Longitudinal trends in serum ferritin levels and associated factors in a national incident hemodialysis cohort

Iron Management and Anemia in Patients on the Active Kidney Transplant List

INTRODUCTION

Iron metabolism disorders and anemia are one of the main complications of end-stage renal disease that may affect the evaluation process for kidney transplantation. The study aimed to assess the iron metabolism in hemodialysis patients in relation to waiting list status.

STUDY METHOD

The study included 5068 hemodialysis patients, including those on the active waiting list (N = 449) and those who were not eligible for the waitlist (N = 4619). Demographic and biochemical data, Charlson's comorbidity index, duration of hemodialysis therapy and, respectively, hemoglobin, ferritin, and transferrin saturation levels were compared in both groups of patients.

RESULTS

Patients on the active waiting list were significantly younger -53.2 vs 67.2 years (P < .001), with a lower Charlson comorbidity index score: 3.33 vs 4.42 (P < .001). The duration of hemodialysis therapy was similar: 66.0 vs 63.2 months (P = .416), the incidence of anemia according to World Health Organization (90.6%, vs 91.2%) and KDIGO (72.4% vs 70.4%). The degree of anemia correction in terms of hemoglobin concentration and transferrin saturation was comparable in both groups and amounted to an average of 10.9 g/dL (P = .349) for hemoglobin concentration and 32.7% vs 33.4% (P = .513) for transferrin saturation. However, there was a statistically significant difference in ferritin concentration: 554 ug/L vs 733 ug/L (P = .001).

CONCLUSIONS

Patients on the active list have significantly lower ferritin levels despite similar duration of hemodialysis treatment and comparable hemoglobin values. This may be due to lower inflammation, and less frequent blood transfusions, and lead to a lower risk of immunization and an increased chance of potential kidney transplantation.

Serum ferritin and neutrophil-to-lymphocyte ratio predict all-cause mortality in patients receiving maintenance hemodialysis: a prospective study

Introduction: Maintenance hemodialysis is an effective treatment for end-stage renal disease patients. A critical factor contributing to the deterioration and death of maintenance hemodialysis patients is inflammation. Therefore, we focused on two inflammatory markers, serum ferritin and neutrophil-to-lymphocyte ratio, to speculate whether they could predict the prognosis of maintenance hemodialysis patients. Patients and methods: We followed 168 patients with maintenance hemodialysis from July 2019 to July 2022 with the endpoint of all-cause death or follow-up completion. Receiver operating characteristic curves were plotted to assess the values of serum ferritin, neutrophil-to-lymphocyte ratio and serum ferritin combined with neutrophil-to-lymphocyte ratio to predict the outcomes of maintenance hemodialysis patients. Kaplan-Meier survival curves were constructed to compare survival rates over time. Results: Receiver operating characteristic curves demonstrated that the best cut-off value of serum ferritin for predicting the prognosis of maintenance hemodialysis patients was 346.05 μg/L, and that of neutrophil-to-lymphocyte ratio was 3.225. Furthermore, a combination of both had a more excellent predicting value than either index (p < 0.05). Kaplan-Meier survival curve analyses revealed that low serum ferritin levels and low neutrophil-to-lymphocyte ratio had a higher probability of survival than high ferritin levels and high neutrophil-to-lymphocyte ratio, separately. Conclusion: Elevated serum ferritin and neutrophil-to-lymphocyte ratio are closely related to all-cause mortality among maintenance hemodialysis patients, for which they may be predictors of all-cause mortality. Additionally, the combination of the two has a much higher predictor value for the prognosis of maintenance hemodialysis patients.

Persistent Increase in Serum Ferritin Levels despite Converting to Permanent Vascular Access in Pediatric Hemodialysis Patients: Pediatric Nephrology Research Consortium Study

Our objective was to examine serum ferritin trends after conversion to permanent vascular access (PVA) among children who started hemodialysis (HD) using tunneled cuffed catheters (TCC). Retrospective chart reviews were completed on 98 subjects from 20 pediatric HD centers. Serum ferritin levels were collected at the creation of PVA and for two years thereafter. There were 11 (11%) arteriovenous grafts (AVG) and 87 (89%) arteriovenous fistulae (AVF). Their mean TCC use was 10.4 ± 17.3 months. Serum ferritin at PVA creation was elevated at 562.64 ± 492.34 ng/mL, increased to 753.84 ± 561.54 ng/mL (p = < 0.001) in the first year and remained at 759.60 ± 528.11 ng/mL in the second year (p = 0.004). The serum ferritin levels did not show a statistically significant linear association with respective serum hematocrit values. In a multiple linear regression model, there were three predictors of serum ferritin during the first year of follow-up: steroid-resistant nephrotic syndrome as primary etiology (p = 0.035), being from a center that enrolled >10 cases (p = 0.049) and baseline serum ferritin level (p = 0.017). Increasing serum ferritin after conversion to PVA is concerning. This increase is not associated with serum hematocrit trends. Future studies should investigate the correlation of serum transferrin saturation and ferritin levels in pediatric HD patients.

