Renal Function Variability: An Independent Risk Factor for Graft Loss and Death following Kidney Transplantation

Deceased donor urinary Dickkopf-3 associates with future allograft function following kidney transplantation

Predicting future kidney allograft function is challenging. Novel biomarkers, such as urinary Dickkopf-3 (uDKK3), may help guide donor selection and improve allograft outcomes. In this prospective multicenter pilot trial, we investigated whether donor uDKK3 reflects organ quality and is associated with future allograft function. We measured uDKK3/crea ratios (uDKK3/crea) from 95 deceased and 46 living kidney donors. Prenephrectomy uDKK3/crea levels were 100× higher in deceased than in living donors (9888 pg/mg vs 113 pg/mg; P < .001). Among deceased donor transplantations, recipients were stratified by their corresponding uDKK3/crea donor levels ranging below (group A, n = 68) or above (group B, n = 65) median. The primary end point of best estimated glomerular filtration rate (eGFR) within the first 3 months after kidney transplantation was superior in group A (56.3 mL/min/1.73 m2) than that in group B (44.2 mL/min/1.73 m2; P = .0139). Second, the composite clinical end point consisting of death, allograft failure or eGFR decline >50% occurred less frequent in group A. By mixed linear regression modeling, donor uDKK3/crea remained an independent predictor of eGFR after transplantation, with a slope of -4.282 mL/min/1.73 m2 per logarithmic increase in donor uDKK3/crea. In summary, uDKK3 may serve as a noninvasive, donor-dependent biomarker for assessing organ quality and future allograft function.

Comparison of Clinical Outcomes Between Two Types of Dipeptidyl Peptidase-4 Inhibitors in Posttransplant Diabetes Mellitus in Kidney Transplantation Recipients: A Nationwide Population-Based Cohort Study in Korea

BACKGROUND

Dipeptidyl peptidase-4 inhibitors (DPP-4i) are antidiabetic drugs known for their minimal side effects and limited drug interaction witih immunosuppressants, making them suitable for patients with diabetes and kidney transplant recipients. However, there is limited real-world information regarding the use of DPP-4 inhibitors in patients with post transplant diabetes mellitus (PTDM).

METHOD

We performed a retrospective observational cohort study of 13,828 kidney transplant recipients form Janary 1, 2002, through December 21, 2018, using the Korean National Health Information Database. We extracted PTDM patients, and divided the patients into 2 groups baased on whether they received DPP4-inhibitor which needs dose adjustement (group A) or not (Group B) according to estimaged glomerular filtration rate.

RESULTS

Out of 3154 patients who developed PTDM after transplantation, 738 patients prescribed DPP-4 inhibitors. Among these, 490 patients prescribed Group B DPP-4 inhibitors and 238 patients prescribed Group A DPP-4 inhibitors. Multivariate-adjusted Cox regression analysis showed that compared Group B, Group A DPP-4 inhibitors was associated with higher incidence rate of genital tract infection (hazard ratio (HR) 1.87, 95% Confidence Interval (CI) 1.18-2.99), and emergency department visit (HR 3.12, 95% CI 1.89-5.16). However, there was no significantly difference in death (any cause), admission, graft failure, infection, or hypoglycemia between the 2 groups.

CONCLUSIONS

In patients with PTDM, some kinds of DPP-4 inhibitors, which need dose adjustment according to renal function, were associated with an increased rate of emergency department visit and genital tract infection.

Costs in the Year Following Deceased Donor Kidney Transplantation: Relationships With Renal Function and Graft Failure

Relationships between renal function and medical costs for deceased donor kidney transplant recipients are not fully quantified post-transplant. We describe these relationships with renal function measured by estimated glomerular filtration rate (eGFR) and graft failure. The United States Renal Data System identified adults receiving single-organ deceased donor kidneys 2012–2015. Inpatient, outpatient, other facility costs and eGFRs at discharge, 6 and 12 months were included. A time-history of costs was constructed for graft failures and monthly costs in the first year post-transplant were compared to those without failure. The cohort of 24,021 deceased donor recipients had a 2.4% graft failure rate in the first year. Total medical costs exhibit strong trends with eGFR. Recipients with 6-month eGFRs of 30–59 ml/min/1.73m² have total costs 48% lower than those <30 ml/min/1.73m². For recipients with graft failure monthly costs begin to rise 3–4 months prior to failure, with incremental costs of over $38,000 during the month of failure. Mean annual total incremental costs of graft failure are over $150,000. Total costs post-transplant are strongly correlated with eGFR. Graft failure in the first year is an expensive, months-long process. Further reductions in early graft failures could yield significant human and economic benefits.

