Association of markers of iron stores with outcomes in patients with nondialysis-dependent chronic kidney disease

Associations between iron markers with hemoglobin and outcomes in peritoneal dialysis patients: results from the PDTAP study

Background and hypothesis

Iron metabolism markers, such as transferrin saturation (TSAT) and ferritin, are crucial in anemia management in patients with CKD and those undergoing dialysis, yet optimal levels remain unelucidated.

Methods

We conducted a prospective multicenter cohort study using data from the nationwide Peritoneal Dialysis Telemedicine-based Management Platform (PDTAP) to analyze TSAT, ferritin, and hemoglobin (Hb) levels, and their associations with mortality in the peritoneal dialysis (PD) population.

Results

Our study included 4429 PD patients, analyzing data through restricted cubic splines and Cox regression models, adjusted for multiple confounders. Non-linear associations between Hb levels and TSAT/ferritin were observed. Hb levels increased with TSAT up to 40%, then plateaued, whereas ferritin levels increased with the decline of Hb. Further, ferritin levels above 200 ng/mL were independently linked to increased mortality risk [hazard ratio (HR) 1.207, 95% confidence interval (CI) 1.134-1.286], with this effect decreasing as high-sensitivity C-reactive protein levels rose. This risk was notably significant in patients with a history of cardiovascular disease. A ferritin/Hb ratio >2 was associated with increased risk of mortality after adjusting for demographic, nutritional factors and erythropoiesis agents (HR 1.219, 95% CI 1.144-1.299). The ferritin/Hb ratio demonstrated superior predictive ability for iron responsiveness compared with ferritin alone.

Conclusion

Serum ferritin level exceeding 200 ng/mL was indepently associated with a higher risk of martality in Chinese PD population. Monitoring the ferritin/Hb ratio may help assess the relative iron content in the body and provide reference for iron supplementation among patients undergoing PD.

The association between transferrin saturation and all-cause mortality in chronic kidney disease: findings from Korean Cohort Study for Outcome in Patients with Chronic Kidney Disease

BACKGROUND

Transferrin saturation (TSAT) has been used as an indicator of iron deficiency. However, there is no consensus regarding its optimal range for patient with chronic kidney disease (CKD). We aimed to analyze the effect of TSAT on the prognosis of patients with non-dialysis CKD (NDCKD).

METHODS

From 2011 to 2016, 2157 NDCKD patients with baseline TSAT measurements were followed for 10 years. Patients were divided into three groups based on baseline TSAT values: <25%, ≥25% and <45%, and ≥45%. All-cause mortality and 4-point major adverse cardiovascular events (MACE) were analyzed using multivariable Cox regression analysis. Other iron biomarkers and mortality were also analyzed.

RESULTS

During a mean follow-up of 7.1 ± 2.9 years, 182 of a total of 2,157 patients (8.4%) died. Compared with the TSAT ≥25% and <45% group, the TSAT <25% group showed significantly increased all-cause mortality (hazard ratio [HR], 1.44; 95% confidence interval (CI), 1.02-2.03; p = 0.04). The occurrence of 4-point MACE was significantly increased in univariable analysis in the TSAT <25% group (HR, 1.48; 95% CI, 1.02-2.15; p = 0.04), but it was not significant in the multivariable analysis (HR, 1.38; 95% CI, 0.89-2.15; p = 0.15). Tertile comparisons of the iron-to-log-ferritin ratio showed increased mortality in the first tertile group.

CONCLUSION

TSAT <25% is an independent risk factor for all-cause mortality in patients with NDCKD and care should be taken to prevent TSAT values of <25%. Other indicators, such as serum iron and iron-to-log-ferritin ratio, may also be used to assess iron deficiency.

Association of oral iron replacement therapy with kidney failure and mortality in CKD patients

Background

Oral iron is the predominant route of iron replacement (IRT) but its benefits and safety are unclear in patients with chronic kidney disease (CKD).

Methods

We examined the association of oral IRT vs no IRT with end-stage kidney disease (ESKD) and mortality in a national cohort of US Veterans. We identified 17 413 incident new users of oral IRT with estimated glomerular filtration rates <60 mL/min/1.73 m2 and 32 530 controls who did not receive any IRT during 2004-18. We used propensity score-overlap weighting to account for differences in key baseline characteristics associated with the use of oral IRT. We examined associations using competing risk regression and Cox models.

