacrolimus trough levels and time in the therapeutic range are associated with the risk of acute rejection in the first month after renal transplantation

BACKGROUND

Tacrolimus trough levels (C₀) are used in most transplant centres for therapeutic drug monitoring (TDM) of tacrolimus (Tac). The target range of Tac C₀ has been remarkably changed, with a target as low as 3-7 ng/ml in the 2009 European consensus conference and a target of 4-12 ng/ml (preferably to 7-12 ng/ml) following the second consensus report in 2019. Our aim was to investigate whether reaching early Tac therapeutic targets and maintaining time in the therapeutic range (TTR) according to the new recommendations may be necessary for preventing acute rejection (AR) during the first month after transplantation.

METHODS

A retrospective study including 160 adult renal transplant patients (113 men and 47 women) with a median age of 36.3 (20-44) years was conducted between January 2018 and December 2019 at 103 Military Hospital (Vietnam). Tac trough levels were recorded in the first month, and episodes of AR were confirmed by kidney biopsy. Tac TTR was calculated as the percentage of time within the target range of 7-12 ng/ml, according to the 2019 second consensus report. Multivariate Cox analysis was performed to identify the correlation between the Tac target range and TTR with AR.

RESULTS

In the first month after RT, 14 (8.8%) patients experienced AR. There was a significant difference in the incidence of AR between the Tac level groups of < 4, 4-7 and > 7 ng/ml (p = 0.0096). In the multivariate Cox analysis, after adjusting for related factors, a mean Tac level > 7 ng/ml was associated with an 86% decreased risk of AR compared with that of 4-7 ng/ml in the first month (HR, 0.14; 95% CI, 0.03-0.66; p = 0.0131). Every 10% increase in TTR was associated with a 28% lower risk of AR (HR, 0.72; 95% CI, 0.55-0.94; p = 0.014).

CONCLUSION

Gaining and maintaining Tac C₀ according to the 2019 second consensus report might reduce the risk of AR in the first month following transplantation.

Pharmacokinetic Evaluation of Tacrolimus in Chinese Adult Patients during the Early Stages Post-Lung Transplantation

BACKGROUND

Although tacrolimus has been widely used in patients undergoing lung transplantation, few studies have reported the pharmacokinetics of tacrolimus in Chinese patients after lung transplantation. Thus, we aimed to investigate the pharmacokinetics and influential factors in this patient cohort in the early stage after lung transplantation.

METHODS

We enrolled 14 adult lung transplant recipients who were treated with tacrolimus and then intensively collected blood samples within a 12-h dosing interval. The pharmacokinetic parameters of tacrolimus were calculated using non-compartmental analysis, and the influence of pathophysiological characteristics and CYP3A5*3 and CYP3A4*1G genotypes on the pharmacokinetics of tacrolimus was assessed. Using linear regression analysis, we investigated the correlation between tacrolimus concentration at different sampling points and measured the area under the time-concentration curve (AUC_0-12h).

RESULTS

Geometric mean of apparent clearance (CL/F) was 18.13 ± 1.65 L/h in non-CYP3A5*3/*3 carriers, five times higher than that in CYP3A5*3/*3 carriers (p < 0.001). Furthermore, the tacrolimus concentration 4 h after administration had the strongest correlation with AUC_0-12h (R² = 0.979).

CONCLUSION

The pharmacokinetics of tacrolimus varied largely between patients during the early stage post-transplantation, which could be partially explained by CYP3A5*3 genetic polymorphisms.

Differences in medication adherence by sex and organ type among adolescent and young adult solid organ transplant recipients

BACKGROUND

Identification of differences in medication adherence by sex or organ type may help in planning interventions to optimize outcomes. We compared immunosuppressive medication adherence between males and females, and between kidney, liver and heart transplant recipients.

METHODS

This multicenter study of prevalent kidney, liver and heart transplant recipients 14-25 years assessed adherence 3 times (0, 3, 6 months post-enrollment) with the BAASIS self-report tool. At each visit, participants were classified as adherent if they missed no doses in the prior 4 weeks and non-adherent otherwise. Adherence was also assessed using the coefficient of variation (CV) of tacrolimus trough levels; CV < 30% was classified as adherent. We used multivariable mixed effects logistic regression models adjusted for potential confounders to compare adherence by sex and by organ.

RESULTS

Across all visits, males (n = 150, median age 20.4 years, IQR 17.2-23.3) had lower odds of self-reported adherence than females (n = 120, median age 19.8 years, IQR 17.1-22.7) (OR 0.41, 95% CI 0.21-0.80) but higher odds of adherence by tacrolimus CV (OR 2.50, 95% CI 1.30-4.82). No significant differences in adherence (by self-report or tacrolimus CV) were noted between the 184 kidney, 58 liver, and 28 heart recipients.

CONCLUSION

Females show better self-reported adherence than males but greater variability in tacrolimus levels. Social desirability bias, more common in females than males, may contribute to better self-reported adherence among females. Higher tacrolimus variability among females may reflect biologic differences in tacrolimus metabolism between males and females rather than sex differences in adherence. There were no significant differences in adherence by organ type.

Education and Psychosocial Factors Predict Odds of Death After Transfer to Adult health Care in Pediatric Liver Transplant Patients

OBJECTIVES

To analyze demographic, psychosocial, and clinical factors in pediatric liver transplant recipients for their association with death or loss to follow up in adulthood. We aimed to better understand known health disparities in transplant outcomes and identify potentially modifiable risk factors prior to transfer.

METHODS

A retrospective cohort study of children who underwent liver transplantation at a large tertiary transplant center and were transferred to adult care between 2000 and 2015.

RESULTS

During the study period, 101 qualifying patients were transferred. Ninety-three individuals followed with an adult provider, while 8 were lost to follow up. In total 23 of 93 patients died after transfer (24.7%). Several childhood factors were associated with adult death: Black race [odds ratio (OR) 6.59, P < 0.001]; psychiatric illness or substance use (OR 2.81, P = 0.04); failure to graduate high school before transfer (OR 9.59, P < 0.001); posttransplant tacrolimus medication-level variability index >2.5 (OR 5.36, P = 0.04); provider documentation of medication nonadherence (OR 4.72, P = 0.02); acute cellular rejection (OR 4.44, P = 0.03); the presence of diabetes mellitus (OR 5.71, P = 0.001), and chronic kidney disease (OR 2.82, P = 0.04). Failure to graduate HS was associated with loss to follow up ( P < 0.001). On multivariate analysis, Black race, substance use, diabetes, and failure to graduate HS retained association with adult death (each P < 0.05).

CONCLUSIONS

Complex, intertwined patient characteristics are associated with increased odds of death in pediatric liver transplant recipients transferred to adult care. Early recognition of high-risk patients and intervention for modifiable factors, such as improved HS graduation and substance use prevention, may improve long-term outcomes.

