The greatly misunderstood erythropoietin resistance index and the case for a new responsiveness measure

The influencing factors of the erythropoietin resistance index and its association with all-cause mortality in maintenance hemodialysis patients

Anemia is a common complication of chronic kidney disease with major option treatment of erythropoiesis-stimulating agents (ESAs). This study aimed to investigate the influencing factors of erythropoietin resistance index (ERI) and its association with mortality in maintenance hemodialysis (MHD) patients. Patients enrolled from China Dialysis Outcomes and Practice Patterns Study (DOPPS) 5 were included. ERI was calculated as follows: ESA (IU/week)/weight (kg, post-dialysis)/hemoglobin level (g/dL). The Cox regression model was used to analyze the influencing factors on survival outcomes. Stepwise multivariate logistic regression was used to identify the related risk factors, and subgroup analyses were performed. A total of 1270 MHD subjects (687 males and 583 females) were included, with an average age of 60 (49.0, 71.0) years. All subjects were divided into two groups by the median ERI of 14.03. Multivariate logistic regression showed that dialysis vintage (OR 0.957, 95% CI: 0.929-0.986), white blood cells (OR 0.900, 95% CI: 0.844-0.960), high flux dialyzer use (OR 0.866, 95% CI: 0.755-0.993), body mass index (OR 0.860, 95% CI: 0.828-0.892), males (OR 0.708, 95% CI: 0.625-0.801), and albumin (OR 0.512, 95% CI: 0.389-0.673) had a negative association with high ERI baseline (all p < 0.05). There were 176 (13.9%) deaths in total including 89 cardiac/vascular deaths during follow-up. Cox regression analysis showed that ERI was positively associated with all-cause mortality, especially in some subgroups. ERI was associated with increased all-cause mortality in MHD patients, indicating the possibility of death prediction by ERI. Patients with high ERI warrant more attention.

Evaluation of hepcidin-25/erythroferrone ratio as a potential biomarker for iron utility and erythropoiesis responsiveness to erythropoiesis-stimulating therapy in comparison to immature erythrocyte/reticulocyte parameters in hemodialysis patients

BACKGROUND

Anemia-associated chronic kidney disease increases in more advanced stages with a subsequent acceleration in renal impairment progressing to end-stage renal disease. Although hepcidin and erythroferrone have been described as novel biomarkers of iron metabolism, there is still an area of ambiguity regarding iron utility in anemia-associated end-stage renal disease.

OBJECTIVES

This study aims to determine the correlations between erythropoietin, erythroferrone, and hepcidin-25 in hemodialysis, and to evaluate the clinical utility of the hepcidin-25/erythroferrone ratio as a biomarker of erythropoiesis-stimulating agent effectiveness compared to reticulocyte maturation parameters.

METHODS

Serum erythropoietin, erythroferrone, and hepcidin-25 levels in 35 dialysis-dependent patients on a maintenance dose of a short-acting erythropoiesis-stimulating agent were consequently assessed on Days 0, 5, and 7. The erythropoiesis activity was monitored by measuring the increment in reticulocyte maturation parameters.

RESULTS

Though the effectiveness of erythropoiesis in these patients was not associated with the hepcidin-25/erythroferrone ratio, it was lower among those with effective erythropoiesis than those with ineffective erythropoiesis. The effective group showed a statistically significant increase in reticulocyte maturation parameters compared to the ineffective group.

CONCLUSIONS

The findings show the pathogenesis of iron homeostasis in hemodialysis, the validity of hepcidin-25/erythroferrone ratio as a biomarker of erythropoiesis-stimulating agent effectiveness, and the advantageous monitoring of reticulocyte maturation measures to improve management of anemia-associated chronic kidney disease.

Impact of C-reactive protein on the effect of Roxadustat for the treatment of anemia in chronic kidney disease: a systematic review of randomized controlled trials

BACKGROUND

Chronic inflammation, reflected by an increased blood C-reactive protein (CRP) level, is common in patients with chronic kidney disease (CKD) and is involved in the development of renal anemia. This systematic review aims to investigate the impacts of CRP on the efficacy of hypoxia-inducible factor-prolyl hydroxylase inhibitors (HIF-PHIs) in the treatment of renal anemia in patients with CKD.

METHODS

We conducted a comprehensive search of electronic databases including Pubmed, Web of Science, Embase, Cochrane Library, CNKI, Wanfang, and the International Clinical Trials Registry Platform (ICTRP), from their inception to May 19, 2022. We systematically reviewed evidence from randomized controlled trials using HIF-PHIs for renal anemia treatment. The mean difference (MD) in changes in hemoglobin concentration (∆Hb) before and after treatment served as the meta-analysis outcome, utilizing a random-effects model. We compared groups with CRP levels greater than or equal to the upper limit of normal (ULN) and less than the ULN. Additionally, further analysis was conducted in the CRP ≥ ULN group comparing HIF-PHIs and erythropoiesis-stimulating agents (ESA).