Results

In the cohort of 49 943 patients, 1616 (3.2%) patients experienced ESKD and 28 711 (57%) patients died during a median follow-up of 1.9 years. Oral IRT was not associated with ESKD [subhazard ratio (HR) (95% confidence interval, CI) 1.00 (0.84-1.19), P = .9] and was associated with higher risk of all-cause mortality [HR (95% CI) 1.06 (1.01-1.11), P = .01]. There was significant heterogeneity of treatment effect for mortality, with oral IRT associated with higher mortality in the subgroups of patients without congestive heart failure (CHF), anemia or iron deficiency. In patient with blood hemoglobin <10 g/dL oral IRT was associated with significantly lower mortality.

Conclusion

Oral IRT was associated with lower mortality only in patients with anemia. In patients without anemia, iron deficiency or CHF, the risk-benefit ratio of oral IRT should be further examined.

Association between iron status markers and kidney outcome in patients with chronic kidney disease

Several studies conducted in patients with various stages of chronic kidney disease (CKD) have investigated the association of iron status markers, such as transferrin saturation (TSAT) and serum ferritin, with kidney outcomes. However, the associations were inconsistent and remain strongly debated. Therefore, we aimed to investigate whether TSAT and serum ferritin levels were associated with kidney outcome in such a population. In this study, 890 patients who were admitted for the evaluation of and education for CKD were prospectively followed. Primary kidney outcome was a composite of doubling of serum creatinine, end-stage kidney disease, or death due to kidney failure. Participants were divided into quartiles (Q1-Q4) according to TSAT or serum ferritin levels. During a median follow-up period of 2.8 years, kidney events occurred in 358 patients. In the multivariable Cox analyses, compared with Q3 of TSAT, the hazard ratios (95% confidence intervals) for Q1, Q2, and Q4 were 1.20 (0.87, 1.66), 1.38 (1.01, 1.87), and 1.14 (0.82, 1.59), respectively. Compared with Q2 of serum ferritin, lower and higher quartiles had a significantly increased risk for kidney outcome; hazard ratios (95% confidence intervals) for Q1, Q3, and Q4 were 1.64 (1.18, 2.27), 1.71 (1.24, 2.37), and 1.52 (1.10, 2.10), respectively. A Fine-Gray model with death before kidney events as a competing risk showed results similar to the above. In CKD, lower and higher ferritin levels were independent risk factors for kidney disease progression.

The Association between Iron Deficiency and Renal Outcomes Is Modified by Sex and Anemia in Patients with Chronic Kidney Disease Stage 1–4

Iron deficiency is prevalent in women and patients with chronic kidney disease (CKD). Iron deficiency is not only related to anemia but contributes to adverse consequences for the kidney as well. Whether iron status is associated with renal outcomes after considering sex and anemia in patients with CKD stage 1–4 is unclear. Thus, we investigated the association of iron or iron saturation with renal outcomes in a CKD cohort. During a follow-up of 8.2 years, 781 (31.2%) patients met the composite renal outcome of renal replacement therapy and a 50% decline in renal function. In linear regression, iron was associated with sex, hemoglobin (Hb), and nutritional markers. In a fully adjusted Cox regression model, the male patients with normal iron had a significantly decreased risk of renal outcomes (hazard ratio (HR) 0.718; 95% confidence interval (CI) 0.579 to 0.889), but the female patients did not exhibit this association. The non-anemic patients (Hb ≥ 11 g/dL) had a decreased risk of renal outcomes (HR 0.715; 95% CI 0.568 to 0.898), but the anemic patients did not. In the sensitivity analysis, transferrin saturation (TSAT) showed similar results. When comparing iron and TSAT, both indicators showed similar prognostic values. In conclusion, iron deficiency, indicated by either iron or iron saturation, was associated with poor renal outcomes in the male or non-anemic patients with CKD stage 1–4.

