African American Kidney Transplant Recipients Research Articles

Extreme phenotype sampling and next generation sequencing to identify genetic variants associated with tacrolimus in African American kidney transplant recipients.

African American (AA) kidney transplant recipients (KTRs) have poor outcomes, which may in-part be due to tacrolimus (TAC) sub-optimal immunosuppression. We previously determined the common genetic regulators of TAC pharmacokinetics in AAs which were CYP3A5 *3, *6, and *7. To identify low-frequency variants that impact TAC pharmacokinetics, we used extreme phenotype sampling and compared individuals with extreme high (n = 58) and low (n = 60) TAC troughs (N = 515 AA KTRs). Targeted next generation sequencing was conducted in these two groups. Median TAC troughs in the high group were 7.7 ng/ml compared with 6.3 ng/ml in the low group, despite lower daily doses of 5 versus 12 mg, respectively. Of 34,542 identified variants across 99 genes, 1406 variants were suggestively associated with TAC troughs in univariate models (p-value < 0.05), however none were significant after multiple testing correction. We suggest future studies investigate additional sources of TAC pharmacokinetic variability such as drug-drug-gene interactions and pharmacomicrobiome.

Assessing the Utility of a Genotype-Guided Tacrolimus Equation in African American Kidney Transplant Recipients: A Single Institution Retrospective Study.

Tacrolimus metabolism is heavily influenced by the CYP3A5 genotype, which varies widely among African Americans (AA). We aimed to assess the performance of a published genotype-informed tacrolimus dosing model in an independent set of adult AA kidney transplant (KTx) recipients. CYP3A5 genotypes were obtained for all AA KTx recipients (n = 232) from 2010 to 2019 who met inclusion criteria at a single transplant center in Philadelphia, Pennsylvania, USA. Medical record data were used to calculate predicted tacrolimus clearance using the published AA KTx dosing equation and two modified iterations. Observed and model-predicted trough levels were compared at 3 days, 3 months, and 6 months post-transplant. The mean prediction error at day 3 post-transplant was 3.05 ng/mL, indicating that the model tended to overpredict the tacrolimus trough. This bias improved over time to 1.36 and 0.78 ng/mL at 3 and 6 months post-transplant, respectively. Mean absolute prediction error-a marker of model precision-improved with time to 2.33 ng/mL at 6 months. Limiting genotype data in the model decreased bias and improved precision. The bias and precision of the published model improved over time and were comparable to studies in previous cohorts. The overprediction observed by the published model may represent overfitting to the initial cohort, possibly limiting generalizability.

Impact of CYP3A5 Status on the Clinical and Financial Outcomes Among African American Kidney Transplant Recipients.

Background.Pharmacogenetic profiling of transplant recipients demonstrates that the marked variation in the metabolism of immunosuppressive medications, particularly tacrolimus, is related to genetic variants. Patients of African ancestry are less likely to carry loss-of-function (LoF) variants in the CYP3A5 gene and therefore retain a rapid metabolism phenotype and higher clearance of tacrolimus. Patients with this rapid metabolism typically require higher dosing to achieve therapeutic trough concentrations. This study aims to further characterize the impact of CYP3A5 genotype on clinical outcomes and financial expenditure.Methods.The CYP3A5 phenotype status was identified in 438 adult kidney transplant (KTx) recipients (96% were African American) using 3 LoF alleles (CYP3A5*3, *6 or *7). Individuals were categorized as rapid metabolism phenotype without LoF alleles‚ intermediate phenotype for 1 LoF allele‚ and slow phenotype for 2 LoF alleles. KTx outcomes (patient/kidney survival and Medicare spending) were determined using linked transplant registry and claims data.Results.Among the cohort, 23% had a rapid, 47% intermediate, and 30% a slow metabolism phenotype based on genotype. At 3 y, the rate of death censored graft failure and all cause graft failure was highest in the rapid metabolism phenotype and lowest in the intermediate metabolism phenotype group. First-year Medicare reimbursement differed significantly by genotype (rapid: $79 535, intermediate: $72 796, slow: $79 346, P = 0.03). After adjustment for donor and recipient characteristics, care for patients with intermediate metabolism was $4790 less expensive (P = 0.003).Conclusions.Pharmacogenomic assessment of African American KTx recipients may be useful to guide therapy when as CYP3A5 functional variants appear to be associated with differential outcome and spending after transplant.