RESULTS

A total of 7 studies from 6 publications were included in the analysis. In the comparison between the CRP ≥ ULN group and the CRP < ULN group, 524 patients from 4 studies were incorporated into the analysis. All patients received roxadustat as the primary intervention. The pooled results revealed no significant difference in ΔHb between patients with CRP ≥ ULN and CRP < ULN at baseline (Mean Difference: 0.00, 95% Confidence Interval: -0.32 to 0.33, P = 0.99). Moreover, within the CRP ≥ ULN group, three studies involving 1399 patients compared the efficacy of roxadustat and erythropoiesis-stimulating agents (ESAs). The results indicated no significant difference in ΔHb between patients treated with ESAs and HIF-PHIs (Mean Difference: 0.24, 95% Confidence Interval: -0.08 to 0.56, P = 0.14). In terms of medication dosage, an increase in ESA dose over time was observed across various studies, particularly evident in the CRP ≥ ULN group, while the dose of roxadustat remains constant over time and is not influenced by the baseline levels of CRP.

CONCLUSIONS

Our systematic review demonstrates that roxadustat exhibits similar efficacy across different CRP levels. Moreover, within the CRP ≥ ULN group, roxadustat can maintain efficacy comparable to ESA without the necessity for dose escalation.

TRIAL REGISTRATION

CRD42023396704.

The Influence of Precursor Depletion and dose Regimens on Resistance to Erythropoiesis-Stimulating Agents: Insights from Simulations with Instantaneous Dose-Adaptation Algorithm

Erythropoiesis-stimulating agents (ESAs) have been a common treatment for anemia associated with chronic kidney disease (CKD), while 10-20 % of patients continue to suffer from persistent anemia despite receiving ESA treatments. Our previous findings suggested that intensive ESA usage can cause resistance by depleting the erythroid precursor cells. Here, we used a mechanism-based pharmacokinetic/pharmacodynamic (PK/PD) model of ESAs and conducted simulations to evaluate the influence of dose regimens and other factors (such as administration route, individual PK/PD parameters, types of ESAs, and disease status) on ESA resistance with instantaneous dose adaptations in healthy populations and anemic patients. The simulated results show that instantaneous dose-adaptation can reduce ESA resistance, but up to 30 % of subjects still ended up developing ESA resistance in healthy populations. The Smax is markedly higher in hypo-responders than in normal-responders, while hypo-responders possess fewer precursors and experience a faster decline compared to normal-responders. There is a ceiling effect of increasing ESA dosage to improve HGB responses and reduce ESA resistance, and the limit is lower in anemic patients compared to healthy populations. Subcutaneous administrations and ESAs with longer half-lives lead to stronger HGB responses and less resistance at equivalent doses. Taken together, this study indicates that precursor depletion contributes to ESA resistance and dose regimens can greatly influence the occurrence of ESA resistance. Furthermore, ESA treatment for patients showing ESA resistance should avoid continuously increasing doses and instead consider stimulating the renewal of precursors.

Contemporary Practice of Anemia Treatment Among Dialysis Patients in the United States

Introduction

The treatment of anemia is a major activity in the care of patients undergoing maintenance hemodialysis (HD). The comparative effectiveness of new pharmacologic treatments, relative to erythropoiesis-stimulating agents (ESAs), should be anticipated on the bases of controlled trials and current practice. We describe the contemporary practice of anemia treatment in a national cohort of patients undergoing maintenance HD.

Methods

We analyzed the United States Renal Data System (USRDS) data to identify adult patients undergoing in-facility HD in 2016 to 2019. Using the Consolidated Renal Operations in a Web-Enabled Network (CROWNWeb) dataset, we identified hemoglobin and ESA utilization (agent and cumulative dose) during each patient-month, as well as intravenous (IV) iron utilization, ferritin, and transferrin saturation. We compared ESA dosing during the study era to dosing in the Normal Hematocrit Cardiac Trial (NHCT), conducted in the 1990s. We assessed ESA hyporesponsiveness by estimating the prevalence of the following: (i) high erythropoietin resistance index (ERI) and (ii) either 3 or 6 consecutive months with hemoglobin <10 g/dl.

Results

Nearly two-thirds of patient-months had hemoglobin of 10.0 to 11.9 g/dl. Mean ESA utilization was 76.7% per month, with increasing use of pegylated epoetin beta. ESA dosing was stable; epoetin alfa dosing was slightly lower than in the low-target arm of the NHCT. The prevalence of ESA hyporesponsiveness was 22.2% if defined by high ERI, but only 2.1% to 6.0% if defined by 3 to 6 consecutive months with hemoglobin <10 g/dl. Median transferrin saturation was 22.3% with high ERI and persistently low hemoglobin.

Conclusion

Hemoglobin and ESA dosing distributions are stable, with epoetin alfa dosing below the low-target arm of the NHCT. Persistently low hemoglobin occurs infrequently and may reflect iron depletion.