Posttraumatic stress and medication adherence in pediatric transplant recipients

Adolescent transplant recipients may encounter a range of potentially traumatic events (PTEs) pre- and posttransplant, yet little is known about the relationship between posttraumatic stress symptoms (PTSS) and medication adherence in this population. In the present study, adolescent recipients and caregivers completed psychosocial questionnaires at enrollment. Outpatient tacrolimus trough level data were collected over 1 year to calculate the Medication Level Variability Index (MLVI), a measure of medication adherence. Nonadherence (MLVI ≥2) was identified in 34.8% of patients, and most (80.7%) reported ≥1 PTE exposure. Levels of PTSS indicating likely posttraumatic stress disorder (PTSD) were endorsed by 9.2% of patients and 43.7% of caregivers. PTSS and MLVI were significantly correlated in the liver subgroup (r = .30, p = .04). Hierarchical multivariable linear regression analyses revealed overall patient PTSS were significantly associated with QoL (p < .001). PTEs are common in adolescent recipients; a minority may meet criteria for PTSD. PTSS screening to identify nonadherence risk requires further investigation and addressing PTSS may improve QoL. Caregivers appear at greater risk for PTSD and may require their own supports. The study was approved by each participating center's Institutional Review Board.

The Role of Intra-Patient Variability of Tacrolimus Drug Concentrations in Solid Organ Transplantation: A Focus on Liver, Heart, Lung and Pancreas

Tacrolimus, the keystone immunosuppressive drug administered after solid organ transplantation, presents a narrow therapeutic index and wide inter- and intra-patient pharmacokinetic variability (IPV). The latter has been fairly studied in kidney transplantation, where it could impact outcomes. However, literature about other transplanted organ recipients remains inconclusive. This review aimed at summarizing the evidence about the IPV of tacrolimus concentrations outside of the scope of kidney transplantation. First, factors influencing IPV will be presented. Then, the potential of IPV as a biomarker predictive of graft outcomes will be discussed in liver, heart, lung and pancreas transplantation. Lastly, strategies to reduce IPV will be reviewed, with the ultimate objective being ready-to-implement solutions in clinical practice by transplantation professionals.

Association of intraindividual tacrolimus variability with de novo donor-specific HLA antibody development and allograft rejection in pediatric kidney transplant recipients with low immunological risk

BACKGROUND

Tacrolimus (Tac) intraindividual variability (TacIPV) in pediatric kidney transplant patients is only poorly understood. We investigated the impact of TacIPV on de novo donor-specific HLA antibodies (dnDSA) development and allograft rejection in Caucasian pediatric recipients of a living or deceased donor kidney with low immunological risk.

METHODS

This was a single-center retrospective study including 48 pediatric kidney transplant recipients. TacIPV was calculated based on coefficient of variation (CV%) 6-12 months posttransplant. TacIPV cutoff was set at the median (25%). Outcome parameters were dnDSA development and rejection episodes.

RESULTS

In total, 566 Tac levels were measured with median 11.0 (6.0-17.0) measurements per patient. The cutoff of 25% corresponded to the median CV% in our study cohort (25%, IQR 18-35%) and was comparable to cutoffs determined by receiver operating characteristic (ROC) curve analysis. High TacIPV was associated with higher risk of dnDSA development (HR 3.4, 95% CI 1.0-11.1, P = 0.047; Kaplan-Meier analysis P = 0.018) and any kind of rejection episodes (HR 4.1, 95% CI 1.1-14.8, P = 0.033; Kaplan-Meier analysis P = 0.010). There was a clear trend towards higher TacIPV below the age of 6 years. TacIPV (CV%) was stable over time. A TacIPV (CV%) cutoff of 30% or IPV quantification by mean absolute deviation (MAD) showed comparable results.

CONCLUSIONS

High TacIPV is associated with an increased risk of dnDSA development and rejection episodes > year 1 posttransplant even in patients with low immunological risk profile. Therefore, in patients with high TacIPV, potential causes should be addressed, and if not resolved, changes in immunosuppressive therapy should be considered. A higher resolution version of the Graphical abstract is available as Supplementary information.

Chronic rejection after liver transplantation: Opening the Pandora’s box

Chronic rejection (CR) of liver allografts causes damage to intrahepatic vessels and bile ducts and may lead to graft failure after liver transplantation. Although its prevalence has declined steadily with the introduction of potent immunosuppressive therapy, CR still represents an important cause of graft injury, which might be irreversible, leading to graft loss requiring re-transplantation. To date, we still do not fully appreciate the mechanisms underlying this process. In addition to T cell-mediated CR, which was initially the only recognized type of CR, recently a new form of liver allograft CR, antibody-mediated CR, has been identified. This has indeed opened an era of thriving research and renewed interest in the field. Liver biopsy is needed for a definitive diagnosis of CR, but current research is aiming to identify new non-invasive tools for predicting patients at risk for CR after liver transplantation. Moreover, the minimization or withdrawal of immunosuppressive therapy might influence the establishment of subclinical CR-related injury, which should not be disregarded. Therapies for CR may only be effective in the “early” phases, and a tailored management of the immunosuppression regimen is essential for preventing irreversible liver damage. Herein, we provide an overview of the current knowledge and research on CR, focusing on early detection, identification of non-invasive biomarkers, immunosuppressive management, re-transplantation and future perspectives of CR.

Tacrolimus trough levels in kidney transplant recipients

BACKGROUND

It is very important that kidney transplant recipients (KTRs) take immunosuppressive drugs to prevent graft rejection. This study aimed to identify the tacrolimus trough levels (TTL)-mean, TTL-standard deviation (SD), and TTL- coefficient of variation (CV) as well as factors affecting these values over a 2-year period in clinically stable patients > 5 years after kidney transplantation (KT).

METHODS

This retrospective study analyzed data from 248 adult outpatients > 5 years after KT. Medical chart data, including TTL, graft rejection, and tacrolimus dose change during a 2-year period, between January 2017 and December 2018, were collected. Multivariable regression analyses were conducted to determine the factors influencing the TTL-mean, TTL-SD, and TTL-CV.

RESULTS

The TTL-mean, TTL-SD, and TTL-CV were 6.00 ± 1.07 ng/mL, 1.51 ± 1.09 ng/mL, and 0.25 ± 0.14, respectively. The TTL-mean, TTL-SD, and TTL-CV did not differ according to sex, type of donor, retransplant, pretransplant kidney disease, body mass index, or posttransplant time; hence, they are stable in kidney transplant recipients > 5 years after KT. The higher the TTL-mean, the higher the TTL-SD. Age and the TTL-SD significantly predicted the TTL-mean (p < .001). Tacrolimus dose change and the TTL-mean significantly predicted the TTL-SD (p < .001). Tacrolimus dose change significantly predicted the TTL-CV (p = .008).