Post-mortem liver and bone marrow iron quantification in haemodialysis patients: A prospective cohort study

Background

Magnetic resonance liver scans indicate that iron overload is common in haemodialysis (HD) patients. However, histological evidence is scarce.

Methods

Liver biopsy and bone marrow aspirate were obtained in the first 24h post mortem from 21 adult HD patients. Biochemical liver iron content (LIC) was quantified by electrothermal atomization atomic absorption spectrophotometry. Tissue iron deposition was graded in the liver and bone marrow using Scheuer and Gale's criteria, respectively.

Findings

Median LIC was 42.5 (22.9-69.7) μmol/g and the majority (n=11; 57%) had mild to moderate liver iron overload (LIC >36 μmol/g). Scheuer grade was 2 (1-3) and 13 (62%) of liver biopsies had increased (> 1) iron deposition. In the bone marrow, median Gale's grade was 3 (3-4) and 9 (45%) patients had increased (>3) iron content.

Contrary to old autopsy studies, done in the pre-erythropoiesis-stimulating agents (ESAs) era, both liver and bone marrow were iron replete and showed a positive correlation (r=0.71, p<0.001).

Ferritin proved to have a good diagnostic accuracy for liver iron overload (0.87 95% CI 0.71-1.00) with an optimal cut-off value of 422 ng/ml. Haemoglobin was negatively associated with both LIC (r= -0.46, p=0.04) and iron content in the bone marrow (p=0.04). Patients with increased LIC had higher resistance to ESAs (p=0.02), yet no association with previous IV iron therapy.

Interpretation

In the majority of HD patients there was iron accumulation in both the liver and bone marrow that associated with anaemia severity and resistance to ESAs, suggesting a blocking mechanism of iron's utilization.

Funding

None.

Biomarkers of iron metabolism in chronic kidney disease

Iron is the most abundant transition metal in the human body and an essential element required for growth and survival. Our understanding of the molecular control of iron metabolism has increased dramatically over the past 20 years due to the discovery of hepcidin, which regulates the uptake of dietary iron and its mobilization from macrophages and hepatic stores. Anemia and iron deficiency are common in chronic kidney disease. The pathogenesis of anemia of chronic kidney disease is multifactorial. Correction of anemia requires two main treatment strategies: increased stimulation of erythropoiesis, and maintenance of an adequate iron supply to the bone marrow. However, there are still many uncertainties in regard to iron metabolism in patients with chronic kidney disease and in renal replacement therapy. The aim of this review was to summarize the current knowledge on iron metabolism in this population, including new biomarkers of iron status. There is an area of uncertainty regarding diagnostic utility of both erythroferrone (ERFE) and hepcidin in end-stage renal disease (ESRD) patients. Higher concentration of hepcidin in oligoanuric patients may reflect decreased renal clearance. Furthermore, the hepcidin-lowering effect of ERFE in ESRD patients treated with erythropoiesis-stimulating agents (ESAs) may be blunted by underlying inflammation and concomitant iron treatment. Thus, future studies should validate the use of ERFE as a biomarker of erythropoiesis and predictor of response to iron and ESA therapy in dialysis-dependent patients.

Iron Deficiency in Chronic Kidney Disease: Updates on Pathophysiology, Diagnosis, and Treatment

Anemia is a complication that affects a majority of individuals with advanced CKD. Although relative deficiency of erythropoietin production is the major driver of anemia in CKD, iron deficiency stands out among the mechanisms contributing to the impaired erythropoiesis in the setting of reduced kidney function. Iron deficiency plays a significant role in anemia in CKD. This may be due to a true paucity of iron stores (absolute iron deficiency) or a relative (functional) deficiency which prevents the use of available iron stores. Several risk factors contribute to absolute and functional iron deficiency in CKD, including blood losses, impaired iron absorption, and chronic inflammation. The traditional biomarkers used for the diagnosis of iron-deficiency anemia (IDA) in patients with CKD have limitations, leading to persistent challenges in the detection and monitoring of IDA in these patients. Here, we review the pathophysiology and available diagnostic tests for IDA in CKD, we discuss the literature that has informed the current practice guidelines for the treatment of IDA in CKD, and we summarize the available oral and intravenous (IV) iron formulations for the treatment of IDA in CKD. Two important issues are addressed, including the potential risks of a more liberal approach to iron supplementation as well as the potential risks and benefits of IV versus oral iron supplementation in patients with CKD.