Acute Kidney Injury in a Predominantly African American Cohort of Kidney Transplant Recipients With COVID-19 Infection.

Renal involvement in severe or critical acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is frequent. Acute kidney injury (AKI) in African American (AA) kidney transplant recipients (KTRs) with COVID-19 is not well described. We report our experience with a predominantly AA cohort (79%) of KTRs with COVID-19 infections in the Detroit Metropolitan area. In this retrospective, single-center study, we identified 39 KTRs who tested positive for SARS-CoV-2 between March 16 and April 25, 2020. Data from electronic medical records were retrieved and compared between KTRs without AKI and KTRs with AKI. One patient was excluded due to delayed graft function. Final analysis of AKI in KTRs with proven COVID-19 was done on 38 patients of which 30 were AA (79%). AKI occurred in 71.1% of COVID-19 KTRs (n = 27), of whom 6 (22.2%) patients required HD. The incidence of AKI in our cohort was 71% (27/38). AKI rate among AA was 76.7% versus 50% in non-AA cohort (P = 0.195). In a univariate logistic regression analysis, AA race was not significantly associated with AKI odds ratio (3.4; CI, 0.68-17.4; P = 0.14). After risk adjustment by race, patients with diabetes showed a significantly higher risk of AKI (adjusted odds ratio, 19.85; CI, 1.65-58.66; P = 0.012). KTRs with AKI had more preexisting renin angiotensin aldosterone system inhibitor use than KTRs without AKI (P = 0.03). KTRs infected with SARS-CoV-2 have a high incidence of AKI, with associated increased morbidity and mortality. Although no racial differences in mortality were noted in our KTRs with AKI, we await data from registries to help elucidate this difference.

Dosing Requirements of Extended-Release Tacrolimus (Astagraf XL) in African American Kidney Transplant Recipients Converted from Immediate-Release Tacrolimus (AAAKTRS).

The formal recommendation for converting twice-daily tacrolimus immediate release (IR) to once-daily tacrolimus extended release (ER) is a 1:1 dose conversion. However, more recent clinical analysis has shown that this may not be true; some patients may require a higher dose. In addition, de novo dosing tacrolimus ER has revealed that African Americans require approximately 20%-30% higher doses than Caucasians to achieve similar levels. As a result, this study sought to identify the appropriate dose conversion in the African American kidney transplant population, a population at high risk of rejection. This was a single-center, prospective, open-label study comparing the difference in dose-normalized trough and total daily dose necessary to reach steady-state therapeutic goal, after conversion from tacrolimus IR to tacrolimus ER, in 25 African American kidney transplant recipients. After conversion to tacrolimus ER, there was a significant decrease in dose-normalized trough (C0) (0.44 versus 0.59, P = 0.03). Statistically significant differences were seen in both total daily and weight-based doses, when reported as actual values (15 versus 10 mg and 0.16 versus 0.11 mg/kg, respectively), as well as when standardized to achieve a target tacrolimus C0 of 8 ng/mL (18.1 versus 13.6 mg and 0.17 versus 0.15 mg/kg, respectively). The median standardized dose conversion required was 1.3 [1.0, 1.4], for the overall population. There were no instances of biopsy-proven acute rejection, allograft loss, or study drug discontinuation. This single-center, open-label conversion study demonstrated that there was a statistically and clinically significant decrease in dose-normalized trough after conversion from tacrolimus IR to tacrolimus ER in an African American kidney transplant population and that a 1:1 dose conversion is unlikely to meet therapeutic goals.

The impact of time-varying clinical surrogates on disparities in African-American kidney transplant recipients - a retrospective longitudinal cohort study.