CONCLUSION

In clinically stable KTRs, TTL-SD and TTL-CV change sensitively in relation to tacrolimus dose changes. Therefore, changes in TTL-SD and TTL-CV in stable KTRs with no tacrolimus dose change require medical interest and attention.

FK506-loaded PLGA nanoparticles improve long-term survival of a vascularized composite allograft in a murine model

Background

The side effects of life-long administration of FK506 limit the clinical practice of vascularized composite allografts (VCAs). This study aimed to evaluate the feasibility of FK506-loaded poly (lactic-co-glycolic acid) (PLGA) nanoparticles (FK506 NPs) for prolonging the long-term survival of VCAs and reducing the side effects of FK506.

Methods

PLGA nanoparticles loaded with FK506 were prepared by the solvent evaporation method. The characterization of FK506 NPs was evaluated by electron microscopy. To confirm the function and safety of FK506 NPs, these particles were administrated into rats by intraperitoneal injection. The survival time of the allograft, systemic concentration of FK506, anti-rejection activity, and side-effect of FK506 NPs were evaluated in a Brown Norway (BN)-to-Sprague Dawley (SD) epigastric VCA transplantation model.

Results

Compared with the nontreatment, PLGA control and FK506 groups, the median survival times (MST) of the FK506 NP groups were significantly prolonged. The FK506 NPs could maintain therapeutic drug concentration for 60 days. Moreover, cytokine concentrations, flow cytometry of regulatory T cells (Tregs) and histopathology of allografts revealed significantly prolonged immunosuppression by FK506 NPs. FK506 NPs also ameliorated FK506 nephrotoxicity.

Conclusions

FK506 NPs prolong the survival time of VCAs in a murine model with minimal nephrotoxicity, and provide a potential clinical strategy for ameliorating long-term side effects of immunosuppressive therapy.

Impact of tacrolimus variability on pediatric heart transplant outcomes

BACKGROUND

Tacrolimus is a narrow therapeutic index drug, requiring consistent levels to maximize transplant success while reducing adverse effects. Elevated tacrolimus level variability (ETLV) is associated with poor outcomes in both pediatric and adult solid organ transplant recipients. We sought to describe the prevalence of ETLV and identify associations with patient-specific factors and poor outcomes.

METHODS

Tacrolimus levels were evaluated from 118 patients at our single center. As a marker of variability, standard deviations (SD) were calculated for each patient from their entire tacrolimus level data set (global SD), and 1-2 years and 1-5 years post-HT (prediction window SDs). SD ≥3 denoted ETLV.

RESULTS

There was large variability in tacrolimus levels (median global SD 3.1; IQR 2.3, 4; SD ≥3, n = 64, 54%). Patients with elevated SD (≥3) vs lower SD (<3) were more likely to have poor outcomes including rejection (73% vs 46%), cardiac allograft vasculopathy (CAV, 22% vs 9%), and death (20% vs 6%). The prediction window analysis noted ETLV was associated with a 40% greater risk of CAV, re-HT, or death (p = .024) and increasing age at transplantation was associated with a 12% increase in the risk of rejection (p = <.001) and a 19% increase in the risk of a composite event (p = .021).

CONCLUSION

ETLV is prevalent in the pediatric HT population with increased frequency of poor outcomes in those with SD ≥3. ETLV is an easily accessible marker with which to risk-stratify patients.

LIVER TRANSPLANTATION: TACROLIMUS BLOOD LEVELS VARIATION AND SURVIVAL, REJECTION AND DEATH OUTCOMES

BACKGROUND

Immunosuppressive drugs have important role in transplant of solid grafts, it aim avoid episodes of acute and chronic rejection and improving graft survival and patient survival. In Brazil, in 2016, liver transplantation was the third most frequent, with 1,880 transplants performed, of which 150 in Rio Grande do Sul. Several studies evaluated the association between variability in blood levels of immunosuppressive tacrolimus and late acute cellular graft rejection.

OBJECTIVE

To investigate the association of tacrolimus blood levels with clinical outcomes late acute cellular rejection, death, patient survival and graft survival in patients undergoing liver transplantation.

METHODS

This is a retrospective longitudinal study including patients submitted to adult liver transplantation by the Liver Transplantation Group in the Santa Casa de Misericórdia Hospital of Porto Alegre, from January 2006 to January 2013, and who used tacrolimus as immunosuppressive therapy.

RESULTS

Of the 127 patients included in the study, the majority were male (70.1%), 52-60 years old (33.9%) at the transplant. The most frequent causes of liver transplantation in this series were hepatitis C virus and hepatocellular carcinoma (24.4%) and alcohol (15.7%). Thirteen patients had late acute cellular rejection (10.2%); of these, three had two episodes. Regarding severity classification, seven patients had mild late acute cellular rejection. The mean time of rejection after liver transplantation was 14 months (ranging from 8 to 33 months). Overall survival was 8.98 years. Regarding tacrolimus blood levels, 52 patients with a variation ≥2 standard deviations were identified. Of these patients, eight had rejection; however, the association was not significant (P=0.146). A significant association was found between variation ≥2 standard deviations in tacrolimus blood levels and death (P=0.023) and survival (P=0.019). Regarding 5-year follow-up of graft survival, being two standard deviations above increases by 2.26 times the risk of transplanted graft loss, and for each unit of increase of standard deviation of tacrolimus blood levels there is a two-fold increase in the risk of graft loss in 5 years.

CONCLUSION

Increased risk of graft loss associated with increased standard deviations of tacrolimus blood levels may indicate the need for more rigorous and prospective monitoring of tacrolimus blood levels.

Impact of once-daily ER-Tac on trough concentration variability in a stable AYA renal transplant recipient cohort

BACKGROUND

Successful renal transplantation requires complex medication regimens that rely on strict adherence to be effective. Variability in immunosuppression exposure, specifically tacrolimus, is associated with poor allograft outcomes. Wide intra-patient variability of tacrolimus trough concentrations (Vtac) is likely, in part, attributable to regimen complexity and poor medication adherence. Once-daily tacrolimus formulations create opportunity to simplify therapeutic regimens, and this study aims to evaluate their impact on Vtac and ultimately transplant outcomes.

METHODS

This retrospective cohort study investigated stable (AYA) renal transplant recipients converted from (IR-Tac) to (ER-Tac). Subjects served as their own controls. Vtac was assessed by measuring the (SD) of serial tacrolimus trough concentrations prior to and at four time points post-conversion to ER-Tac over 24-month follow-up. Secondary outcome measures included graft function, infection rates, and effect on modifiable treatment-related factors.

RESULTS

Twenty-eight AYA subjects were converted from IR-Tac to ER-Tac. Vtac significantly improved following conversion and was sustained for 24 months (Vtac₀ 2.32 vs. Vtac₂₄ 1.11, p .017). Renal function remained stable, and (BPAR) rates were modest (14%). Mean pill burden was reduced by 15%, and 42.9% of subjects achieved a once-daily medication regimen.

