Serum erythropoietin level and mortality in kidney transplant recipients

Anemia after kidney transplantation: Does its basis differ from anemia in chronic kidney disease?

BACKGROUND

Although similar factors play a role in both PTA and anemia in patients with CKD, additional risk factors exist in the pathogenesis of PTA. The present study aimed at comparing anemia and inflammation-related parameters between RTx recipients and CKD patients and elucidating the risk factors of PTA.

METHODS

This single-centered, cross-sectional study consisted of 68 participants: 48 were in the RTx group and 20 were in the CKD group. The CKD patients were comparable to the RTx recipients in terms of age, gender, and eGFR. Serum levels of EPO, hepcidin, and IL-6 were measured by enzyme-linked immunosorbent assays. The ratio of EPO/Hb was calculated to estimate endogenous EPO resistance.

RESULTS

The prevalence of anemia was 46% in the RTx group and 30% in the CKD group (P = .23). RTx recipients had significantly lower Hb (P = .04), higher EPO (P < .001), and ferritin levels (P = .001), and higher EPO/Hb ratios (P < .001); however, CKD patients showed a higher frequency of absolute iron deficiency (P = .008). Neither hepcidin nor IL-6 levels differed between the two groups. Hb level of RTx recipients was correlated with only eGFR (r = .437, P = .002) but not with any of the transplantation-related factors, while Fe level was the only parameter to be correlated with Hb level of CKD patients (r = .622, P = .01).

CONCLUSION

In the present study comparing GFR-matched RTx and CKD patients, lower GFR level appears to be the factor most strongly associated with anemia, and endogenous EPO resistance is among the contributing factors to PTA.

Erythropoietin, Fibroblast Growth Factor 23, and Death After Kidney Transplantation

Elevated levels of erythropoietin (EPO) are associated with an increased risk of death in renal transplant recipients (RTRs), but the underlying mechanisms remain unclear. Emerging data suggest that EPO stimulates production of the phosphaturic hormone fibroblast growth factor 23 (FGF23), another strong risk factor for death in RTRs. We hypothesized that the hitherto unexplained association between EPO levels and adverse outcomes may be attributable to increased levels of FGF23. We included 579 RTRs (age 51 ± 12 years, 55% males) from the TransplantLines Insulin Resistance and Inflammation Cohort study (NCT03272854). During a follow-up of 7.0 years, 121 RTRs died, of which 62 were due to cardiovascular cause. In multivariable Cox regression analysis, EPO was independently associated with all-cause (HR, 1.66; 95% CI 1.16–2.36; P = 0.005) and cardiovascular death (HR, 1.87; 95% CI 1.14–3.06; P = 0.01). However, the associations were abrogated following adjustment for FGF23 (HR, 1.28; 95% CI 0.87–1.88; P = 0.20, and HR, 1.45; 95% CI 0.84–2.48; P = 0.18, respectively). In subsequent mediation analysis, FGF23 mediated 72% and 50% of the association between EPO and all-cause and cardiovascular death, respectively. Our results underline the strong relationship between EPO and FGF23 physiology, and provide a potential mechanism underlying the relationship between increased EPO levels and adverse outcomes in RTRs.

The effect of maintaining high hemoglobin levels on long-term kidney function in kidney transplant recipients: a randomized controlled trial

Background

Posttransplant anemia may be a major determinant of chronic allograft nephropathy. However, the impact of correcting anemia on graft function remains controversial.

Methods

A 3-year follow-up of an open-label, multicenter, randomized controlled trial involving kidney transplantation recipients examined whether sustained maintenance of target hemoglobin (Hb) concentrations at a high level (12.5–13.5 g/dL, n = 64) with either darbepoetin alfa or epoetin beta pegol would slow the graft function decline rate as the primary efficacy endpoint, compared with maintenance of a low Hb concentration (10.5–11.5 g/dL, n = 63).

Results

The mean blood pressures in the two groups were well controlled throughout the study. In the high Hb group, mean Hb concentrations increased to >12 g/dL at 3 months, reaching the target range at 18 months. At the end of this study (36 months), the mean Hb concentration was 12.8 ± 0.7 g/dL in the high Hb group and 11.5 ± 1.2 g/dL in the low Hb group. The decline rate of the estimated glomerular filtration (eGFR) rate was considerably greater in the low Hb group (ΔeGFR, −5.1 ± 9.5 mL/min/1.73 m²) than in the high Hb group (−1.0 ± 8.4 mL/min/1.73 m²) (P = 0.02). Of note, only a few high Hb patients developed cardiovascular events and returned to hemodialysis, but the low Hb patients did not.