Relation between erythropoietin resistance and metabolic syndrome in hemodialysis patients: A multicentric propensity score matched analysis

Erythropoietin (EPO) resistance is frequently reported in hemodialysis (HD) patients. Metabolic syndrome (MetS) is a common biochemical condition that comprises central obesity, dyslipidemia, hypertension, and hyperglycemia. The present study aimed to assess the relation between MetS and EPO resistance in HD patients. The present multicentric study included 150 patients with EPO resistance and 150 patients without EPO resistance. Short-acting EPO resistance was diagnosed if the erythropoietin resistance index is ≥1.0 IU/kg/gHb. Comparison between patients with EPO resistance and patients without resistance revealed that the former group had significantly higher body mass index, lower hemoglobin levels, lower albumin levels, higher ferritin levels, and higher high-sensitivity C-reactive protein (hsCRP) levels. In addition, patients in the EPO resistance group had significantly higher frequency of MetS (75.3% vs 38.0%, p < 0.001) and higher number of MetS components (2.7 ± 1.3 vs 1.8 ± 1.6, p < 0.001). Multivariate logistic regression analysis identified lower albumin levels (OR (95% CI): 0.072 (0.016-0.313), p < 0.001), higher ferritin levels (OR (95% CI): 1.05 (1.033-1.066), p< 0.001), higher hsCRP levels (OR (95% CI): 1.041 (1.007-1.077), p = 0.018), and MetS (OR (95% CI): 36.68 (2.893-465.05), p = 0.005) as predictors of EPO resistance in the studied patients. The present study identified MetS as a predictor of EPO resistance in HD patients. Other predictors include serum ferritin, hsCRP, and albumin levels.

Individualization of the Dosage Regimen of Erythropoietin is Crucial in End-stage Renal Disease Patients

The objective of this study was to understand the utilization pattern of erythropoietin in end-stage renal disease patients, along with the effect of body weight and sex on the patients' responses. In this retrospective single-center study, 120 patients were included who were on a once weekly (n = 79), twice weekly (n = 37), or thrice weekly (n = 4) regimen. The doses of erythropoiesis-stimulating agents (ESA) were collected, and the erythropoietin resistance index (ERI) was determined. The Kruskal-Wallis test was used to evaluate the dose schedules, and the once-weekly regimen produced a greater response (P = 0.001). The asymptotic significance of Pearson's Chi-square-test equating the mean ERI and body mass index (BMI) was 0.034. No statistically significant correlation was estimated between sex and mean ERI (P = 0.201). Our study demonstrated that the once-weekly regimen dominated over the others in terms of efficacy, and individuals with a higher BMI were found to respond better to the ESA therapy.

Impact of Water Treatment on Anemia in Hemodialysis Patients

Introduction

The microbiological quality of water in the dialysate used in hemodialysis has been suggested as a contributor to inflammation, and a link between dialysate purity, inflammation, and responsiveness to erythropoietin therapy has been suggested in many studies. The level of endotoxin might induce inflammation and resistance to erythropoietin therapy in dialysis patients. We aimed to compare the effect of using the central dialysis fluid delivery system (CDDS) versus the single-patient dialysis fluid delivery system (SPDDS) on anemia in prevalent hemodialysis patients.

Methods

In a prospective cohort study, 100 adult prevalent hemodialysis patients with T-SAT ≥20% were divided into two equal groups: CDDS and SPDDS. Endotoxin in water sample and routine investigations (hemoglobin, serum Ca+, serum Po4-, PTH, and urea level) were done. CRP, erythropoietin resistivity index (ERI), and erythropoietin stimulating agents (ESAs) doses were assessed repeatedly to assess inflammatory and anemia states.

Results

Endotoxin level in the dialysis fluid of the CDDS group was significantly lower compared to the SPDDS group (0.05 vs. 0.11 EU/ml, P = 0.001). CRP level decreased significantly after 3 months in the CDDS group (P < 0.001) compared to the SPDDS group (P = 0.54), with significant improvement in the hemoglobin level and ERI at 3 months in the CDDS group and decrease in ESA requirements.

Conclusion

Improvement in dialysis liquid purity reduces inflammatory markers in prevalent hemodialysis patients, improves ERI, and decreases ESA requirements in renal anemia.

Physician Compliance with Computerized Clinical Decision Support System is a Complete Intermediate Factor in the Anemia Management of Patients with End-Stage Kidney Disease on Hemodialysis: A Retrospective Electronic Health Record Observational Study (Preprint)

BACKGROUND

Previous studies on clinical decision support systems (CDSSs) for the management of renal anemia in patients with end-stage kidney disease undergoing hemodialysis have previously focused solely on the effects of the CDSS. However, the role of physician compliance in the efficacy of the CDSS remains ill-defined.

OBJECTIVE

We aimed to investigate whether physician compliance was an intermediate variable between the CDSS and the management outcomes of renal anemia.