CONCLUSIONS

Conversion from IR-Tac to ER-Tac in this AYA population significantly improved Vtac with sustained effect over 2 years. This effect is likely attributable in part to simplification of the medication regimen and presumably improved medication adherence. Such conversion does not appear to compromise graft function for at least 2 years post-conversion.

Effects of fasting on solid organ transplant recipients during Ramadan - a practical guide for healthcare professionals

Fasting in the month of Ramadan is an obligatory act for healthy adult Muslims. It requires abstinence from food and drink from dawn to sunset. Although there are exemptions from fasting, many patients are keen to fulfil what they see as a religious obligation, even if this may be against medical advice in some cases. Solid organ transplant (SOT) recipients often ask healthcare professionals for advice on fasting. Studies on the effect of fasting in transplant patients have all been done in the Middle East and North Africa where the average fasting duration is between 12 and 14 hours. In comparison, in temperate regions in the summer, fasting duration can be as long as 20 hours. Fasting when patients have to take immunosuppression 12 hours apart with little time variation poses unique challenges. In this review, current literature is reviewed, and a decision-making tool has been developed to assist clinicians in discussing the risks of fasting in transplant recipients, with consideration also given to circumstances such as the COVID-19 pandemic. Our review highlights that SOT recipients wishing to fast should undergo a thorough risk assessment, ideally 3 months before Ramadan. They may require medication changes and a plan for regular monitoring of graft function and electrolytes in order to fast safely. Recommendations have been based on risk tiers (very high risk, high risk and low/moderate risk) established by the International Diabetes Federation and the Diabetes and Ramadan International Alliance. Patients in the 'very high risk' and 'high risk' categories should be encouraged to explore alternative options to fasting such as winter fasting or Fidyah. Those in the 'low/moderate' category may be able to cautiously fast with guidance from their clinician. Prior to the commencement of Ramadan, all patients must receive up-to-date education on sick-day rules, instructions on when to terminate their fast or abstain from fasting.

Remote intervention engagement and outcomes in the Clinical Trials in Organ Transplantation in Children consortium multisite trial

Remote interventions are increasingly used in transplant medicine but have rarely been rigorously evaluated. We investigated a remote intervention targeting immunosuppressant management in pediatric lung transplant recipients. Patients were recruited from a larger multisite trial if they had a Medication Level Variability Index (MLVI) ≥2.0, indicating worrisome tacrolimus level fluctuation. The manualized intervention included three weekly phone calls and regular follow-up calls. A comparison group included patients who met enrollment criteria after the subprotocol ended. Outcomes were defined before the intent-to-treat analysis. Feasibility was defined as ≥50% of participants completing the weekly calls. MLVI was compared pre- and 180 days postenrollment and between intervention and comparison groups. Of 18 eligible patients, 15 enrolled. Seven additional patients served as the comparison. Seventy-five percent of participants completed ≥3 weekly calls; average time on protocol was 257.7 days. Average intervention group MLVI was significantly lower (indicating improved blood level stability) at 180 days postenrollment (2.9 ± 1.29) compared with pre-enrollment (4.6 ± 2.10), p = .02. At 180 days, MLVI decreased by 1.6 points in the intervention group but increased by 0.6 in the comparison group (p = .054). Participants successfully engaged in a long-term remote intervention, and their medication blood levels stabilized. NCT02266888.

Predicting acute rejection in children, adolescents, and young adults with a kidney transplant by assessing barriers to taking medication

BACKGROUND

Nonadherence to immunosuppression is common among pediatric, adolescent, and young adult kidney transplant recipients and a leading cause of graft loss. Assessing barriers to medication adherence in clinical practice may identify patients at risk for rejection and provide therapeutic targets.

METHODS

Kidney transplant patients and/or their caregivers were assessed for 14 barriers to medication adherence using the barriers assessment tool. We compared rejection rates between patients with at least one reported adherence barrier to those without reported adherence barriers using a Kaplan-Meier estimator and Cox proportional hazard models to adjust for other mediators of acute rejection at 2 years following barriers assessment.

RESULTS

Ninety-eight patients were assessed for barriers to adherence. Over the 2-year observation period, 22 patients developed biopsy-proven acute rejection (BPAR). Kaplan-Meier estimates show that patients with an identified barrier to adherence were more likely to have BPAR (p = 0.02) than patients without an identified barrier in the 24 months following barriers assessment. The median time to rejection for patients who experienced acute rejection was 175.5 days (IQR 63-276 days) from the time of barriers assessment. An identified barrier to adherence remained the only statistically significant predictor of BPAR with Cox modeling (HR 2.6, p = 0.04), after accounting for age, sex, and race.

CONCLUSIONS

Pediatric and adolescent kidney transplant recipients with identified adherence barriers are at increased risk for acute rejection. Barriers to adherence provide a potentially modifiable therapeutic target that can be assessed in clinic to guide targeted interventions.

Impact of CYP3A5 phenotype on tacrolimus time in therapeutic range and clinical outcomes in pediatric renal and heart transplant recipients

STUDY OBJECTIVE

This study investigated the effect of CYP3A5 phenotype on time in therapeutic range (TTR) of tacrolimus post-transplant in pediatric patients.

DESIGN AND DATA SOURCE

This retrospective study assessed medical records of pediatric kidney and heart recipients with available CYP3A5 genotype for tacrolimus dosing, troughs, and the clinical events (biopsy-proven acute rejection [BPAR] and de novo donor-specific antibodies [dnDSA]).

MEASUREMENTS AND MAIN RESULTS

The primary outcome, mean TTR in the first 90 days post-transplant, was 9.0% (95% CI: -16.1, -1.9) lower in CYP3A5 expressers (p = 0.014) when adjusting for time to therapeutic concentration and organ type. There was no difference between CYP3A5 phenotypes in time to the first clinical event using TTR during the first 90 days. When applying TTR over the first year, there was a significant difference in event-free survival (EFS) which was 50.0% for CYP3A5 expressers/TTR < 35%, 45.5% for expressers/TTR ≥ 35%, 38.1% for nonexpressers/TTR < 35%, and 72.9% for nonexpressers/TTR ≥ 35% (log-rank p = 0.03). A post hoc analysis of EFS identified CYP3A5 expressers had lower EFS compared to nonexpressers in patients with TTR ≥ 35% (p = 0.04) but no difference among patients with TTR < 35% (p = 0.6).

CONCLUSIONS

The relationship between TTR and CYP3A5 phenotype suggests that achieving a TTR ≥ 35% during the first year may be a modifiable factor to attenuate the risk of BPAR and dnDSA.

Retrospective Analysis of Tacrolimus Intrapatient Variability as a Measure of Medication Adherence

Background:

Increased intrapatient variability (IPV) in tacrolimus levels is associated with graft rejection, de novo donor-specific antibodies, and graft loss. Medication nonadherence may be a significant contributor to high IPV.