Conclusion

This prospective study suggests that correcting anemia to the target Hb level range (12.5–13.5 g/dL) slows renal function deterioration by >3 years in the chronic phase of allograft nephropathy.

Low erythropoietin levels predict faster renal function decline in diabetic patients with anemia: a prospective cohort study

Elevated erythropoietin (EPO) levels have been reported to predict poor survival in various populations including diabetic patients. However, data regarding its impact on renal outcomes are scarce. We conducted a single-center, prospective cohort study of 339 type 2 diabetic patients with anemia. The primary outcome was the estimated glomerular filtration rate (eGFR) slope for two years. We performed multiple linear regression and restricted cubic spline analyses to assess the association of serum EPO levels with the renal outcome. Chronic kidney disease (CKD) was defined as eGFR <60 mL/min/1.73 m2 or urine albumin-to-creatinine ratio >30 mg/g creatinine. Median baseline EPO and eGFR level were 14.4 IU/L and 53 mL/min/1.73 m², respectively. Inappropriately low EPO levels were observed in 73% of anemic patients and 59% of anemic patients even without CKD, suggesting that EPO deficiency precedes the onset of CKD in diabetes mellitus. Multivariable analysis revealed that iron status and hemoglobin levels were major determinants of EPO levels. Median eGFR slope was −1.3 mL/min/1.73 m²/year. We found that low EPO levels, but not low hemoglobin levels, were associated with a faster decline in eGFR, independent of clinically relevant factors. The eGFR decline was steeper, particularly when the EPO level was below the upper limit of normal. Lower EPO concentrations were associated with rapid eGFR decline, especially in patients with iron deficiency (P for interaction = 0.01). Relative EPO deficiency should be considered as a culprit in anemia of unknown etiology in diabetic patients, even those without CKD. Low EPO levels, especially when accompanied by poor iron status, are predictive of rapid loss of renal function.

Iron deficiency, elevated erythropoietin, fibroblast growth factor 23, and mortality in the general population of the Netherlands: A cohort study

BACKGROUND

Emerging data in chronic kidney disease (CKD) patients suggest that iron deficiency and higher circulating levels of erythropoietin (EPO) stimulate the expression and concomitant cleavage of the osteocyte-derived, phosphate-regulating hormone fibroblast growth factor 23 (FGF23), a risk factor for premature mortality. To date, clinical implications of iron deficiency and high EPO levels in the general population, and the potential downstream role of FGF23, are unclear. Therefore, we aimed to determine the associations between iron deficiency and higher EPO levels with mortality, and the potential mediating role of FGF23, in a cohort of community-dwelling subjects.

METHODS AND FINDINGS

We analyzed 6,544 community-dwelling subjects (age 53 ± 12 years; 50% males) who participated in the Prevention of Renal and Vascular End-Stage Disease (PREVEND) study-a prospective population-based cohort study, of which we used the second survey (2001-2003)-and follow-up was performed for a median of 8 years. We measured circulating parameters of iron status, EPO levels, and plasma total FGF23 levels. Our primary outcome was all-cause mortality. In multivariable linear regression analyses, ferritin (ß = -0.43), transferrin saturation (TSAT) (ß = -0.17), hepcidin (ß = -0.36), soluble transferrin receptor (sTfR; ß = 0.33), and EPO (ß = 0.28) were associated with FGF23 level, independent of potential confounders. During median (interquartile range [IQR]) follow-up of 8.2 (7.7-8.8) years, 379 (6%) subjects died. In multivariable Cox regression analyses, lower levels of TSAT (hazard ratio [HR] per 1 standard deviation [SD], 0.84; 95% confidence interval [CI], 0.75-0.95; P = 0.004) and higher levels of sTfR (HR, 1.15; 95% CI 1.03-1.28; P = 0.01), EPO (HR, 1.17; 95% CI 1.05-1.29; P = 0.004), and FGF23 (HR, 1.20; 95% CI 1.10-1.32; P < 0.001) were each significantly associated with an increased risk of death, independent of potential confounders. Adjustment for FGF23 levels markedly attenuated the associations of TSAT (HR, 0.89; 95% CI 0.78-1.01; P = 0.06), sTfR (HR, 1.08; 95% CI 0.96-1.20; P = 0.19), and EPO (HR, 1.10; 95% CI 0.99-1.22; P = 0.08) with mortality. FGF23 remained associated with mortality (HR, 1.15; 95% CI 1.04-1.27; P = 0.008) after adjustment for TSAT, sTfR, and EPO levels. Mediation analysis indicated that FGF23 explained 31% of the association between TSAT and mortality; similarly, FGF23 explained 32% of the association between sTfR and mortality and 48% of the association between EPO and mortality (indirect effect P < 0.05 for all analyses). The main limitations of this study were the observational study design and the absence of data on intact FGF23 (iFGF23), precluding us from discerning whether the current results are attributable to an increase in iFGF23 or in C-terminal FGF23 fragments.