An improved understanding of the impact of clinical surrogates on disparities in African-American (AA) kidney transplantation (KTX) is needed. We conducted a 10-year retrospective longitudinal cohort study of electronically abstracted clinical data assessing the impact of surrogates on disparities in KTX. Clinical surrogates were assessed by posttransplant year (1, 2, 3 or 4) and defined as acute rejection (Banff ≥1A), mean SBP >140mmHg, tacrolimus variability (CV) >40%, mean glucose >160mg/dl and mean hemoglobin <10g/dl. We utilized landmark methodology to minimize immortal time bias and logistic and survival regression to assess outcomes; 1610 KTX were assessed (54.2% AAs), with 1000, 468, 368 and 303 included in the year 1, 2, 3 and 4 complete case analyses, respectively. AAs had significantly higher odds of developing a clinical surrogate, which increased in posttransplant years three and four [OR year 1 1.99 (1.38-2.88), year 2 1.77 (1.20-2.62), year 3 2.35 (1.49-3.71), year 4 2.85 (1.72-4.70)]. Adjusting for the five clinical surrogates in survival models explained a significant portion of the higher risks of graft loss in AAs in post-transplant years three and four. Results suggest focusing efforts on improving late clinical surrogate management within AAs may help mitigate racial disparities in KTX.

Pharmacist-Led, Technology-Assisted Study to Improve Medication Safety, Cardiovascular Risk Factor Control, and Racial Disparities in Kidney Transplant Recipients.

Health disparities in African-American (AA) kidney transplant recipients compared with non-AA recipients are well established. Cardiovascular disease (CVD) risk control is a significant mediator of this disparity. To assess the efficacy of improved medication safety, CVD risk control, and racial disparities in kidney transplant recipients. Prospective, pharmacist-led, technology-aided, 6-month interventional clinical trial. A total of 60 kidney recipients with diabetes and hypertension were enrolled. Patients had to be at least one-year post transplant with stable graft function. Primary outcome measured included hypertension, diabetes, and lipid control using intent-to-treat analyses, with differences assessed between AA and non-AA recipients. The participants mean age was 59 years, with 42% being female and 68% being AA. Overall, patients demonstrated improvements in blood pressure <140/90 mmHg (baseline 50% vs. end of study 68%, p=0.054) and hemoglobin A1c <7% (baseline 33% vs. end of study 47%, p=0.061). AAs demonstrated a significant reduction from baseline in systolic blood pressure (-0.86 mmHg per month, p=0.026), which was not evident in non-AAs (-0.13 mmHg per month, p=0.865). Mean HgbA1c decreased from baseline in the overall group (-0.12% per month, p=0.003), which was similar within AAs (-0.11% per month, p=0.004) and non-AAs (-0.14% per month, p=0.029). There were no changes in low-density lipoproteins, triglycerides, or high-density lipoproteins over the course of the study. Medication errors were significantly reduced and self-reported medication adherence significantly improved over the course of the study. These results demonstrate the potential efficacy of a pharmacist-led, technology-aided, educational intervention in improving medication safety, diabetes, and hypertension and reducing racial disparities in AA kidney transplant recipients. (ClinicalTrials.gov NCT02763943).

Transplant Center Variability in Disparities for African-American Kidney Transplant Recipients.

BackgroundDisparities research has traditionally focused on patient-level variables to ascertain predominant risk factors driving differences in outcomes for African-American (AA) kidney transplant recipients. Our objectives were to determine the magnitude and impact of transplant center variability for graft outcome disparities.Material/MethodsThis was a retrospective cohort study analyzing 25 years of U.S. national transplant registry data at both the patient and center levels using univariate descriptive statistics and multivariable modeling.ResultsA total of 257,024 recipients from 191 centers were analyzed; AAs represented 31.1% of recipients. After adjusting for baseline characteristics, AAs had 42% higher risk of graft loss (aHR 1.42, 95% CI 1.39 to 1.45; p<0.001). Center variability for graft outcome disparities in AAs was significant (race*center interaction term p<0.05), with the aHRs ranging from 0.5 to 4.9; 46% of centers demonstrated a non-statistically significant disparity (aHR p>0.05) and 25% of centers had a large AA disparity (aHR >1.75). In a more recent transplant time period (2000–14), overall racial disparities decreased but center-level disparities increased in variability. Center-level factors significantly associated with increasing disparity included higher acute rejection rates, fewer transplants per year, longer length of stay, lower use of calcineurin inhibitors (CNI), and lower living donor rates.ConclusionsThere is evidence of significant center-level variability in graft outcome disparities for AA kidney recipients. Further, there appears to be a number of center-level factors associated with this variability, including acute rejection rates, CNI use, number of transplants per year, and, in recent years, low living donor rates.