Impact of iron status on kidney outcomes in kidney transplant recipients

Iron plays an important role in hemodynamics and the immunity, independent of anemia. Since dynamic changes occur in iron storage after kidney transplantation (KT), we investigated the association between iron status and kidney outcomes in KT patients. We analyzed data from the KoreaN cohort study for Outcome in patients With KT (KNOW-KT). The iron status was classified into three groups based on ferritin or transferrin saturation (TSAT) levels one year after KT, with reference ranges of 20‒35% and 100‒300 ng/mL for TSAT and ferritin, respectively. The primary outcome was the composite outcome, which consisted of death, graft failure, and an estimated glomerular filtration rate decline ≥ 50%. In total, 895 patients were included in the final analysis. During a median follow-up of 5.8 years, the primary outcome occurred in 94 patients (19.8/1000 person-years). TSAT levels decreased one year after KT and thereafter gradually increased, whereas ferritin levels were maintained at decreased levels. The adjusted hazard ratios (95% confidence intervals) for the composite outcome were 1.67 (1.00-2.77) and 1.20 (0.60-2.40) in the TSAT > 35% and ferritin > 300 ng/mL groups, respectively. High iron status with high TSAT levels increases the risk of graft failure or kidney functional deterioration after KT.

[Management of iron deficiency in chronic kidney disease: Review and proposed algorithm]

Iron deficiency is very common in chronic kidney disease, even before the dialysis stage. It is an independent factor of morbidity and mortality in patients with non-dialysis chronic kidney disease. During chronic kidney disease, iron deficiency is defined by a transferrin saturation <20% and/or a serum ferritin <100 μg/L. In France, about half of non-dialysis chronic kidney disease patients have absolute iron deficiency (transferrin saturation <20% and serum ferritin <100 μg/L) and/or functional iron deficiency (transferrin saturation <20% and serum ferritin >100 μg/L). Despite this, iron deficiency is usually not investigated. In fact, more than 60% of nephrologists do not assess iron status at least once a year. In addition, iron deficiency is rarely treated: only 12% of patients are prescribed oral or intravenous iron. Early detection and treatment are fundamental and should be systematic. In order to help improve the management of iron deficiency among non-dialysis chronic kidney disease patients, we propose an algorithm that takes into account current recommendations and the most recent data from the literature. Initial blood test requires the measurement of hemoglobin concentration, transferrin saturation and serum ferritin. A transferrin saturation <20% establishes the diagnosis of iron deficiency and the serum ferritin level points towards an absolute or functional deficiency. The combination of both values makes it possible to adapt the treatment, particularly in an inflammatory context where oral iron is not effective.

[Prevalence of iron deficiency in patients with non-dialysis chronic kidney disease: The CARENFER national, multicentre, observational study]

INTRODUCTION

Iron deficiency is common and associated with worse outcomes in patients with non-dialysis chronic kidney disease. We performed a national, multicentre, observational and transversal study to assess the prevalence of iron deficiency as well as current iron deficiency screening practices in this population.

PATIENTS AND METHODS

A total of 25 nephrology centres in France participated in the study. All adult non-dialysis chronic kidney disease patients who met the inclusion (GFR>15mL/min/1.73m²) and exclusion criteria and provided consent were systematically recruited over a 4-week inclusion period. Investigators were asked to perform a blood test (hemoglobin concentration, serum iron, serum ferritin and transferrin saturation) and to complete a questionnaire about their iron status monitoring practices. The primary objective was to assess the prevalence of iron deficiency (serum ferritin<100μg/L and/or transferrin saturation<20%). Secondary objectives were to evaluate the prevalence of absolute iron deficiency (serum ferritin<100μg/L and transferrin saturation<20%) and functional iron deficiency (serum ferritin≥100μg/L and transferrin saturation<20%), the prevalence of iron deficiency according to haemoglobin concentration and chronic kidney disease stage, the proportion of centres that perform routine evaluation of iron status and the number of patients receiving iron supplementation.

RESULTS

A total of 1211 patients with non-dialysis chronic kidney disease were included in the analysis. The overall prevalence of iron deficiency was 47.1%. The rates of absolute iron deficiency and functional iron deficiency and anaemia were 13.4% and 17.1%, respectively. Among the 25 participating centres, 12 reported routine assessment of iron status in non-dialysis chronic kidney disease patients.

CONCLUSION

In this observational study, a high prevalence of iron deficiency was observed among non-dialysis chronic kidney disease patients. Less than half of participating centres reported routine assessment of iron status.