CONCLUSIONS AND RELEVANCE

In this study, we found that functional iron deficiency and higher EPO levels were each associated with an increased risk of death in the general population. Our findings suggest that FGF23 could be involved in the association between functional iron deficiency and increased EPO levels and death. Investigation of strategies aimed at correcting iron deficiency and reducing FGF23 levels is warranted.

Development and future deployment of a 5 years allograft survival model for kidney transplantation

AIM

Identifying kidney transplant patients at highest risk for graft loss prior to loss may allow for effective interventions to improve 5 years survival.

METHODS

We performed a 10 years retrospective cohort study of adult kidney transplant recipients (n = 1747). We acquired data from electronic health records, United Network of Organ Sharing, social determinants of health, natural language processing data extraction, and real-time capture of dynamically evolving clinical data obtained within 1 year of transplant; from which we developed a 5 years graft survival model.

RESULTS

Total of 1439 met eligibility; 265 (18.4%) of them experienced graft loss by 5 years. Graft loss patients were characterized by: older age, being African-American, diabetic, unemployed, smokers, having marginal donor kidneys and cardiovascular comorbidities. Predictive dynamic variables included: low mean blood pressure, higher pulse pressures, higher heart rate, anaemia, lower estimated glomerular filtration rate peak, increased tacrolimus variability, rejection and readmissions. This Big Data analysis generated a 5 years graft loss model with an 82% predictive capacity, versus 66% using baseline United Network of Organ Sharing data alone.

CONCLUSION

Our analysis yielded a 5 years graft loss model demonstrating superior predictive capacity compared with United Network of Organ Sharing data alone, allowing post-transplant individualized risk-assessed care prior to transitioning back to community care.

Low 1,25-dihydroxyvitamin D level is associated with erythropoietin deficiency and endogenous erythropoietin resistance in patients with chronic kidney disease

PURPOSE

Erythropoietin (EPO) deficiency and resistance to endogenous EPO is an important pathophysiological feature in anemia of chronic kidney disease (CKD). Low 1,25 dihydroxyvitamin D [1,25(OH)₂D] level is known to contribute to anemia of CKD. We aimed to investigate the associations between serum 1,25(OH)₂D and anemia, EPO deficiency, and endogenous EPO resistance in patients with CKD.

METHODS

This study included 409 patients with CKD [glomerular filtration rate (GFR) < 60 ml/min/1.73 m²] who were not on dialysis therapy. Patients on exogenous EPO therapy and patients with iron deficiencies were excluded. Endogenous EPO resistance was assessed by calculating the ratio of endogenous EPO to hemoglobin (Hb) (endogenous EPO/Hb ratio). The associations of Hb level, endogenous EPO level, and the endogenous EPO/Hb ratio with clinical and laboratory variables were investigated by univariate and multivariate analyses.

RESULTS

In univariate analysis, serum 1,25(OH)₂D level was correlated with the Hb level, endogenous EPO level, and the endogenous EPO/Hb ratio. Multiple regression analysis revealed that the serum 1,25(OH)₂D level remained significantly associated with the Hb level (β = 0.532, P < 0.001), endogenous EPO level (β = 0.149, P = 0.010), and the endogenous EPO/Hb ratio (β = - 0.187, P = 0.002), even after adjusting for other confounding factors, including the levels of parathyroid hormone and the inflammatory marker C-reactive protein.