Impact of CYP3A5 genomic variances on clinical outcomes among African American kidney transplant recipients.

Little is known about the impact of CYP3A5 polymorphisms on transplantation outcomes among African American (AA) kidney transplant recipients (KTRs). To assess this issue, clinical outcomes were compared between AA CYP3A5*1 expressers and nonexpressers. This retrospective cohort study analyzed AA KTRs. Biopsy-proven acute rejection (BPAR), delayed graft function (DGF), glomerular filtration rate (GFR), infections, and tacrolimus dosing requirements were examined in 106 immunologically high-risk AA kidney transplant patients over a 2-year follow-up period. In CYP3A5*1 expressers compared to nonexpressers, the incidence of BPAR was significantly higher in the first 6months (13% vs 0%; P=.016) compared to 24months (13% vs 7%; P=.521). Tacrolimus total daily dose at first therapeutic level was significantly higher in CYP3A5*1 expressers (12mg/day) compared to nonexpressers (8mg/day; P<.001). Compared to CYP3A5*1 nonexpressers, DGF incidence was significantly higher among CYP3A5*1 expressers (27.6% vs 6.7%; P=.006). By contrast, median GFR was significantly higher in CYP3A5*1 expressers compared to nonexpressers (54.5mL/min vs 50.0mL/min; P=.003) at 24months. The findings from this retrospective study suggest that AAs with CYP3A5*1 expression require 50% more tacrolimus and have an increased incidence of DGF and acute rejection.

Tacrolimus Trough Concentration Variability and Disparities in African American Kidney Transplantation.

Low tacrolimus concentrations have been associated with higher risk of acute rejection, particularly within African American (AA) kidney transplant recipients; little is known about intrapatient tacrolimus variabilities impact on racial disparities. Ten year, single-center, longitudinal cohort study of kidney recipients. Intrapatient tacrolimus variability was assessed using the coefficient of variation (CV) measured between 1 month posttransplant and the clinical event, with a comparable period assessed in those without events. Pediatrics, nontacrolimus/mycophenolate regimens, and nonrenal transplants were excluded. Multivariable Cox regression models were used to analyze data. One thousand four hundred eleven recipients were included (54.4% AA) with 39 521 concentrations used to assess intrapatient tacrolimus CV. Overall, intrapatient tacrolimus CV was higher in AAs versus non-AAs (39.9 ± 19.8 % vs 34.8 ± 15.8% P < 0.001). Tacrolimus variability was a significant risk factor for deleterious clinical outcomes. A 10% increase in tacrolimus CV augmented the risk of acute rejection by 20% (adjusted hazard ratio, 1.20, 1.13-1.28; P < 0.001) and the risk of graft loss by 30% (adjusted hazard ratio, 1.30, 1.23-1.37; P < 0.001), with significant effect modification by race for acute rejection, but not graft loss. High tacrolimus variability (CV >40%) was a significant explanatory variable for disparities in AAs; the crude relative risk of acute rejection in AAs was reduced by 46% when including tacrolimus variability in modeling and reduced by 40% for graft loss. These data demonstrate that intrapatient tacrolimus variability is strongly associated with acute rejection in AAs and graft loss in all patients. Tacrolimus variability is a significant explanatory variable for disparities in AA recipients.

Improving Medication Safety and Cardiovascular Risk Factor Control to Mitigate Disparities in African-American Kidney Transplant Recipients: Design and Methods.