METHODS

We extracted the electronic health records of patients with end-stage kidney disease on hemodialysis at the Far Eastern Memorial Hospital Hemodialysis Center (FEMHHC) from 2016 to 2020. FEMHHC implemented a rule-based CDSS for the management of renal anemia in 2019. We compared the clinical outcomes of renal anemia between the pre- and post-CDSS periods using random intercept models. Hemoglobin levels of 10 to 12 g/dL were defined as the on-target range. Physician compliance was defined as the concordance of adjustments of the erythropoietin-stimulating agent (ESA) between the CDSS recommendations and the actual physician prescriptions.

RESULTS

We included 717 eligible patients on hemodialysis (mean age 62.9, SD 11.6 years; male n=430, 59.9%) with a total of 36,091 hemoglobin measurements (average hemoglobin and on-target rate were 11.1, SD 1.4, g/dL and 59.9%, respectively). The on-target rate decreased from 61.3% (pre-CDSS) to 56.2% (post-CDSS) owing to a high hemoglobin percentage of >12 g/dL (pre: 21.5%; post: 29%). The failure rate (hemoglobin <10 g/dL) decreased from 17.2% (pre-CDSS) to 14.8% (post-CDSS). The average weekly ESA use of 5848 (SD 4211) units per week did not differ between phases. The overall concordance between CDSS recommendations and physician prescriptions was 62.3%. The CDSS concordance increased from 56.2% to 78.6%. In the adjusted random intercept model, the post-CDSS phase showed increased hemoglobin by 0.17 (95% CI 0.14-0.21) g/dL, weekly ESA by 264 (95% CI 158-371) units per week, and 3.4-fold (95% CI 3.1-3.6) increased concordance rate. However, the on-target rate (29%; odds ratio 0.71, 95% CI 0.66-0.75) and failure rate (16%; odds ratio 0.84, 95% CI 0.76-0.92) were reduced. After additional adjustments for concordance in the full models, increased hemoglobin and decreased on-target rate tended toward attenuation (from 0.17 to 0.13 g/dL and 0.71 to 0.73 g/dL, respectively). Increased ESA and decreased failure rate were completely mediated by physician compliance (from 264 to 50 units and 0.84 to 0.97, respectively).

CONCLUSIONS

Our results confirmed that physician compliance was a complete intermediate factor accounting for the efficacy of the CDSS. The CDSS reduced failure rates of anemia management through physician compliance. Our study highlights the importance of optimizing physician compliance in the design and implementation of CDSSs to improve patient outcomes.

Erythropoietin-Stimulating Agent Hyporesponsiveness in Patients Living with Chronic Kidney Disease

BACKGROUND

Erythropoietin-stimulating agent (ESA) hyporesponsiveness is commonly observed in patients with anemia secondary to chronic kidney disease (CKD). Because of its complexity, a global consensus on how we should define ESA hyporesponsiveness remains unavailable. The reported prevalence and demographic information on ESA hyporesponsiveness within the CKD population are variable with no consensus definition.

SUMMARY

ESA hyporesponsiveness is defined as having no increase in hemoglobin concentration from baseline after the first month of treatment on appropriate weight-based dosing. The important factors associated with ESA hyporesponsiveness include absolute or functional iron deficiency, inflammation, and uremia. Hepcidin has been demonstrated to play an important role in this process. Mineral bone disease secondary to CKD and non-iron malnutrition among other factors are also associated with ESA hyporesponsiveness. There is continued debate toward determining a gold-standard treatment pathway to manage ESA hyporesponsiveness. The development of hypoxia-inducing factor-stabilizers brings new insights and opportunities in the management of ESA hyporesponsiveness.

KEY MESSAGE

Management of ESA hyporesponsiveness involves a comprehensive multidisciplinary team approach to address its risk factors. The progression of basic and clinical research on identifying risk factors and management of ESA hyporesponsiveness brings greater hope on finding solutions to eventually tackling one of the most difficult problems in the topic of anemia in CKD.

Effects of the route of erythropoietin administration on hemoglobin variability and cardiovascular events in hemodialysis patients

Introduction

Despite of the routine use of erythropoietin in hemodialysis patients to correct anemia, its administration route's effects on hemoglobin variability and cardiovascular events remain elusive. Herein, we determined different erythropoietin administration routes' effects on hemoglobin variability in hemodialysis patients and the associated factors of hemoglobin variability and cardiovascular events.

Methods

This is a post hoc analysis of a prospective, controlled, randomized, unblinded study with 78 Korean hemodialysis patients receiving intravenous (n = 40) or subcutaneous (n = 38) erythropoietin therapy. We evaluated hemoglobin variability by calculating the frequency of hemoglobin measurements outside the target range during all visits. The high-frequency group was defined by those with hemoglobin variability over the median value (25%) while the low-frequency group was defined by those with hemoglobin variability of <25%.