Clinical Events and Renal Function in the First Year Predict Long-Term Kidney Transplant Survival

BACKGROUND

Estimated glomerular filtration rate (eGFR) at 1 year post transplantation has been shown to be a strong predictor of long-term graft survival. However, intercurrent events (ICEs) may affect the relationship between eGFR and failure risk.

METHODS

The OPTN and USRDS databases on single-organ kidney transplant recipients from 2012 to 2016 were linked. Competing risk regressions estimated adjusted subhazard ratios (SHRs) of 12-month eGFR on long-term graft failure, considering all-cause mortality as the competing risk, for deceased donor (DD) and living donor (LD) recipients. Additional predictors included recipient, donor, and transplant characteristics. ICEs examined were acute rejection, cardiovascular events, and infections.

RESULTS

Cohorts comprised 25,131 DD recipients and 7471 LD recipients. SHRs for graft failure increased rapidly as 12-month eGFR values decreased from the reference 60 ml/min per 1.73 m². At an eGFR of 20 ml/min per 1.73 m², SHRs were 13-15 for DD recipients and 12-13 for LD recipients; at an eGFR of 30 ml/min per 1.73 m², SHRs were 5.0-5.7 and 5.0-5.5, respectively. Among first-year ICEs, acute rejection was a significant predictor of long-term graft failure in both DD (SHR=1.63, P<0.001) and LD (SHR=1.51, P=0.006) recipients; cardiovascular events were significant in DD (SHR=1.24, P<0.001), whereas non-CMV infections were significant in the LD cohort (SHR=1.32, P=0.03). Adjustment for ICEs did not significantly reduce the association of eGFR with graft failure.

CONCLUSIONS

Twelve-month eGFR is a strong predictor of long-term graft failure after accounting for clinical events occurring from discharge to 1 year. These findings may improve patient management and clinical evaluation of novel interventions.

Graft Function Variability and Slope and Kidney Transplantation Outcomes

Introduction

It is critical to identify kidney transplant recipients (KTRs) at higher risk for adverse outcomes, to focus on monitoring and interventions to improve outcomes. We examined the associations between graft function variability and long-term outcomes in KTRs in an observational study.

Methods

We identified 2919 KTRs in the Wisconsin Allograft Recipient Database (WisARD) who had a functioning allograft 2 years posttransplantation and at least 3 outpatient measurements of estimated glomerular filtration rate (eGFR) from 1 to 2 years posttransplantation. Graft function slope was calculated from a linear regression of eGFR, and variability was defined as the coefficient of variation around this regression line. Associations of eGFR variability and slope with death, graft failure, cardiovascular events, and acute rejection were estimated.

Results

Compared to the lowest quartile, the highest quartile of eGFR variability was associated with a higher risk of death (adjusted hazard ratio [HR] = 1.85; 95% CI = 1.23−2.76), but not with a higher risk of graft failure (subhazard ratio = 1.16; 95% CI = 0.85−1.58), independent of eGFR and slope of eGFR. Greater eGFR variability was associated with higher risk of cardiovascular- and infection-related death and cardiovascular events but not malignancy-related death or allograft rejection. Including variability of eGFR significantly improved prediction of mortality but not prediction of graft failure.

Conclusion

Variability of eGFR is independently associated with risk of death, especially cardiovascular disease−related death and cardiovascular events, but not graft failure. Variability of eGFR may help identify KTRs at higher risk for death and cardiovascular events.

Development and validation of routine clinical laboratory data derived marker-based nomograms for the prediction of 5-year graft survival in kidney transplant recipients

Background: To develop and validate predictive nomograms for 5-year graft survival in kidney transplant recipients (KTRs) with easily-available laboratory data derived markers and clinical variables within the first year post-transplant.

Methods: The clinical and routine laboratory data from within the first year post-transplant of 1289 KTRs was collected to generate candidate predictors. Univariate and multivariate Cox analyses and LASSO were conducted to select final predictors. X-tile analysis was applied to identify optimal cutoff values to transform potential continuous factors into category variables and stratify patients. C-index, calibration curve, dynamic time-dependent AUC, decision curve analysis, and Kaplan-Meier curves were used to evaluate models’ predictive accuracy and clinical utility.