Objective:

The objective of this study is to determine the utility of tacrolimus IPV in detecting nonadherence by examining the relationship between self-reported adherence and tacrolimus coefficient of variability (COV), a measure of IPV.

Design:

Retrospective cohort study.

Setting:

St. Michael’s Hospital, Toronto, Ontario.

Patients:

All patients who were at least 1-year post-kidney transplant as of March 31, 2019, prescribed tacrolimus as an immunosuppressant and had a self-reported adherence status. Patients were excluded from the primary analysis of examining the correlation between COV and self-reported adherence if they lacked a calculatable COV.

Measurements:

Self-reported adherence, COV, demographic data, transplant, and medication history.

Methods:

A modified Basel Assessment of Adherence to Immunosuppressive Medications Scale (BAASIS) administered by healthcare professionals to assess self-reported adherence was used. The COV of tacrolimus trough levels was calculated and its correlation to BAASIS response was noted. The median COV was used as a cutoff to examine the characteristics of patients deemed “high COV” and “low COV.”

Results:

A total of 591 patients fit the initial criteria; however, only 525 had a recent calculatable COV. Overall, 92.38% of the population were adherent by self-report. Primary analysis identified a COV of 25.2% and 29.6% in self-reported adherent and nonadherent patients, respectively, though the result was not significant (P = .2). Secondary analyses showed a significant correlation between younger age at transplant and at the time of adherence self-reporting with nonadherence (P = .01). In addition, there was a strong correlation between those nonadherent with routine post-transplant blood work and younger age (P < .01).

Limitations:

The limitations included modified nonvalidated BAASIS questionnaire, social desirability bias, BAASIS only administered in English, and patients with graft failure not active in clinic not being captured.

Conclusions:

The COV should not be used as the sole method for determining medication adherence. However, COV may have some utility in capturing individuals who are not adherent to their blood work or patients who are having a poor response to tacrolimus and should be switched to another medication.

Adherence to laboratory testing in pediatric liver transplant recipients

BACKGROUND

The objectives of this retrospective cohort study are to describe rates of adherence to laboratory testing 6 months to 3 years post-liver transplantation and to examine demographic and clinical factors related to lab non-adherence and the association with medication adherence and clinical outcomes.

METHODS

Medical chart review was conducted for 54 youth (mean age = 5.0 years) transplanted between 2003 and 2014. Lab adherence (≥80%) was measured as the proportion of completed labs out of the number expected. Immunosuppressant drug-level variability was used as a proxy for medication adherence. Clinical outcomes included LAR, viral infection, hospitalization, and non-routine clinic visit ≥12 months after transplant.

RESULTS

Lab adherence decreased substantially over time. Single-parent household (aOR 5.86; 95% CI: 1.38-24.93) and no history of early rejection (aOR 3.96; 95% CI: 1.04-15.24) were independently associated with non-adherence. Lab non-adherence was significantly associated with medication non-adherence (P < .05), LAR (P = .02), and non-routine clinic visits (P = .03).

CONCLUSIONS

Systematic monitoring of lab adherence may help in identifying pediatric LT recipients at increased risk for excessive healthcare use and adverse outcomes possibly due to poor disease management.

Association Between Neighborhood-level Socioeconomic Deprivation and the Medication Level Variability Index for Children Following Liver Transplantation

BACKGROUND

Neighborhood socioeconomic deprivation is associated with adverse health outcomes. We sought to determine if neighborhood socioeconomic deprivation was associated with adherence to immunosuppressive medications after liver transplantation.

METHODS

We conducted a secondary analysis of a multicenter, prospective cohort of children enrolled in the medication adherence in children who had a liver transplant study (enrollment 2010-2013). Participants (N = 271) received a liver transplant ≥1 year before enrollment and were subsequently treated with tacrolimus. The primary exposure, connected to geocoded participant home addresses, was a neighborhood socioeconomic deprivation index (range 0-1, higher indicates more deprivation). The primary outcome was the medication level variability index (MLVI), a surrogate measure of adherence to immunosuppression in pediatric liver transplant recipients. Higher MLVI indicates worse adherence behavior; values ≥2.5 are predictive of late allograft rejection.

RESULTS

There was a 5% increase in MLVI for each 0.1 increase in deprivation index (95% confidence interval, -1% to 11%; P = 0.08). Roughly 24% of participants from the most deprived quartile had an MLVI ≥2.5 compared with 12% in the remaining 3 quartiles (P = 0.018). Black children were more likely to have high MLVI even after adjusting for deprivation (adjusted odds ratio 4.0 95% confidence interval, 1.7-10.6).

CONCLUSIONS

This is the first study to evaluate associations between neighborhood socioeconomic deprivation and an objective surrogate measure of medication adherence in children posttransplant. These findings suggest that neighborhood context may be an important consideration when assessing adherence. Differential rates of medication adherence may partly explain links between neighborhood factors and adverse health outcomes following pediatric liver transplantation.

TRANSITION of Pediatric Liver Transplant Patients to Adult Care: a Review

PURPOSE OF REVIEW

Many pediatric liver transplant patients are surviving to adulthood, and providers have come to recognize the importance of effectively transitioning these patients to an adult hepatologist. The review aims to analyze the most recent literature regarding patient outcomes after transition, barriers to successful transition, recommendations from clinicians and medical societies regarding transition programs, and to provide personal insights from our experience in transitioning liver transplant recipients.

RECENT FINDINGS

While results were variable between studies, many recent reports show significant morbidity and mortality in patients following transition to adult care. Medical non-adherence is frequently seen in adolescents and young adults both prior to and after transition, and is consistently associated with higher rates of rejection, graft loss, and death. In general, transplant programs with a formal transition process had better patient outcomes though recent findings are mostly-single center and direct comparison between programs is difficult. Societal recommendations for how to create a transition program contain a number of common themes that we have categorized for easier understanding. Successful transition is vital to the continued health of pediatric liver transplant patients. While an effective transition program includes a number of key components, it should be individualized to best function within a given transplant center. Here, we have reviewed a number of recent single-center retrospective studies on transition, but multi-site retrospective or prospective data is lacking, and is a fertile area for future research.

Tacrolimus intrapatient variability in solid organ transplantation: A multiorgan perspective

BACKGROUND

Tacrolimus therapy in solid organ transplant (SOT) recipients is challenging due to its narrow therapeutic window and pharmacokinetic variability both between patients and within a single patient. Intrapatient variability (IPV) of tacrolimus trough concentrations has become a novel marker of interest for predicting transplant outcomes. The purpose of this review is to evaluate the association of tacrolimus IPV with graft and patient outcomes and identify interventions to improve IPV in SOT recipients.

METHODS

A systematic review of the literature was performed using PubMed and Embase from database inception to September 20, 2020. Studies were eligible only if they evaluated an association between tacrolimus IPV and transplant outcomes. Both pediatric and adult studies were included. Measures of variability were limited to standard deviation, coefficient of variation, and time in therapeutic range.