CONCLUSION

The serum 1,25(OH)₂D level exhibited significant associations with anemia, EPO deficiency, and endogenous EPO resistance in CKD patients. These associations were independent of secondary hyperparathyroidism and inflammation status.

Anemia and markers of erythropoiesis in pediatric kidney transplant recipients compared to children with chronic renal failure

PTA and anemia of CKD share a similar pathogenesis. However, PTA may be disproportionate to the reduction in the GFR. Data relating to the mechanism of PTA are scarce. We evaluated the erythropoiesis parameters in pediatric kidney recipients compared to children with CKD. A total of 100 patients (54 post-kidney TX, 46 with CKD) were enrolled in the single-center cohort study. GFR was found to be significantly lower in the CKD group (49.7±22.4 vs 72.9±28.5 mL/min/1.73 m², P<.001); anemia was significantly more common in the TX patients (52% vs 41.3%, P<.001). Iron transferrin saturation and serum ferritin levels were lower in the CKD patients. In both groups, hemoglobin Z scores significantly correlated with GFR (R=.31, P=.07). This correlation was more prominent in the CKD group (R=.43, P=.008) compared to the TX group (R=.31, P=.04). Anemia was significantly more common in the TX patients than in the CKD patients despite a better GFR. The higher prevalence of anemia in the TX group could not be explained by an iron deficiency or reduced EPO production. We speculate that immunosuppressive therapy together with resistance to EPO may play a role in the pathogenesis of post-transplantation anemia.

Association Between Serum Leptin Level and Mortality in Kidney Transplant Recipients

OBJECTIVE

Leptin is a hormone made by adipocytes and associated with hypertension, inflammation, and coronary artery disease. Low serum leptin level was associated with higher risk of death in patients with advanced chronic kidney disease. Little is known about the association of serum leptin with outcomes in kidney transplant recipients.

DESIGN

Prospective prevalent cohort.

SETTING AND SUBJECT

We collected sociodemographic and clinical parameters, medical and transplant history, and laboratory data of 979 prevalent kidney transplant recipients. Associations between serum leptin level and death with a functioning graft, all-cause death, and death-censored graft loss over a 6-year follow-up period were examined in survival models.

RESULTS

Serum leptin levels showed moderate negative correlation with eGFR (R = -0.21, P < .001) and positive correlations with BMI (R = 0.48, P < .001) and C-reactive protein (R = 0.20, P < .001). Each 10 ng/mL higher serum leptin level was associated with 7% lower risk of death with functioning graft (hazard ratio [HR] (95% confidence interval [CI]), 0.93 (0.87-0.99)), and this association persisted after adjustment for confounders: HR (95% CI), 0.90 (0.82-0.99). Similar associations were found with all-cause death as outcome. The association between serum leptin level and risk of graft loss was nonlinear, and only low serum leptin level was associated with higher risk of graft loss.

CONCLUSIONS

In prevalent kidney transplant recipients, lower serum leptin was an independent predictor of death.

Adipocytokines in renal transplant recipients

In the last two decades, perceptions about the role of body fat have changed. Adipocytes modulate endocrine and immune homeostasis by synthesizing hundreds of hormones, known as adipocytokines. Many studies have been investigating the influences and effects of these adipocytokines and suggest that they are modulated by the nutritional and immunologic milieu. Kidney transplant recipients (KTRs) are a unique and relevant population in which the function of adipocytokines can be examined, given their altered nutritional and immune status and subsequent dysregulation of adipocytokine metabolism. In this review, we summarize the recent findings about four specific adipocytokines and their respective roles in KTRs. We decided to evaluate the most widely described adipocytokines, including leptin, adiponectin, visfatin and resistin. Increasing evidence suggests that these adipocytokines may lead to cardiovascular events and metabolic changes in the general population and may also increase mortality and graft loss rate in KTRs. In addition, we present findings on the interrelationship between serum adipocytokine levels and nutritional and immunologic status, and mechanisms by which adipocytokines modulate morbidity and outcomes in KTRs.