Results: Two predictive nomograms were constructed by using 0–6- and 0–12- month laboratory data, and showed good predictive performance with C-indexes of 0.78 and 0.85, respectively, in the training cohort. Calibration curves showed that the prediction probabilities of 5-year graft survival were in concordance with actual observations. Additionally, KTRs could be successfully stratified into three risk groups by nomograms.

Conclusions: These predictive nomograms combining demographic and 0–6- or 0–12- month markers derived from post-transplant laboratory data could serve as useful tools for early identification of 5-year graft survival probability in individual KTRs.

Estimated GFR Variability and Risk of Cardiovascular Events and Mortality in SPRINT (Systolic Blood Pressure Intervention Trial)

RATIONALE AND OBJECTIVE

Although low estimated glomerular filtration rate (eGFR) is associated with cardiovascular disease (CVD) events and mortality, the clinical significance of variability in eGFR over time is uncertain. This study aimed to evaluate the associations between variability in eGFR and the risk of CVD events and all-cause mortality.

STUDY DESIGN

Longitudinal analysis of clinical trial participants.

SETTINGS AND PARTICIPANTS

7,520 Systolic Blood Pressure Intervention Trial (SPRINT) participants ≥50 year of age with 1 or more CVD risk factors.

PREDICTORS

eGFR variability, estimated by the coefficient of variation of eGFR assessments at the 6th, 12th, and 18-month study visits.

OUTCOMES

The SPRINT primary CVD composite outcome (myocardial infarction, acute coronary syndrome, stroke, heart failure, or CVD death) and all-cause mortality from month 18 to the end of follow-up.

ANALYTICAL APPROACH

Cox models were used to evaluate associations between eGFR variability and CVD outcomes and all-cause mortality. Models were adjusted for demographics, randomization arm, CVD risk factors, albuminuria, and eGFR at month 18.

RESULTS

Mean age was 68 ± 9 years; 65% were men; and 58% were White. The mean eGFR was 73 ± 21 (SD) mL/min/1.73 m² at 6 months. There were 370 CVD events and 154 deaths during a median follow-up of 2.4 years. Greater eGFR variability was associated with higher risk for all-cause mortality (hazard ratio [HR] per 1 SD greater variability, 1.29; 95% CI, 1.14-1.45) but not CVD events (HR, 1.05; 95% CI, 0.95-1.16) after adjusting for albuminuria, eGFR, and other CVD risk factors. Associations were similar when stratified by treatment arm and by baseline CKD status, when accounting for concurrent systolic blood pressure changes, use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, and diuretic medications during follow up.

LIMITATIONS

Persons with diabetes and proteinuria > 1 g/d were excluded.

CONCLUSIONS

In trial participants at high risk for CVD, greater eGFR variability was independently associated with all-cause mortality but not CVD events.

Relationship of Serum Bicarbonate Levels with 1-Year Graft Function in Kidney Transplant Recipients in Switzerland

BACKGROUND

Metabolic acidosis (MA) is common in kidney transplant recipients (KTRs). Several studies have shown that MA is involved in the progression of chronic kidney disease. However, it is unclear if there is also a relationship between serum bicarbonate and graft function after kidney transplantation (KTx). We hypothesized that low serum bicarbonate is associated with a lower estimated glomerular filtration rate (eGFR) 1 year after KTx.

METHODS

We performed a post hoc analysis of a single-center, open-label randomized trial in 90 KTRs and investigated the relationship of serum bicarbonate and graft function in the first year after KTx.

RESULTS

Prevalence of MA was high after KTx (63%) and decreased to 28% after 1 year. Bicarbonate (20.6 ± 3.0 to 22.7 ± 2.7 mmol/L) increased in the first year after transplantation whereas eGFR (53.4 ± 15.8 to 56.9 ± 18.5 mL/min/1.73 m2) did not change significantly. Higher serum bicarbonate (p = 0.029) was associated with higher eGFR in the first year after KTx.

CONCLUSION

Prevalence of MA is high in KTRs. In the first year after KTx, serum bicarbonate was positively correlated with eGFR, suggesting a potential role of MA in kidney graft function.