Individualized anemia management in a dialysis facility - long-term utility as a single-center quality improvement experience

Background: Standard protocol-based approaches to erythropoiesis stimulating agent (ESA) dosing in anemia management of end-stage renal disease (ESRD) fail to address the inter-individual variability in patient’s response to ESA. We conducted a single-center quality improvement project to investigate the long-term performance of a computer-designed dosing system. Materials and methods: The study was a retrospective case-control study with long-term follow-up. All hemodialysis patients who received treatment at University Kidney Center (Louisville, KY, USA) between September 1, 2009, and March 31, 2017, were included. We implemented an individualized ESA dosing algorithm into an electronic health records database software to provide patient-specific ESA dose recommendations to anemia managers at monthly intervals. The primary outcome was the percentage of hemoglobin (Hb) concentrations between 10 and 12 g/dL during the case-control study and 9 and 11 g/dL during follow-up. Secondary outcomes were intra- and inter-individual Hb variability. For the case-control study, we compared outcomes over 12 months before and after implementation of the algorithm. Subjects served as their own controls. We used the last Hb concentration of the month and ESA dose per week. Long-term follow-up examined trends in proportion within the target range, Hb, and ESA dose. Results: Individualized ESA dosing in 56 subjects was associated with a moderate (6.6%) increase of mean Hb maintenance within target over the 12-month observation period (62.7% before vs. 69.3% after, p = 0.063). Intra-individual mean Hb variability decreased (1.1 g/dL before vs. 0.8 g/dL after, p < 0.001), so did inter-individual mean Hb variability (1.2 g/dL before vs. 1.0 g/dL after, p = 0.010). Long-term follow-up in 233 subjects for 42 months demonstrated stability of the achieved Hb despite an increasing ESA resistance in the patient population. Conclusion: Implementation of the individualized ESA dosing algorithm facilitates improvement in Hb maintenance within target, decreases Hb variability and reduces the dose of ESA required to achieve Hb target.

Relationships between iron dose, hospitalizations and mortality in incident haemodialysis patients: a propensity-score matched approach

Background

Intravenous iron management is common in the haemodialysis population. However, the safest dosing strategy remains uncertain, in terms of the risk of hospitalization and mortality. We aimed to determine the effects of cumulative monthly iron doses on mortality and hospitalization.

Methods

This multicentre observational retrospective propensity-matched score study included 1679 incident haemodialysis patients. We measured baseline demographic variables, haemodialysis clinical parameters and laboratory analytical values. We compared outcomes among quartiles of cumulative iron dose (mg/kg/month). We implemented propensity-score matching (PSM) to reduce confounding due to indication. In the PSM cohort (330 patients), we compared outcomes between groups that received cumulative iron doses above and below 5.66 mg/kg/month.

Results

Kaplan-Meier analyses showed that the high iron dose group had significantly worse survival than the low iron dose group. A univariate analysis indicated that the monthly iron dose could significantly predict mortality. However, a multivariate regression did not confirm that finding. The multivariate regression analysis revealed that iron doses  >5.58 mg/kg/month were not associated with elevated mortality risk, but they were associated with elevated risks of all-cause and cardiovascular-related hospitalizations. These results were ratified in the PSM population.

Conclusions

Intravenous iron administration is advisable for maintaining haemoglobin levels in patients that receive haemodialysis. Our data suggested that large monthly iron doses, adjusted for body weight, were associated with more hospitalizations, but not with mortality or infection-related hospitalizations.