Results

In this analysis, 37 patients (51.1%) were males, and the mean age was 50.6 ± 12.5 years. The frequency of the value being outside the target hemoglobin range was higher in the subcutaneous group compared to the intravenous group (p = 0.03). The low-frequency group required significantly lower erythropoietin doses compared to the high-frequency group. In the adjusted Cox analysis, the parameter high group was a significant independent risk factor for cardiovascular events (p = 0.03).

Conclusion

The risk out of the target hemoglobin range increased with subcutaneous administration compared with intravenous erythropoietin administration in hemodialysis patients. An increased frequency of the value being outside the target hemoglobin range was also associated with an increased risk of cardiovascular events.

Factors associated with hepcidin-25 levels in maintenance hemodialysis patients

This study aimed to investigate the factors that are independently associated with hepcidin-25 and its relationship with doses of erythropoiesis-stimulating agents (ESAs) and intravenous iron in stable maintenance hemodialysis patients (smHD) stratified by ESAs administration. In 103 adult smHD (ESAs therapy (N = 64) and ESAs-free (N = 39)), median values of biologically active hepcidin-25 (chemiluminescent direct ELISA assay) and ferritin levels were significantly higher whereas red blood cell count, hemoglobin, and hematocrit values were lower in ESAs therapy compared to ESAs-free group (P < .001, for all). Our results suggest that ESAs-independent smHD exhibit supposedly normal hepcidin-25 levels and preserved iron homeostasis, with a lower degree of anemia. The results of our multivariable model indicate that hepcidin-25 levels are independently and positively associated with iron stores and inflammation, and inversely with active erythropoiesis, regardless of ESAs administration. Maintenance ESAs and the intravenous iron dose were not related to hepcidin-25 levels.

Association of erythropoietin resistance and fibroblast growth factor 23 in dialysis patients: Results from the Japanese Dialysis Outcomes and Practice Patterns Study

BACKGROUND

Fibroblast growth factor 23 (FGF23) plays an important role in chronic kidney disease (CKD)-related mineral and bone disorders. High FGF23 levels are associated with increased risk of anaemia in non-haemodialysis CKD patients. FGF23 also negatively regulates erythropoiesis in mice. We hypothesized that higher FGF23 levels are associated with increased erythropoietin hyporesponsiveness among haemodialysis patients.

METHODS

The study included 1044 patients from the Japanese Dialysis Outcomes and Practice Patterns Study (J-DOPPS) phase 5 (2012-2015). The outcome was erythropoiesis-stimulating agent hyporesponsiveness (ESA-hypo), defined as mean Hgb <10 g/dL and standardized mean ESA dose >6000 u/week over 4 months following FGF23 measurement. The association between ESA-hypo and FGF23 was estimated using multivariable-adjusted logistic generalized estimating equation regression models.

RESULTS

Patients with higher levels of FGF23 were younger and had higher levels of serum albumin, creatinine, albumin-corrected calcium, phosphorus, PTH, 25(OH)-vitamin D, and had higher percentages of intravenous (IV) iron, IV vitamin D and cinacalcet use. ESA-hypo was present in 144 patients (13.8%). Compared with the third quintile of FGF23 levels, the odds ratio (95% CI) of ESA-hypo was 2.14 (0.99, 4.62) and 1.74 (0.74, 4.11) for the first and fifth quintiles, respectively.

CONCLUSION

The lowest and highest levels of FGF23 were associated with higher odds of ESA-hypo in patients on maintenance haemodialysis, although the associations were not statistically significant. The relationship between FGF23 and anaemia, and particularly the increased risks of ESA-hypo at low FGF23 levels which might be the result of energy saving, must be confirmed in larger clinical studies.

Population Pharmacodynamic Modeling of Epoetin Alfa in End-Stage Renal Disease Patients Receiving Maintenance Treatment Using Bayesian Approach

The ability to control dosage regimens of erythropoiesis-stimulating agents (ESAs) to maintain a desired hemoglobin (HGB) target is still elusive. We utilized a Bayesian approach and informative priors to characterize HGB profiles, using simulated drug concentrations, in patients with end-stage renal disease receiving maintenance doses of epoetin alfa. We also demonstrated an adaptive Bayesian method, applied to individual patients, to improve the accuracy of HGB predictions over time. The results showed that sparse HGB data from daily clinical practice were characterized successfully. The adaptive Bayesian method effectively improved the accuracy of HGB predictions by updating the individual model with new data accounting for within-subject changes over time. The Bayesian approach presented leverages existing knowledge of the model parameters and has a potential utility in clinical practice to individualize dosage regimens of epoetin alfa and ESAs to achieve target HGB. Further studies are warranted to develop an application for practical use.