Protein Energy Wasting in a Cohort of Maintenance Hemodialysis Patients in Dhaka, Bangladesh

Malnutrition is associated with high rates of mortality among patients with end stage kidney disease (ESKD). There is a paucity of data from Bangladesh, where around 35,000−40,000 people reach ESKD annually. We assessed protein-energy wasting (PEW) amongst 133 patients at a single hemodialysis setting in Dhaka. Patients were 49% male, age 50 ± 13 years, 62% were on twice-weekly hemodialysis. Anthropometric, biochemical, and laboratory evaluations revealed: BMI 24.1 ± 5.2 kg/m2, mid-arm muscle circumference (MAMC) 21.6 ± 3.6 cm, and serum albumin 3.7 ± 0.6 g/dL. Based on published criteria, 18% patients had PEW and for these patients, BMI (19.8 ± 2.4 vs. 25.2 ± 5.2 kg/m2), MAMC (19.4 ± 2.4 vs. 22.2 ± 3.8 cm), serum albumin (3.5 ± 0.7 vs. 3.8 ± 0.5 g/dL), and total cholesterol (135 ± 34 vs. 159 ± 40 mg/dL), were significantly lower as compared to non-PEW patients, while hand grip strength was similar (19.5 ± 7.6 vs. 19.7 ± 7.3 kg). Inflammatory C-reactive protein levels tended to be higher in the PEW group (20.0 ± 34.8 vs. 10.0 ± 13.9 p = 0.065). Lipoprotein analyses revealed PEW patients had significantly lower low density lipoprotein cholesterol (71 ± 29 vs. 88 ± 31 mg/dL, p < 0.05) and plasma triglyceride (132 ± 51 vs. 189 ± 103 mg/dL, p < 0.05), while high density lipoprotein cholesterol was similar. Nutritional assessments using a single 24 h recall were possible from 115 of the patients, but only 66 of these were acceptable reporters. Amongst these, while no major differences were noted between PEW and non-PEW patients, the majority of patients did not meet dietary recommendations for energy, protein, fiber, and several micronutrients (in some cases intakes were 60−90% below recommendations). Malnutrition Inflammation Scores were significantly higher in PEW patients (7.6 ± 3.1 vs. 5.3 ± 2.7 p < 0.004). No discernible differences were apparent in measured parameters between patients on twice- vs. thrice-weekly dialysis. Data from a larger cohort are needed prior to establishing patient-management guidelines for PEW in this population.

Serum Biomarkers of Iron Stores Are Associated with Increased Risk of All-Cause Mortality and Cardiovascular Events in Nondialysis CKD Patients, with or without Anemia

BACKGROUND

Approximately 30%-45% of patients with nondialysis CKD have iron deficiency. Iron therapy in CKD has focused primarily on supporting erythropoiesis. In patients with or without anemia, there has not been a comprehensive approach to estimating the association between serum biomarkers of iron stores, and mortality and cardiovascular event risks.

METHODS

The study included 5145 patients from Brazil, France, the United States, and Germany enrolled in the Chronic Kidney Disease Outcomes and Practice Patterns Study, with first available transferrin saturation (TSAT) and ferritin levels as exposure variables. We used Cox models to estimate hazard ratios (HRs) for all-cause mortality and major adverse cardiovascular events (MACE), with progressive adjustment for potentially confounding variables. We also used linear spline models to further evaluate functional forms of the exposure-outcome associations.

RESULTS

Compared with patients with a TSAT of 26%-35%, those with a TSAT ≤15% had the highest adjusted risks for all-cause mortality and MACE. Spline analysis found the lowest risk at TSAT 40% for all-cause mortality and MACE. Risk of all-cause mortality, but not MACE, was also elevated at TSAT ≥46%. Effect estimates were similar after adjustment for hemoglobin. For ferritin, no directional associations were apparent, except for elevated all-cause mortality at ferritin ≥300 ng/ml.

CONCLUSIONS

Iron deficiency, as captured by TSAT, is associated with higher risk of all-cause mortality and MACE in patients with nondialysis CKD, with or without anemia. Interventional studies evaluating the effect on clinical outcomes of iron supplementation and therapies for alternative targets are needed to better inform strategies for administering exogenous iron.

Heart Failure Hospitalization Risk associated with Iron Status in Veterans with CKD

BACKGROUND AND OBJECTIVES

CKD is an independent risk factor for heart failure. Iron dysmetabolism potentially contributes to heart failure, but this relationship has not been well characterized in CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed a historical cohort study using data from the Veterans Affairs Corporate Data Warehouse to evaluate the relationship between iron status and heart failure hospitalization. We identified a CKD cohort with at least one set of iron indices between 2006 and 2015. The first available date of serum iron indices was identified as the study index date. The cohort was divided into four iron groups on the basis of the joint quartiles of serum transferrin saturation (shown in percent) and ferritin (shown in nanograms per milliliter): reference (16%-28%, 55-205 ng/ml), low iron (0.4%-16%, 0.9-55 ng/ml), high iron (28%-99.5%, 205-4941 ng/ml), and function iron deficiency (0.8%-16%, 109-2783 ng/ml). We compared 1-year heart failure hospitalization risk between the iron groups using matching weights derived from multinomial propensity score models and Poisson rate-based regression.