Association between serum resistin level and outcomes in kidney transplant recipients

Resistin is an adipocytokine that is associated with inflammation, coronary artery disease, and other types of cardiovascular disease among patients with normal kidney function. However, little is known about the association of resistin with outcomes in kidney transplant recipients. We collected socio-demographic and clinical parameters, medical and transplant history, and laboratory data from 988 prevalent kidney transplant recipients enrolled in the Malnutrition-Inflammation in Transplant-Hungary Study (MINIT-HU study). Serum resistin levels were measured at baseline. Associations between serum resistin level and death with a functioning graft over a 6-year follow-up period were examined in unadjusted and adjusted models. The mean±SD age of the study population was 51 ± 13 years, among whom 57% were men and 21% were diabetics. Median serum resistin concentrations were significantly higher in patients who died with a functioning graft as compared to those who did not die during the follow-up period (median [IQR]: 22[15-26] vs. 19[14-22] ng/ml, respectively; P < 0.001). Higher serum resistin level was associated with higher mortality risk in both unadjusted and fully adjusted models: HRs (95% CI): 1.33(1.16-1.54) and 1.21(1.01-1.46), respectively. In prevalent kidney transplant recipients, serum resistin was an independent predictor of death with a functioning graft.

Diagnostic validation and prognostic significance of the Malnutrition-Inflammation Score in nondialyzed chronic kidney disease patients

BACKGROUND

Malnutrition and inflammation are highly prevalent and intimately linked conditions in chronic kidney disease (CKD) patients that lead to a state of protein-energy wasting (PEW), the severity of which can be assessed by the Malnutrition-Inflammation Score (MIS). Here, we applied MIS and validated, for the first time, its ability to grade PEW and predict mortality in nondialyzed CKD patients.

METHODS

We cross-sectionally evaluated 300 CKD stages 3-5 patients [median age 61 (53-68) years; estimated glomerular filtration rate 18 (12-27) mL/min/1.73 m(2); 63% men] referred for the first time to our center. Patients were followed during a median 30 (18-37) months for all-cause mortality.

RESULTS

A worsening in MIS scale was associated with inflammatory biomarkers increase (i.e. alpha-1 acid glycoprotein, fibrinogen, ferritin and C-reactive protein) as well as a progressive deterioration in various MIS-independent indicators of nutritional status based on anthropometrics, dynamometry, urea kinetics and bioelectric impedance analysis. A structural equation model with two latent variables (assessing simultaneously malnutrition and inflammation factors) demonstrated good fit to the observed data. During a follow-up, 71 deaths were recorded; patients with higher MIS were at increased mortality risk in both crude and adjusted Cox models.

CONCLUSIONS

MIS appears to be a useful tool to assess PEW in nondialyzed CKD patients. In addition, MIS identified patients at increased mortality risk.

Blood disorders after kidney transplantation

Post transplant anemia (PTA) is a common issue in kidney transplant recipients. Most importantly it is associated with an impaired allograft function. Other important factors associated with PTA are immunosuppressive drugs (MPA, AZA and SRL), iron deficiency, infections (Parvo B19), older donor age, rejection episodes, an increased inflammatory state, and erythropoietin hyporesponsiveness. As there are no adequately powered RCTs in the kidney transplant population on anemia treatment with ESA, we have to rely on what we know from the large RCTs in the CKD population. The recently published KDIGO guidelines do not recommend treatment with ESA if Hb is >10 g/dl. Repletion of iron stores is emphasized. Post transplant leukopenia (PTL) and thrombocytopenia (PTT) are frequent complications especially in the first six months after kidney transplantation. Myelosuppression caused by immunosuppressive agents (MPA, AZA, SRL, rATG), antimicrobial drugs (VGCV), and CMV infection is the predominant cause. There are no widely accepted guidelines on treatment strategies, but most often dose reduction or discontinuation of causative medication is done. Most clinicians tend to decrease MPA dose, but this is eventually associated with an increase in acute rejection episodes. VGCV dose reduction (preemptive treatment instead of CMV prophylaxis) may be a successful strategy. In severe cases G-CSF treatment is an important management option and seems to be safe.