RESULTS

Forty-four studies met the inclusion criteria. Studies were published between 2008 and 2020 and were observational in nature. Majority of data were published in adult kidney transplant recipients and identified an association with rejection, de novo donor specific antibody (dnDSA) formation, graft loss, and patient survival. Evaluation of IPV-directed interventions was limited to small preliminary studies.

CONCLUSIONS

High tacrolimus IPV has been associated with poor outcomes including acute rejection, dnDSA formation, graft loss, and patient mortality in SOT recipients. Future research should prospectively explore IPV-directed interventions to improve transplant outcomes.

Depression, Immunosuppressant Levels, and Clinical Outcomes in Postlung Transplant Recipients

OBJECTIVE

Posttransplant depression has been linked to increased risk for adverse outcomes in lung transplant patients. Maintaining target serum immunosuppressant levels is also essential for optimal lung transplant clinical outcome and may be a crucial predictor of outcomes. Because depression could affect medication nonadherence, resulting in out-of-range immunosuppressant levels, we examined the relationship between posttransplant depression, immunosuppressant medication trough level variability, indexed by out-of-range values on clinical outcomes and coefficient of variability, and clinical outcomes.

METHOD

A consecutive series of 236 lung transplant recipients completed the Center for Epidemiological Studies-Depression two-month posttransplant. Immunosuppressant trough levels (i.e., tacrolimus or cyclosporine) within the range of individualized immunosuppressant targets were obtained at three-, six-, nine-month follow-up clinic visits. Clinical outcomes including hospitalizations and mortality were obtained from medical records.

RESULTS

Fourteen percent of patients were classified as depressed (Center for Epidemiological Studies-Depression ≥16), 144 (61%) of patients had at least 25% out-of-range immunosuppressant values, and the average coefficient of variability was 36%. Over a median of 2.6 years (interquartile range = 1.2), 32 participants died (14%) and 144 (61%) had at least one unplanned, transplant-related hospitalization. Both depression (hazard ratio = 1.45 (1.19, 1.76), p < . 01) and immunosuppressant variation (immunosuppressant out-of-range: hazard ratio = 1.41 (1.10, 1.81), p < .01) independently predicted more frequent hospitalizations and higher mortality.

CONCLUSIONS

Early posttransplant depression was associated with significantly worse clinical outcomes. While immunosuppressant level variability is also related to adverse outcomes, such variability does not account for increased risk observed with depression.

Association of graft survival with tacrolimus exposure and late intra-patient tacrolimus variability in pediatric and young adult renal transplant recipients-an international CTS registry analysis

Adolescent and young adult age is a high-risk window with an alarmingly increased likelihood of premature kidney graft loss due to immunological rejection. Using the large database of the Collaborative Transplant Study, we analyzed whether a more intense and less variable exposure to tacrolimus could counteract this young age-related enhanced immunoreactivity. Kidney graft recipients aged 12-23 years (n = 964) with a 1-year tacrolimus trough level between 4.0 and 10.9 ng/ml had a 5-year graft survival rate of 85.1%, significantly better than the poor 66.1% rate in patients with a trough level below 4.0 ng/ml who showed a 2.38-fold increased risk of graft loss in the multivariable analysis (P < 0.001). This association was not apparent in young children aged 0-11 years (n = 455) and less pronounced in adults aged 24-34 years (n = 1466). However, an intra-patient variability of tacrolimus (IPV) trough level ≥1.5 at post-transplant years 1 and 2 was associated with an increased graft loss risk in both 12- to 23-year-old and 0- to 11-year-old recipients (P < 0.001 and P = 0.045). Patients with high IPV made up as many as 30% of kidney graft recipients, indicating that a more intense and less variable exposure to tacrolimus could improve graft survival strongly in this high-risk group.

High Intrapatient Variability in Tacrolimus Exposure Is Not Associated With Immune-mediated Graft Injury After Liver Transplantation

BACKGROUND

A high intrapatient variability (IPV) in tacrolimus exposure is associated with impaired long-term clinical outcome after kidney transplantation. It remains to be determined if this is equally detrimental for liver transplant recipients. The objective of this study was to investigate the association between IPV in tacrolimus exposure and immune-mediated graft injury after liver transplantation.

METHODS

For 326 liver transplant recipients, transplanted between 2000 and 2015, tacrolimus IPV was calculated from at least 5 tacrolimus trough samples obtained between months 6 and 18 after liver transplantation and expressed as the coefficient of variation. Primary composite endpoint consisted of immune-mediated graft injury (chronic rejection, biopsy proven, and suspected late acute rejection) after month 6. Secondary outcomes were the association between tacrolimus IPV on (1) loss of renal function per year of follow-up and (2) cytomegalovirus viremia after month 6.

RESULTS

Of the 326 included liver transplant recipients, 70 patients (21.5%) reached the primary endpoint. Median tacrolimus coefficient of variation was 28%. There was no significant difference in reaching the primary composite endpoint between the low- and high-IPV groups (P = 0.068). Model for End-Stage Liver Disease score pretransplantation and the number of acute rejections were identified as independent predictors for immune-mediated graft injury (P = 0.049 and 0.016). A higher IPV in combination with a low kidney function at baseline (estimated glomerular filtration rate < 40 mL/min) was associated with greater loss of renal function per year of follow-up (P = 0.007). Tacrolimus variability was not associated with late cytomegalovirus viremia.

CONCLUSIONS

High IPV in tacrolimus exposure beyond month 6 postliver transplantation was not associated with immune-mediated graft injury.

Caregivers' Barriers to Facilitating Medication Adherence in Adolescents/Young Adults With Solid Organ Transplants: Measure Development and Validation

OBJECTIVE

To evaluate the factor structure, validity, and reliability of the Caregiver Medication Barriers to Adherence Scale (CMBAS), which assesses caregivers' barriers to facilitating medication adherence in adolescent and young adults (AYAs) with solid organ transplants.

METHODS

The sample included 93 caregivers of AYAs ages 12-22 years who received a liver, kidney, or heart transplant. Caregivers completed the CMBAS and surveys to assess its validity, including internalizing symptoms, personality traits (i.e., neuroticism, conscientiousness), and AYAs' nonadherence to immunosuppressant medications. AYA nonadherence to tacrolimus was objectively assessed via the Medication Level Variability Index (MLVI).

RESULTS

Confirmatory factor analyses of the CMBAS revealed a two-factor model: Caregiver Emotional Distress and Caregiver Cognitive Burden/Responsibility. Higher CMBAS scores were related to higher levels of caregiver internalizing symptoms (rs = .28 to .30), neuroticism (r = .27), and caregiver proxy-reported immunosuppressant nonadherence (r = .27), as well as lower levels of caregiver conscientiousness (rs = -.25 to -.26). The CMBAS was not associated with the MLVI (rs = -.13 to -.16).