There is a lack of data analyzing the influence of cardiovascular disease (CVD) risk factor control on graft survival disparities in African-American kidney transplant recipients. Studies in the general population indicate that CVD risk factor control is poor in African-Americans, leading to higher rates of renal failure and major acute cardiovascular events. However, with the exception of hypertension, there is no data demonstrating similar results within transplant recipients. Recent analyses conducted by our investigator group indicate that CVD risk factors, especially diabetes, are poorly controlled in African-American recipients, which likely impacts graft loss. This study protocol describes a prospective interventional clinical trial with the goal of demonstrating improved medication safety and CVD risk factor control in adult solitary kidney transplant recipients at least one-year post-transplant with a functioning graft. This is a prospective, interventional, 6-month, pharmacist-led and technology enabled study in adult kidney transplant recipients with the goal of improving CVD risk factor outcomes by improving medication safety and patient self-efficacy. This papers describes the issues related to racial disparities in transplant, the details of this intervention and how we expect this intervention to improve CVD risk factor control in kidney transplant recipients, particularly within African-Americans.

Results of ASERTAA, a Randomized Prospective Crossover Pharmacogenetic Study of Immediate-Release Versus Extended-Release Tacrolimus in African American Kidney Transplant Recipients

Differences in tacrolimus dosing across ancestries is partly attributable to polymorphisms in CYP3A5 genes that encode tacrolimus-metabolizing cytochrome P450 3A5 enzymes. The CYP3A5*1 allele, preponderant in African Americans, is associated with rapid metabolism, subtherapeutic concentrations, and higher dose requirements for tacrolimus, all contributing to worse outcomes. Little is known about the relationship between CYP3A5 genotype and the tacrolimus pharmacokinetic area under the curve (AUC) profile in African Americans or whether pharmacogenetic differences exist between conventional twice-daily, rapidly absorbed, immediate-release tacrolimus (IR-Tac) and once-daily extended-release tacrolimus (LifeCycle Pharma Tac [LCPT]) with a delayed absorption profile. Randomized prospective crossover study. 50 African American maintenance kidney recipients on stable IR-Tac dosing. Recipients were randomly assigned to continue IR-Tac on days 1 to 7 and then switch to LCPT on day 8 or receive LCPT on days 1 to 7 and then switch to IR-Tac on day 8. The LCPT dose was 85% of the IR-Tac total daily dose. Tacrolimus 24-hour AUC (AUC0-24), peak and trough concentrations (Cmax and Cmin), time to peak concentration, and bioavailability of LCPT versus IR-Tac, according to CYP3A5 genotype. CYP3A5 genotype, 24-hour tacrolimus pharmacokinetic profiles. ∼80% of participants carried the CYP3A5*1 allele (CYP3A5 expressers). There were no significant differences in AUC0-24 or Cmin between CYP3A5 expressers and nonexpressers during administration of either IR-Tac or LCPT. With IR-Tac, tacrolimus Cmax was 33% higher in CYP3A5 expressers compared with nonexpressers (P=0.04): With LCPT, this difference was 11% (P=0.4). This was primarily a pharmacogenetic study rather than an efficacy study; the follow-up period was too short to capture clinical outcomes. Achieving therapeutic tacrolimus trough concentrations with IR-Tac in most African Americans results in significantly higher peak concentrations, potentially magnifying the risk for toxicity and adverse outcomes. This pharmacogenetic effect is attenuated by delayed tacrolimus absorption with LCPT. Registered at ClinicalTrials.gov, with study number NCT01962922.

Prevalence of CYP3A5 Genomic Variances and Their Impact on Tacrolimus Dosing Requirements among Kidney Transplant Recipients in Eastern North Carolina.