Enhanced prediction of hemoglobin concentration in a very large cohort of hemodialysis patients by means of deep recurrent neural networks

Erythropoiesis Stimulating Agents (ESAs) have become a standard anemia management tool for End Stage Renal Disease (ESRD) patients. However, dose optimization constitutes an extremely challenging task due to huge inter and intra-patient variability in the responses to ESA administration. Current data-based approaches to anemia control focus on learning accurate hemoglobin prediction models, which can be later utilized for testing competing treatment choices and choosing the optimal one. These methods, despite being proven effective in practice, present several shortcomings which this paper intends to tackle. Namely, they are limited to a small cohort of patients and, even then, they fail to provide suggestions when some strict requirements are not met (such as having a three month history prior to the prediction). Here, recurrent neural networks (RNNs) are used to model whole patient histories, providing predictions at every time step since the very first day. Furthermore, an unprecedented amount of data (∼110,000 patients from many different medical centers in twelve countries, without exclusion criteria) was used to train it, thus allowing it to generalize for every single patient. The resulting model outperforms state-of-the-art Hemoglobin prediction, providing excellent results even when tested on a prospective dataset. Simultaneously, it allows to bring the benefits of algorithmic anemia control to a very large group of patients.

Inflammation and Erythropoiesis-Stimulating Agent Response in Hemodialysis Patients: A Self-matched Longitudinal Study of Anemia Management in the Dialysis Outcomes and Practice Patterns Study (DOPPS)

Rationale & Objective

Previous studies of inflammation and anemia management in hemodialysis (HD) patients may be biased due to patient differences. We used a self-matched longitudinal design to test whether new inflammation, defined as an acute increase in C-reactive protein (CRP) level, reduces hemoglobin response to erythropoiesis-stimulating agent (ESA) treatment.

Study Design

Self-matched longitudinal design.

Setting & Participants

3,568 new inflammation events, defined as CRP level > 10 mg/L following a 3-month period with CRP level ≤ 5 mg/L, were identified from 12,389 HD patients in the Dialysis Outcomes and Practice Patterns Study (DOPPS) phases 4 to 6 (2009-2018) in 10 countries in which CRP is routinely measured.

Predictor

“After” (vs “before”) observing a high CRP level.

Outcomes

Within-patient changes in hemoglobin level, ESA dose, and ESA hyporesponsiveness (hemoglobin < 10 g/dL and ESA dose > 6,000 [Japan] or >8,000 [Europe] U/wk).

Analytical Approach

Linear mixed models and modified Poisson regression.

Results

Comparing before with after periods, mean hemoglobin level decreased from 11.2 to 10.9 g/dL (adjusted mean change, −0.26 g/dL), while mean ESA dose increased from 6,320 to 6,960 U/wk (adjusted relative change, 8.4%). The prevalence of ESA hyporesponsiveness increased from 7.6% to 12.3%. Both the unadjusted and adjusted prevalence ratios of ESA hyporesponsiveness were 1.68 (95% CI, 1.48-1.91). These associations were consistent in sensitivity analyses varying CRP thresholds and were stronger when the CRP level increase was sustained over the 3-month after period.

Limitations

Residual confounding by unmeasured time-varying risk factors for ESA hyporesponsiveness.

Conclusions

In the 3 months after HD patients experienced an increase in CRP levels, hemoglobin levels declined quickly, ESA doses increased, and the prevalence of ESA hyporesponsiveness increased appreciably. Routine CRP measurement could identify inflammation as a cause of worsened anemia. In turn, these findings speak to a potentially important role for anemia therapies that are less susceptible to the effects of inflammation.

Increased mortality in haemodialysis patients administered high doses of erythropoiesis-stimulating agents: a propensity score-matched analysis

Background

Erythropoiesis-stimulating agents (ESAs) are widely used to treat anaemia in patients with chronic kidney disease. The issue of ESA safety has been raised in multiple studies, with correlates derived for elevated cancer incidence and mortality. Whether these associations are related to ESA dose or the typology of the patient remains obscure.

Methods

A multicentre, observational retrospective propensity score-matched study was designed to analyse the effects of weekly ESA dose in 1679 incident haemodialysis (HD) patients. ESA administration was according to standard medical practice. Patients were grouped as quintiles, according to ESA dose, in order to compare mortality and hospitalization data. Using propensity score matching (PSM), we defined two groups of 324 patients receiving weekly threshold ESA doses of either > or ≤8000 IU.

Results

Kaplan-Meier survival curves indicated significant increases in the risk of mortality in patients administered with high doses of ESAs (>8127.4 IU/week). Multivariate Cox models identified a high ESA dose as an independent predictor for all-cause and cardiovascular (CV) mortality. Moreover, logistic regression models identified high ESA doses as an independent predictor for all-cause, CV and infectious hospitalization. PSM analyses confirmed that weekly ESA doses of >8000 IU constitute an independent predictor of all-cause mortality and hospitalization, even though the adjusted cohort displayed the same demographic features, inflammatory profile, clinical HD parameters and haemoglobin levels.