Modeling longitudinal data and its impact on survival in observational nephrology studies: tools and considerations

Nephrologists and kidney disease researchers are often interested in monitoring how patients' clinical and laboratory measures change over time, what factors may impact these changes, and how these changes may lead to differences in morbidity, mortality, and other outcomes. When longitudinal data with repeated measures over time in the same patients are available, there are a number of analytical approaches that could be employed to describe the trends and changes in these measures, and to explore the associations of these changes with outcomes. Researchers may choose a streamlined and simplified analytic approach to examine trajectories with subsequent outcomes such as estimating deltas (subtraction of the last observation from the first observation) or estimating per patient slopes with linear regression. Conversely, they could more fully address the data complexity by using a longitudinal mixed model to estimate change as a predictor or employ a joint model, which can simultaneously model the longitudinal effect and its impact on an outcome such as survival. In this review, we aim to assist nephrologists and clinical researchers by reviewing these approaches in modeling the association of longitudinal change in a marker with outcomes, while appropriately considering the data complexity. Namely, we will discuss the use of simplified approaches for creating predictor variables representing change in measurements including deltas and patient slopes, as well more sophisticated longitudinal models including joint models, which can be used in addition to simplified models based on the indications and objectives of the study as warranted.

Serum Ferritin Variations and Mortality in Incident Hemodialysis Patients

BACKGROUND

Higher serum ferritin levels may be influenced by iron use and inflammation, and are associated with higher mortality in hemodialysis (HD) patients. We hypothesized that a major rise in serum ferritin is associated with a higher risk of mortality, irrespective of baseline serum ferritin in incident HD patients.

METHODS

In a cohort of 93,979 incident HD patients between 2007 and 2011, we examined the association of change in serum ferritin from the baseline patient quarter (first 91 days from dialysis start) to the subsequent quarter with mortality. Multivariable adjustments were done for case-mix and markers of the malnutrition, and inflammation complex and intravenous iron dose. Change in serum ferritin was stratified into 5 groups: <-400, -400 to <-100, -100 to <100, 100 to <400, and ≥400 ng/mL/quarter.

RESULTS

The median change in serum ferritin was 89 ng/mL/quarter (interquartile range -55 to 266 ng/mL/quarter). Compared to stable serum ferritin (-100 to <100 ng/mL/quarter), a major rise (≥400 ng/mL/quarter) was associated with higher all-cause mortality (hazard ratio [95% CI] 1.07 [0.99-1.15], 1.17 [1.09-1.24], 1.26 [1.12-1.41], and 1.49 [1.27-1.76] according to baseline serum ferritin: <200, 200 to <500, 500 to <800, and ≥800 ng/mL in adjusted models, respectively. The mortality risk associated with a rise in serum ferritin was robust, irrespective of intravenous iron use.

CONCLUSIONS

During the first 6-months after HD initiation, a major rise in serum ferritin in those with a baseline ferritin ≥200 ng/mL and even a slight rise in serum ferritin in those with a baseline ferritin ≥800 ng/mL are associated with higher mortality.

Development and Validation of a Novel Laboratory-Specific Correction Equation for Total Serum Calcium and Its Association With Mortality Among Hemodialysis Patients

Conventional albumin-corrected calcium is inaccurate in predicting ionized calcium, and hidden hypercalcemia, characterized as high ionized calcium with normal total calcium, is associated with higher mortality in hemodialysis patients. By using a national cohort of hemodialysis patients in the Unites States, a novel laboratory-specific prediction equation composed of total calcium, albumin, and phosphorus was derived from 242 patients in the South Atlantic division (adjusted R2  = 0.80 versus 0.71 for the conventional equation) and then validated among 566 patients in the other divisions (adjusted R2  = 0.79 versus 0.68 for the conventional equation). Compared with the conventional equation, the novel equation showed a greater correlation with intact parathyroid hormone. Its relative performance against the conventional equation was consistent across subgroups based on medications related to calcium metabolism. The novel equation also had a higher sensitivity (57% versus 34%) and an equivalent specificity (99% versus 100%) against ionized hypercalcemia at a cut-off value of 10.2 mg/dL. Sensitivity and specificity at 9.4 mg/dL was 94% and 76% (versus 87% and 82% for the conventional equation), respectively. A survival analysis in 87,779 incident hemodialysis patients showed that among patients who were categorized as having a high-normal calcium status (ie, >9.4 to 10.2 mg/dL) by the conventional equation, there appeared a trend toward higher adjusted mortality risk across higher calcium status defined according to the novel equation. Meanwhile, the mortality risk was consistent across calcium strata defined according to the conventional equation within the categories defined by the novel equation. In conclusion, in comparison to the conventional equation, a novel laboratory-specific correction equation derived for correction of total calcium performs significantly better in ascertaining hidden hypercalcemia in hemodialysis patients, and aids in identifying patients at higher risk for mortality. © 2016 American Society for Bone and Mineral Research.