To assess the prevalence of CYP3A5 genomic variances and their impact on tacrolimus (TAC) dosing requirements among kidney transplant recipients in eastern North Carolina, we conducted a single-center retrospective cohort study at a large tertiary care medical center. A total of 162 adults who received a kidney transplant between March 1, 2013, and February 28, 2015, and received oral TAC as part of their maintenance immunosuppression were enrolled. Of these patients, 85 patients expressed a genotype with a CYP3A5*1 variant (CYP3A5*1 group), and 77 patients expressed genotypes with other CYP3A5 variants (nonexpressor group). All patients were followed for 1 year posttransplantation. The primary end point was the TAC total daily dose (TDD) required to achieve the first therapeutic trough level based on the presence or absence of the CYP3A5*1 variant. The prevalence of different CYP3A5 variants across race/ethnicities in the study cohort was determined by CYP3A5 genotyping for each patient. The CYP3A5*1 and nonexpressor groups did not differ significantly with respect to sex, mean age, or mean weight. The CYP3A5*1 group was largely African American (93%, p≤0.0005) compared with other race/ethnicities. Among the CYP3A5*1 expressors compared with nonexpressors, the mean TAC TDD in milligrams at the first therapeutic TAC level was significantly higher (12 vs 8 mg/day, p≤0.001). Similarly, the mean TAC TDD in milligrams/kilogram was 50% greater among CYP3A5*1 expressors (0.15 vs 0.1 mg/kg/day, p≤0.0005). The predominant genotypic variants were CYP3A5*3/*3 (33%), CYP3A5*1/*3 (20%), and CYP3A5*1/*1 (19%). This study illustrates the prevalence of the CYP3A5*1 variant among African-American kidney transplant recipients and the effect of this gene expression on the TAC TDD. Patients with the CYP3A5*1 variant require higher TAC doses, on average, to achieve desirable drug levels. In addition, this study provides transplant clinicians with insight and support to dose TAC more aggressively in African-American kidney transplant recipients who may be at higher risk for both toxicities as well as poor clinical outcomes related to inadequate immunosuppression.

Twenty years of evolving trends in racial disparities for adult kidney transplant recipients

Disparities in outcomes for African American (AA) kidney transplant recipients have persisted for 40 years without a comprehensive analysis of evolving trends in the risks associated with this disparity. Here we analyzed U.S. transplant registry data, which included adult Caucasian or AA solitary kidney recipients undergoing transplantation between 1990 and 2009 comprising 202,085 transplantations. During this 20-year period, the estimated rate of 5-year graft loss decreased from 27.6% to 12.8%. Notable trends in baseline characteristics that significantly differed by race over time included the following: increased prevalence of diabetes from 2001 to 2009 in AAs (5-year slope difference: 3.4%), longer time on the waiting list (76.5 more days per 5 years in AAs), fewer living donors in AAs from 2003 to 2009 (5-year slope difference: -3.36%), more circulatory death donors in AAs from 2000-09 (5-year slope difference: 1.78%), and a slower decline in delayed graft function in AAs (5-year slope difference: 0.85%). The absolute risk difference between AAs and Caucasians for 5-year graft loss significantly declined over time (-0.92% decrease per 5 years), whereas the relative risk difference actually significantly increased (3.4% increase per 5 years). These results provide a mixed picture of both promising and concerning trends in disparities for AA kidney transplant recipients. Thus, although the disparity for graft loss has significantly improved, equity is still far off, and other disparities, including living donation rates and delayed graft function rates, have widened during this time.

Quantifying the Race Stratified Impact of Socioeconomics on Graft Outcomes in Kidney Transplant Recipients.

Socioeconomic status (SES) is a significant determinant of health outcomes and may be an important component of the causal chain surrounding racial disparities in kidney transplantation. The social adaptability index (SAI) is a validated and quantifiable measure of SES, with a lack of studies analyzing this measure longitudinally or between races. Longitudinal cohort study in adult kidney transplantation transplanted at a single-center between 2005 and 2012. The SAI score includes 5 domains (employment, education, marital status, substance abuse and income), each with a minimum of 0 and maximum of 3 for an aggregate of 0 to 15 (higher score → better SES). One thousand one hundred seventy-one patients were included; 624 (53%) were African American (AA) and 547 were non-AA. African Americans had significantly lower mean baseline SAI scores (AAs 6.5 vs non-AAs 7.8; P < 0.001). Cox regression analysis demonstrated that there was no association between baseline SAI and acute rejection in non-AAs (hazard ratio [HR], 0.92; 95% confidence interval [95% CI], 0.81-1.05), whereas it was a significant predictor of acute rejection in AAs (HR, 0.89; 95% CI, 0.80-0.99). Similarly, a 2-stage approach to joint modelling of time to graft loss and longitudinal SAI did not predict graft loss in non-AAs (HR, 1.01; 95% CI, 0.28-3.62), whereas it was a significant predictor of graft loss in AAs (HR, 0.23; 95% CI, 0.06-0.93). After controlling for confounders, SAI scores were associated with a lower risk of acute rejection and graft loss in AA kidney transplant recipients, whereas neither baseline nor follow-up SAI predicted outcomes in non-AA kidney transplant recipients.