Renal function is independently associated with red cell distribution width in kidney transplant recipients: a potential new auxiliary parameter for the clinical evaluation of patients with chronic kidney disease

Red cell distribution width (RDW), a measure of heterogeneity in the size of circulating erythrocytes, reportedly predicts mortality. Similarly to RDW, impaired renal function is also associated with inflammation and protein-energy wasting. This study assessed if renal function is associated with RDW independent of relevant confounders in stable kidney transplant recipients. We examined the association between RDW and estimated glomerular filtration rate (eGFR) in a cohort of 723 prevalent kidney transplanted recipients who were not receiving erythropoietin-stimulating agents. Associations were examined in regression models adjusted for age, sex, comorbidity, blood haemoglobin, iron indices, markers of nutritional status and inflammation, markers of bone and mineral metabolism and the use of immune suppressants. Lower eGFR was significantly associated with higher RDW (r = -0·382, P < 0·001). This association remained highly significant even after multivariate adjustments where 10 ml/min decrease in the eGFR was significantly associated with an increase of the RDW values (B10 ml/min decrease  =  0·078; 95% confidence interval: 0·044-0·111). The results were consistent in subgroups of patients with different levels of haemoglobin, chronic kidney disease status and various markers of inflammation and iron status. Lower eGFR is associated with higher RDW, independent of comorbidity, iron deficiency, inflammation and nutritional status in kidney transplant recipients.

Association of pre-transplant erythropoiesis-stimulating agent responsiveness with post-transplant outcomes

BACKGROUND

The role of pre-transplant erythropoiesis-stimulating agent (ESA) responsiveness in affecting post-transplant outcomes is not clear.

METHODS

Linking the 5-year patient data of a large dialysis organization to the 'Scientific Registry of Transplant Recipients', we identified 8795 hemodialyzed patients who underwent first kidney transplantation. Mortality or graft failure, delayed graft function (DGF) and acute rejection risks were estimated by Cox regression [hazard ratio (HR)] and logistic regression, respectively.

RESULTS

Patients were 48 ± 14 years old and included 38% women and 36% diabetics. Compared to renal allograft recipients who were in the first quartile of pre-transplant ESA responsiveness index (ERI), i.e. ESA dose divided by hemoglobin and weight, recipients in second, third and fourth quartiles had higher adjusted graft-censored death HR (and 95% confidence intervals) of 1.7 (1.0-2.7), 1.8 (1.1-2.9) and 2.3 (1.4-3.9) and higher death-censored graft failure HR of 1.6 (1.0-2.5), 2.0 (1.2-3.1) and 1.6 (0.9-2.6), respectively. No significant association between pre-transplant ERI and post-transplant DGF or acute rejection was detected.

CONCLUSIONS

Higher pre-transplant ERI during the hemodialysis treatment period was associated with worse post-transplant long-term outcomes including increased all-cause death and higher risk of graft failure.

Associations of pre-transplant anemia management with post-transplant delayed graft function in kidney transplant recipients

BACKGROUND

Delayed graft function (DGF) complicates kidney allograft outcomes in the immediate post-transplantation period. We hypothesized that in hemodialysis patients more severe anemia, iron deficiency, the requirement for higher doses of erythropoietin-stimulating agents (ESA), or blood transfusions prior to transplantation are associated with higher risk of DGF.

METHODS

Linking five-yr hemodialysis patient data of a large dialysis organization to the Scientific Registry of Transplant Recipients, we identified 11 836 hemodialysis patients. Using logistic regression analyses we examined the association between pre-transplant parameters and post-transplant DGF.

RESULTS

Patients were 49 ± 14 (mean ± SD) yr old and included 38% women, 27% blacks, and 26% diabetics. After adjusting for relevant covariates, pre-transplant blood transfusion was associated with 33% higher DGF risk (odds ratio [OR] = 1.33; 95% confidence interval [CI]: 1.19-1.48); and each 5000 U/wk increase of pre-transplant ESA dose with 5% higher DGF (OR = 1.05; 95% CI: 1.02-1.09). Compared to pre-transplant blood hemoglobin of 12-12.99 g/dL, there was 25% higher risk of DGF with blood hemoglobin 10-10.99 g/dL (OR = 1.25; 95% CI: 1.01-1.55), whereas blood hemoglobin ≥13 g/dL exhibited 15% higher risk of DGF (OR = 1.15; 95% CI: 0.98-1.34).

CONCLUSIONS

Pre-transplant blood transfusion, higher ESA dose, and either high or low blood hemoglobin but not iron markers are associated with higher risk of DGF.