Conclusions

Our data suggest that ESA doses of >8000 IU/week are associated with an increased risk of all-cause mortality and hospitalization in HD patients.

Statin therapy and erythropoiesis-stimulating agent hyporesponsiveness in patients with nondialysis chronic kidney disease: A retrospective study in Beijing, China

Erythropoiesis-stimulating agents (ESAs) are frequently used among patients with renal anemia, while a significant proportion of patients exhibit ESA hyporesponsiveness despite adequate dosing. Previous studies have suggested an inverse association between ESA hyporesponsiveness and statin use among patients receiving dialysis therapy. However, studies based on predialysis patients are extremely limited.Based on electronic medical records of a tertiary hospital in Beijing, China between April 2010 and April 2015, we investigated the association between statin use and ESA hyporesponsiveness among patients with predialysis-chronic kidney disease (CKD).Altogether 232 patients with CKD initiating ESA therapy and with hemoglobin levels monitored for at least 6 months were included in our analyses. Among them, 77 (38.5%) were long-term statin users (regular statin treatment for more than 3 months) before ESA initiation. Overall, 6.5% of the statin users and 17.1% of nonusers were considered to have ESA hyporesponsiveness. Long-term statin therapy was significantly associated with a lower proportion of ESA hyporesponsiveness in fully adjusted model (odds ratio 0.15, 95% confidence interval: 0.03-0.64).We found that long-term statin therapy was inversely associated with ESA hyporesponsiveness among predialysis patients with CKD. Further studies are needed to validate our observations, and to explore the potential mechanisms between ESA resistance and statin therapy.

Definition and Validation of a Novel Metric of Erythropoiesis-Stimulating Agent Response in Hemodialysis Patients

Erythropoiesis-stimulating agents (eg, epoetin alfa) are the primary treatment for anemia in patients with end-stage renal disease. Hemoglobin variability in and out of a narrow target range is common and associated with higher morbidity and mortality risk. More robust erythropoiesis-stimulating agent response metrics are needed to define optimal dosing and their association with clinical outcomes. In this cross-sectional, single-center, retrospective study, 49 patients with end-stage renal disease on hemodialysis were followed over 12 months. To quantify hemoglobin deviations outside the target range (10-12 g/dL), the area under the curve of hemoglobin versus time over a 12-month period (AUC-HGB) was calculated using the trapezoidal rule. Patients were categorized into 4 responder groups based on AUC-HGB quartiles. Comparative analyses of demographic and clinical characteristics between responder groups were performed. Correlations between AUC-HGB, erythropoietin resistance index, and time within therapeutic range were calculated. There were no significant differences in laboratory and dialysis parameters between responder groups except hemoglobin concentration and epoetin alfa dose. There was a negative correlation between AUC-HGB and time within therapeutic range (r = -.92; P < .001) and hemoglobin concentration (r = -.85; P < .01), indicating internal validity of the metric. There was a positive correlation between AUC-HGB and erythropoietin resistance index (r = .70; P < .001) indicating external validity. The poor response group received a higher median epoetin alfa dose (160 U/kg/week) compared to the excellent response group (68.8 U/kg/week; P < .001) with a similar number of dose changes between the groups. AUC-HGB is a valid marker of epoetin alfa response and should be considered in future analyses of larger populations.

Response to erythropoietin in pediatric patients with chronic kidney disease: insights from an in vitro bioassay

BACKGROUND

Decreased production of erythropoietin (EPO) is a major cause of anemia associated with chronic kidney disease (CKD). Treatment with recombinant human EPO (rHuEPO) improves patients' quality of life and survival; however, there is a marked variability in response to rHuEPO. At present, no available laboratory test is capable of evaluating responsiveness to EPO treatment. The aim of the present study was to use an in vitro bioassay to estimate the effect of uremic environment on EPO-dependent erythroid cell proliferation.

METHODS

EPO-dependent human erythroleukemia cells (UT-7) were incubated with exogenous EPO (2 u/ml) and sera obtained from 60 pediatric patients (aged 1-23 years). Three groups were studied: (1) 12 children on dialysis (4 peritoneal, 8 hemodialysis); (2) 28 patients with CKD 1-5 (not on dialysis), and (3) 20 healthy children.

RESULTS

Sera from dialysis patients inhibited UT-7 cell growth compared to the CKD group and healthy controls at 48 h (p = 0.003 and p = 0.04, respectively) and 72 h of culture (p = 0.02 and p = 0.07, respectively). In 18 patients treated with rHuEPO, a significant inverse correlation was found between the EPO resistance index and cell proliferation at 48 h (p = 0.007, r = - 0.63) and 72 h (p = 0.03, r = - 0.52).

CONCLUSIONS

Our findings support the presence of erythropoiesis inhibitory substances in uremic sera. EPO/EPO-R-dependent mechanisms may play a role in inhibiting erythropoiesis. The in vitro bioassay described herein may serve as an indicator of rHuEPO responsiveness which may encourage further investigation of underlying mechanisms of EPO resistance.