A randomized, prospective comparison of transition to sirolimus-based CNI-minimization or withdrawal in African American kidney transplant recipients.

There is a lack of conclusive evidence to suggest if calcineurin inhibitor (CNI) withdrawal or minimization with sirolimus is the best strategy for African Americans. This was a randomized, prospective, open-label, pilot study comparing the two mammalian target of rapamycin (mTOR) transition strategies in adult African Americans between six and 24 wk post-transplant. The primary outcome was a comparison of the eGFR at one yr after conversion. Forty patients were randomized and analyzed in an intent-to-treat fashion. Median day of transition was day 96 (withdrawal) and 68 (minimization). Patients in the CNI-withdrawal group (n = 23) had significantly higher eGFR at one yr compared to the CNI-minimization group (n = 17, 73 vs. 56 mL/min, p = 0.03), as well as a significantly larger increase in eGFR from baseline (12 vs. 5 mL/min, p = 0.03). There were no differences in infections, acute rejection, death, or graft loss. Both regimens were constrained by disproportionately high discontinuation rates despite modest toxicity profiles. In spite of considerable withdrawal rate across both study arms, African American kidney transplant recipients who underwent early transition to a sirolimus-based CNI-withdrawal regimen had significantly better graft function at one yr compared to those transitioned to a sirolimus-based CNI-minimization regimen. Clinicaltrials.gov identifier: NCT01005706.

Genomewide Association Study of Tacrolimus Concentrations in African American Kidney Transplant Recipients Identifies Multiple CYP3A5 Alleles

We previously reported that tacrolimus (TAC) trough blood concentrations for African American (AA) kidney allograft recipients were lower than those observed in white patients. Subtherapeutic TAC troughs may be associated with acute rejection (AR) and AR-associated allograft failure. This variation in TAC troughs is due, in part, to differences in the frequency of the cytochrome P450 CYP3A5*3 allele (rs776746, expresses nonfunctional enzyme) between white and AA recipients; however, even after accounting for this variant, variability in AA-associated troughs is significant. We conducted a genomewide association study of TAC troughs in AA kidney allograft recipients to search for additional genetic variation. We identified two additional CYP3A5 variants in AA recipients independently associated with TAC troughs: CYP3A5*6 (rs10264272) and CYP3A5*7 (rs41303343). All three variants and clinical factors account for 53.9% of the observed variance in troughs, with 19.8% of the variance coming from demographic and clinical factors including recipient age, glomerular filtration rate, anticytomegalovirus drug use, simultaneous pancreas-kidney transplant and antibody induction. There was no evidence of common genetic variants in AA recipients significantly influencing TAC troughs aside from the CYP3A gene. These results reveal that additional and possibly rare functional variants exist that account for the additional variation.

Impact of Maintenance Steroids versus Rapid Steroid Withdrawal in African-American Kidney Transplant Recipients: Comparison of Two Urban Centers.