CONCLUSIONS

The CMBAS demonstrated reliability and validity for caregivers of AYAs with solid organ transplants. Findings support the use of the CMBAS as a brief clinical screening tool to identify caregivers' barriers to facilitating AYA medication adherence.

Late T cell-mediated rejection may contribute to poor outcomes in adolescents and young adults with liver transplantation

Although poor long-term graft survival in LT in AYA is recognized, detailed epidemiological data are still lacking. L-TCMR may have poor outcomes. This study aimed to provide a detailed, epidemiological assessment of the association between AYA age and rejection. L-TCMR was defined in this study as TCMR with central vein or perivenular inflammation occurring later than 3 months after LT. A total of 342 patients who survived for at least 3 months after LT between 2005 and 2015 were enrolled. The AYA group (10-24 years) was compared with the C group (less than 10 years), and the incidence and outcomes of L-TCMR were analyzed. In total, 342 patients had LT; 38 of these were AYA with the mean follow-up period of 6.7 years. A total of 304 patients in C group had a mean follow-up period of 6.3 years (P = .28). The incidence of L-TCMR in AYA group was significantly higher than in C group (15.8% vs 4.6%, P = .006). The time to L-TCMR after LT was significantly shorter in AYA group (P = .01). Neither patient survival nor the incidence of non-adherence differed significantly between the groups (P = .18 and P = .89). The number of additional immunosuppressants after L-TCMR was significantly higher in the AYA group (P = .04). A high incidence of L-TCMR was observed in AYA group irrespective of non-adherence. AYA patients with L-TCMR should be followed carefully due to the poor results of post-treatment biopsy and the need for intensive immunosuppressive therapy.

Tacrolimus variability is associated with de novo donor-specific antibody development in pediatric renal transplant recipients

BACKGROUND

Donor-specific antibody (DSA) is a risk factor for antibody-mediated rejection and shortened graft survival. We investigated the role of intrapatient variability in tacrolimus trough levels on graft outcomes (i.e., de novo DSA, rejection, graft loss) in pediatric renal transplant recipients.

METHODS

This was a single-center retrospective study which included 38 pediatric renal transplant recipients. Intrapatient tacrolimus variability was defined using the coefficient of variation (CV; SD/Mean × 100) for all levels obtained after 3 months post-transplant. CV cut-points of 30%, 40%, and 50% were used in the analyses.

RESULTS

The median CV 43.1% (35.0%, 58.6%). Out of 38 patients, 19 (50%) developed de novo DSA. In the logistic regression model, after adjusting for age, rejection history, maintenance immunosuppression, and CV, for every 10% increase in tacrolimus variability, the odds of developing de novo DSA increased by 53% (p = 0.048, CI 1.0005, 1.11). Age at transplant was also an independent risk factor for DSA development; every 1 year increase in age was associated with a 31% increase in the odds of developing DSA (p = 0.03, CI 1.03, 1.67). At a CV cut-point ≥ 30%, higher tacrolimus variability was associated with an increased incidence of allograft rejection (0% vs 42%, < 30 and ≥ 30% respectively, p = 0.07). As there were few graft loss events (n = 4) in our study population, an association could not be determined between tacrolimus variability and graft loss.

CONCLUSION

Tacrolimus variability and age at transplant were identified as independent risk factors for de novo DSA development. There was an association between tacrolimus variability and rejection in pediatric renal transplant recipients. Adding the assessment of tacrolimus variability to current monitoring methods may be an important step towards improving graft outcomes.

Assessment of rejection risk following subtherapeutic calcineurin inhibitor levels after pediatric heart transplantation

CNIs are the mainstay of immunosuppressive therapy after pediatric HTx. While regular laboratory surveillance is performed to ensure blood levels are within targeted range, the risk of acute rejection associated with subtherapeutic CNI levels has never been quantified. This is a retrospective single-center review of 8413 CNI trough levels in 138 pediatric HTx recipients who survived >1 year after HTx. Subtherapeutic CNI levels were defined as <50% of the lower limit of target range. The risk of acute, late (>12 months post-transplant) rejection following recipients' subtherapeutic CNI levels was assessed using time-varying multivariable Cox proportional hazards analysis. We found that 79 of 138 recipients (57%) had at least one subtherapeutic CNI level on routine surveillance laboratories during a mean follow-up of 5.5 ± 3.6 years. Following an episode of subtherapeutic levels, 17 recipients (22%) had biopsy-proven rejection within the next 3 months; the majority (9/17) within the first 2 weeks. After presenting with subtherapeutic CNI levels, recipients incurred a 6.1 times increased risk of acute rejection in the following 3 months (HR = 6.11 [2.41, 15.51], P = <.001). Age at HTx, HLA sensitization, or positive crossmatch were not associated with acute late rejection, but rejection in the first post-transplant year was (HR 2.61 [1.27, 5.35], P = .009). Thus, maintaining therapeutic CNI levels is the most important factor in preventing acute rejection in recipients who are >12 months after pediatric HTx. Recipients who present with subtherapeutic CNI levels on surveillance monitoring are 6.1 times more likely to develop rejection in the following 3 months.

Adherence, Medical Outcomes, and Health Care Costs in Adolescents/Young Adults Following Pediatric Liver Transplantation

OBJECTIVE

Improved outcomes after pediatric liver transplantation (LT) have led to increasing numbers of adolescent and young adult recipients entering into adult health care systems. The aim of this study was to evaluate the impact of transition from pediatric to adult health care models on medical outcomes, measures of adherence, and health care utilization for pediatric LT recipients.

METHODS

We evaluated the course of patients who received an LT while followed in pediatrics and transferred to an adult care provider within our institution. Data were collected from 2 years preceding and 2 years following transfer of care.

RESULTS

A total of 32 patients were eligible for analysis. Median age at time of transfer was 22.9 years (interquartile range 21.7-23.6). Nine patients (28%) died following transfer of care. There was a significant decrease in office visit adherence following transfer of care (P = 0.02). Although not achieving significance, an increase in alanine aminotransferase values, episodes of acute cellular rejection, progression to cirrhosis, evolution to chronic rejection, and hospital admission rates post transfer were found. These findings were associated with an increase in health care costs related to required interventions.

CONCLUSIONS

Our study demonstrates trends toward worse health outcomes, decreased adherence, and increased health care utilization following transfer of care. These findings and poor patient survival suggest that the time around transition from pediatric to adult health care models represents a period of increased vulnerability for pediatric LT recipients. Larger, multicenter, prospective studies are needed to identify factors and interventions that affect adolescent and young adult to improve the transition process.

Increasing Time in Therapeutic Range of Tacrolimus in the First Year Predicts Better Outcomes in Living-Donor Kidney Transplantation

Background: The aim of the present study was to investigate the impact of time in therapeutic range TTR on long-term outcomes of living kidney transplants.