Obesity may be erythropoietin dose-saving in hemodialysis patients

Background

In dialysis patients, the obesity-survival paradox still requires an explanation. Anemia and high doses of erythropoiesis-stimulating agents (ESAs) are associated with worse outcomes in the hemodialysis (HD) population. In the present study, we explored the relation between obesity and anemia control in a sample of maintenance HD patients in Egypt.

Methods

This multicenter observational study included 733 patients on maintenance HD from 9 hemodialysis centers in Egypt. Clinical and laboratory data as well as average doses of ESAs and parenteral iron were recorded. The erythropoietin resistance index (ERI) was calculated.

Results

Obesity, defined as a body mass index (BMI) ≥ 30 kg/m², was present in 22.6% of the studied population. The target hemoglobin level (10.0–11.5 g/dL) was achieved in 27.3% of non-obese and 25.3% of obese patients, with no significant difference. The median serum ferritin and the values of transferrin saturation index did not differ significantly between these two groups. The weekly ESA dose was significantly lower in obese than in non-obese patients (P = 0.0001). A trend toward higher ESA doses and ERI values was observed in patients with lower BMIs (P < 0.0001). Multiple linear regression revealed that the BMI and urea reduction ratio were the strongest predictors of the ERI.

Conclusion

Our study adds more evidence to obesity-associated advantages in HD patients. BMI may determine ESA response, with better responses observed in patients with higher BMIs.

Residual renal function in chronic dialysis is not associated with reduced erythropoietin-stimulating agent dose requirements: a cross-sectional study

BACKGROUND

Anaemia is a very common problem in patients with end-stage kidney disease (ESKD) and the use of erythropoietin-stimulating agents (ESA) has revolutionised its treatment. Residual renal function (RRF) is associated with a reduction in ESA resistance and mortality in chronic dialysis. The primary aim was to establish whether RRF has an association with ESA dose requirements in ESKD patients receiving chronic dialysis.

METHODS

A single center, cross-sectional study involving 100 chronic dialysis patients was conducted from December 2015 to May 2016. Participants were divided into two groups depending on presence of RRF, which was defined as a 24-h urine sample volume of ≥ 100 ml. Erythropoietin resistance index [ERI = total weekly ESA dose (IU)/weight (kg)/haemoglobin concentration (g/dL] was used as a measure of ESA dose requirements.

RESULTS

There was no difference in ERI between those with RRF as compared to those without (9.5 versus 11.0, respectively; P = 0.45). Also, ERI did not differ between those receiving haemodialysis as compared with peritoneal dialysis (10.8 versus 10.2, respectively; P = 0.84) or in those using renin-angiotensin system (RAS) blockers as compared with no RAS blocker use (11.6 versus 9.2, respectively; P = 0.10). Lower ERI was evident for those with cystic kidney disease as compared to those with other causes of ESKD (6.9 versus 16.5, respectively; P = 0.32) although this did not reach statistical significance. Higher ERI was found in those with evidence of systemic inflammation as compared to those without (16.5 versus 9.5, respectively; P = 0.003).

CONCLUSIONS

There was no association between RRF and ESA dose requirements, irrespective of dialysis modality, RAS blocker use, primary renal disease or hyperparathyroidism.

Association between resistance to erythropoiesis-stimulating agents and carnitine profile in patients on maintenance haemodialysis

OBJECTIVE

Patients on dialysis are in a chronic carnitine-deficient state. This condition may be associated with abnormalities in fatty acid and organic acid metabolism; however, the details are unknown. We investigated the association between carnitine profiles before and after dialysis and the erythropoiesis-stimulating agent (ESA) resistance index (ERI), which is a significant prognostic factor in patients on maintenance haemodialysis.

METHODS

This was a cross-sectional study. We measured the carnitine profile of 79 patients on maintenance haemodialysis before and after dialysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The associations between the ERI and pre-dialysis carnitine profile, removal rate of various carnitines, and previously-reported ERI-related factors were investigated. Significant factors were determined with stepwise multiple regression analysis and validated with the bootstrap method. SPSS version 22.0 was used for analysis, and P < 0.05 was considered statistically significant.

RESULTS

The removal rate of long-chain acylcarnitine with dialysis was lower than that of short-chain or medium-chain acylcarnitines. Stepwise multiple regression analysis (n = 79) demonstrated that 3-hydroxy isovalerylcarnitine (C5-OH, P < 0.001, β = -0.469) and stearoylcarnitine (C18, P < 0.001, β = 0.390) were independent significant factors (R² = 0.239) of ERI. The bootstrap method similarly indicated these two to be significant factors.

CONCLUSION

ERI positively correlated with long-chain C18 acylcarnitine and negatively correlated with short-chain C5-OH acylcarnitine. C5-OH and C18 acylcarnitines at baseline might be contributing factors in distinguishing responders from nonresponders after L-carnitine administration.