BackgroundRapid steroid withdrawal (RSW) is used increasingly in kidney transplantation but long-term outcomes in African-American (AA) recipients are not well known. We compared 1 and 5 year transplant outcomes in a large cohort of AA patients who were maintained on continued steroid therapy (CST) to those who underwent RSW.MethodsPost-transplant courses of A as receiving kidney allografts from 2003–2011 at two urban transplant centers in Chicago were followed. Prior to outcome analysis, we used Inverse Probability of Treatment Weights (IPTW) to match the two groups on a set of baseline risk factors. Graft and patient survival, GFR at 1 and 5 years, incidence and type of rejection, incidence of post-transplant diabetes mellitus (PTDM), delayed graft function, CMV and BK viremia were compared.ResultsThere were 150 AA recipients in the CST analytic group and 157 in the RSW analytic group. Graft and patient survival was similar between the two groups. Rates of CMV viremia were higher in the RSW compared to the CST analytic group at 1 year. Biopsy-proven acute rejection and PTDM were similar between the RSW and CST groups.ConclusionsIn AA recipients, RSW has similar long-term outcomes to CST.

Genotype-guided tacrolimus dosing in African-American kidney transplant recipients.

Tacrolimus is dependent on CYP3A5 enzyme for metabolism. Expression of the CYP3A5 enzyme is controlled by several alleles including CYP3A5*1, CYP3A5*3, CYP3A5*6 and CYP3A5*7. African Americans (AA) have on average higher tacrolimus dose requirements than Caucasians; however, some have requirements similar to Caucasians. Studies in AA have primarily evaluated the CYP3A5*3 variant; however, there are common nonfunctional variants in AA (CYP3A5*6 and CYP3A5*7) which do not occur in Caucasians. These variants are associated with lower dose requirements and may explain why some AA are metabolically similar to Caucasians. We created a tacrolimus clearance model in 354 AA using a development and validation cohort. Time posttransplant, steroid and antiviral use, age, CYP3A5*1, *3, *6 and *7 alleles were significant towards clearance. This study is the first to develop an AA specific genotype-guided tacrolimus dosing model to personalize therapy.

Patient-Centered mHealth Living Donor Transplant Education Program for African Americans: Development and Analysis.

BackgroundThere is a critical need to expand the pool of available kidneys for African Americans who are on the transplant wait-list due to the disproportionally lower availability of deceased donor kidneys compared with other races/ethnic groups. Encouraging living donation is one method to fill this need. Incorporating mHealth strategies may be a way to deliver educational and supportive services to African American transplant-eligible patients and improve reach to those living in remote areas or unable to attend traditional group-session-based programs. Before program development, it is essential to perform formative research with target populations to determine acceptability and cultivate a patient-centered and culturally relevant approach to be used for program development.ObjectiveThe objectives of this study were to investigate African American kidney transplant recipients’ and kidney donors’/potential donors’ attitudes and perceptions toward mobile technology and its viability in an mHealth program aimed at educating patients about the process of living kidney donation.MethodsUsing frameworks from the technology acceptance model and self-determination theory, 9 focus groups (n=57) were administered to African Americans at a southeastern medical center, which included deceased/living donor kidney recipients and living donors/potential donors. After a demonstration of a tablet-based video education session and explanation of a group-based videoconferencing session, focus groups examined members’ perceptions about how educational messages should be presented on topics pertaining to the process of living kidney donation and the transplantation. Questionnaires were administered on technology use and perceptions of the potential program communication platform. Transcripts were coded and themes were examined using NVivo 10 software.ResultsQualitative findings found 5 major themes common among all participants. These included the following: (1) strong support for mobile technology use; (2) different media formats were preferred; (3) willingness to engage in video chats, but face-to-face interaction sometimes preferred; (4) media needs to be user friendly; (5) high prevalence of technology access. Our results show that recipients were willing to spend more time on education than the donors group, they wanted to build conversation skills to approach others, and preferred getting information from many sources, whereas the donor group wanted to hear from other living donors. The questionnaires revealed 85% or more of the sample scored 4+ on a 5-point Likert scale, which indicates high degree of interest to use the proposed program, belief that other mHealth technologies would help with adherence to medical regimens, and doctors would make regimen adjustments quicker. In addition, high utilization of mobile technology was reported; 71.9% of the participants had a mobile phone and 43.9% had a tablet.ConclusionsOur study supports the use of an mHealth education platform for African Americans to learn about living donation. However, potential recipients and potential donors have differing needs, and therefore, programs should be tailored to each target audience.