Methods: We included 1,241 living kidney transplants and randomized them into development and validation cohorts with a ratio of 2:1. The tacrolimus TTR percentage was calculated by linear interpolation with a target range (5–10 ng/ml months 0–3, 4–8 ng/ml months 4–12). The optimal TTR cutoff was estimated by the receiver operating characteristic curve analysis on the basis of acute rejection (AR) within 12 months in the development cohort. Outcomes were analyzed between patients with high TTR and low TTR in the development and validation cohorts, respectively. The TTR was also compared with other tacrolimus measures.

Results: The optimal TTR cutoff value was 78%. In the development cohort, patients with TTR > 78% had significantly higher rejection- and infection-free survival. TTR < 78% was an independent risk factor for AR (OR: 2.97, 95%CI: 1.82–4.84) and infection (OR: 1.55, 95%CI: 1.08–2.22). Patient and graft survival were significantly higher in those with TTR>78%, and TTR<78% was associated with graft loss (OR: 3.2, 95%CI: 1.38–7.42) and patient death (OR: 6.54, 95%CI: 1.34–31.77). These findings were confirmed in the validation cohort. Furthermore, we divided all included patients into a high and low TTR group. TTR was more strongly associated with patient and graft survival than mean level, standard deviation, and intrapatient variability (IPV).

Conclusions: Increasing the TTR of tacrolimus in the first year was associated with improved long-term outcomes in living kidney transplants, and TTR may be a novel valuable strategy to monitor tacrolimus exposure.

A Novel, Dose-Adjusted Tacrolimus Trough-Concentration Model for Predicting and Estimating Variance After Kidney Transplantation

Background and Objective

Given that a high intrapatient variability (IPV) of tacrolimus whole blood concentration increases the risk for a poor kidney transplant outcome, some experts advocate routine IPV monitoring for detection of high-risk patients. However, attempts to estimate the variance of tacrolimus trough concentrations (TTC) are limited by the need for patients to receive a fixed dose over time and/or the use of linear statistical models. A goal of this study is to overcome the current limitations through the novel application of statistical methodology generalizing the relationship between TTC and dose through the use of nonparametric functional regression modeling.

Methods

With TTC as a response and dose as a covariate, the model employs an unknown bivariate function, allowing for the potentially complex, nonlinear relationship between the two parameters. A dose-adjusted variance of TTC is then derived based on standard functional principal component analysis (FPCA). To assess the model, it was compared against an FPCA-based model and linear mixed-effects models using prediction error, bias, and coverage probabilities for simulated data as well as phase III data from the Astellas new drug application studies for extended-release tacrolimus.

Results

Our numerical investigation indicates that the new model better predicts dose-adjusted TTCs compared with the prediction of linear mixed effects models. Estimated coverage probabilities also indicate that the new model accurately accounts for the variance of TTC during the periods of large fluctuation in dose, whereas the linear mixed effects model consistently underestimates the coverage probabilities because of the inaccurate characterization of TTC fluctuation.

Conclusion

This is the first known application of a functional regression model to assess complex relationships between TTC and dose in a real clinical setting. This new method has applicability in future clinical trials including real-world data sets due to flexibility of the nonparametric modeling approach.

Electronic supplementary material

The online version of this article (10.1007/s40268-019-0271-2) contains supplementary material, which is available to authorized users.

Defining a threshold for tacrolimus intra-patient variability associated with late acute cellular rejection in paediatric kidney transplant recipients

BACKGROUND

Late acute cellular rejection (LACR) is associated with poorer graft outcomes and non-adherence. Non-adherence to tacrolimus can be indirectly assessed by the intra-patient variability (IPV) of tacrolimus trough levels. The threshold of IPV associated with rejection is not known.

METHODS

We conducted a case-control study comparing 25 patients with biopsy-proven LACR against 25 stable controls matched for age group, primary diagnosis and time post-transplant. IPV was calculated using coefficient of variance (CV) and mean absolute deviation (MAD) using tacrolimus levels in the preceding 12 months. We also assessed the percentage time for tacrolimus levels < 4 μg/L (Tac < 4) and the concentration/weight-adjusted dose (C/D) ratio as a proxy marker of tacrolimus metaboliser status.

RESULTS

LACR patients had higher CV (median, IQR 44%, 36-61% v. 24%, 19-35%, p < 0.0001) and higher MAD (33%, 25-48% v. 19%, 15-26%, p < 0.0001). The MAD was less affected by outlying tacrolimus results. Receiver operating curve analysis of the MAD resulted in a sensitivity of 76% and specificity of 76% at a threshold of 26% (AUC 0.85, p < 0.05). LACR patients had more Tac < 4 (50% v. 26%, p < 0.05). There was no difference in C/D suggesting that good IPV can be maintained in fast metabolisers. Patients with LACR had significantly increased creatinine at 12-month follow-up despite treatment (108 v. 5 umol/L increase from baseline) and four patients lost their allograft.

CONCLUSIONS

Monitoring of tacrolimus IPV using the MAD may be a clinical marker for LACR. A threshold IPV of 26% can potentially be used as a therapeutic target pending further validation studies.

Multimethod Assessment of Medication Nonadherence and Barriers in Adolescents and Young Adults With Solid Organ Transplants

Objective

To (a) examine levels of medication nonadherence in adolescent and young adult (AYA) solid organ transplant recipients based on AYA- and caregiver proxy-reported nonadherence to different medication types and the medication-level variability index (MLVI) for tacrolimus, and (b) examine associations of adherence barriers and AYA and caregiver emotional distress symptoms with reported nonadherence and the MLVI.

Method

The sample included 47 AYAs (M age = 16.67 years, SD = 1.74; transplant types: 25% kidney, 47% liver, 28% heart) and their caregivers (94 total participants). AYAs and caregivers reported on AYAs' adherence barriers and their own emotional functioning. Nonadherence was measured with AYA self- and caregiver proxy-report and the MLVI for tacrolimus.

Results

The majority of AYAs and caregivers denied nonadherence, with lower rates of nonadherence reported for antirejection medications. In contrast, 40% of AYAs' MLVI values indicated nonadherence to tacrolimus. AYAs and caregivers who verbally acknowledged nonadherence had more AYA barriers and greater caregiver emotional distress symptoms compared with those who denied nonadherence. AYAs with MLVIs indicating nonadherence had more barriers than AYAs with MLVIs indicating adherence.

Conclusions

Multimethod nonadherence evaluations for AYA transplant recipients should assess objective nonadherence using the MLVI, particularly in light of low reported nonadherence rates for antirejection medications. Assessments should include adherence barriers measures, given associations with the MLVI, and potentially prioritize assessing barriers over gauging nonadherence via self- or proxy-reports. Caregiver emotional distress symptoms may also be considered to provide insight into family or environmental barriers to adherence.