RESULTS

A total of 78,551 veterans met the eligibility criteria. The covariates were well balanced among the iron groups after applying the propensity score weights (n=31,819). One-year adjusted relative rate for heart failure hospitalization in the iron deficiency groups were higher compared with the reference group (low iron: 1.29 [95% confidence interval, 1.19 to 1.41]; functional iron deficiency: 1.25 [95% confidence interval, 1.13 to 1.37]). The high-iron group was associated with lower 1-year relative rate of heart failure hospitalization (0.82; 95% confidence interval, 0.72 to 0.92). Furthermore, the association between iron deficiency and heart failure hospitalization risk remained consistent regardless of the diabetes status or heart failure history at baseline.

CONCLUSIONS

Iron deficiency, regardless of cause, was associated with higher heart failure hospitalization risk in CKD. Higher iron status was associated with lower heart failure hospitalization risks.

Intact and C-Terminal FGF23 Assays-Do Kidney Function, Inflammation, and Low Iron Influence Relationships With Outcomes?

CONTEXT

Higher fibroblast growth factor-23 (FGF23) concentrations are associated with heart failure and mortality in diverse populations, but the strengths of associations differ markedly depending up on which assay is used.

OBJECTIVE

We sought to evaluate whether iron deficiency, inflammation, or kidney function account for differences in the strengths of associations between these 2 FGF23 assays with clinical outcomes.

DESIGN

Case cohort study from the Cardiovascular Health Study.

SETTING

A total of 844 community-dwelling individuals aged 65 years or older with and without chronic kidney disease were followed for 10 years.

OUTCOMES

Outcomes included death, incident heart failure (HF), and incident myocardial infarction (MI). Exposure was baseline intact and C-terminal FGF23. Using modified Cox models, adjusting sequentially we tested whether observed associations of each assay with outcomes were attenuated by iron status, inflammation, kidney function, or their combinations.

RESULTS

FGF23 measured by either assay was associated with mortality in unadjusted analysis (intact FGF23 hazard ratio [HR] per 2-fold higher 1.45; 95% CI, 1.25-1.68; C-terminal FGF23 HR 1.38; 95% CI, 1.26-1.50). Adjustment for kidney function completely attenuated associations of intact FGF23 with mortality (HR 1.00; 95% CI, 0.85-1.17), but had much less influence on the association of C-terminal FGF23, for which results remained significant after adjustment (HR 1.15; 95% CI, 1.04-1.28). Attenuation was much less with adjustment for iron status or inflammation. Results were similar for the HF end point. Neither C-terminal or intact FGF23 was associated with MI risk.

CONCLUSIONS

The relationship of FGF23 with clinical end points is markedly different depending on the type of FGF23 assay used. The associations of biologically active FGF23 with clinical end points may be confounded by kidney disease, and thus much weaker than previously thought.

FGF23 and Cause-Specific Mortality in Community-Living Individuals-The Health, Aging, and Body Composition Study

OBJECTIVES

Fibroblast growth factor (FGF)-23 is a key regulator of mineral metabolism and has been linked with left ventricular hypertrophy in animal models. Most existing epidemiologic studies evaluated a C-terminal FGF23 assay which measures both the intact (active) hormone and inactive fragments. The relationship of intact FGF23 with cause-specific mortality is unknown.

DESIGN

Prospective analyses of data from Health, Aging, & Body Composition (HABC) study.

SETTING

Community-living adults aged 70 to 79 years with longitudinal follow up.

Systemic inflammation modulates the ability of serum ferritin to predict all-cause and cardiovascular mortality in peritoneal dialysis patients

BACKGROUND

This study aimed to ascertain whether the correlation of high serum ferritin with mortality is affected by systemic inflammation and to investigate the optimal serum ferritin level for predicting death when inflammation is considered in peritoneal dialysis (PD) patients.

METHODS

We classified 221 patients into four groups according to serum ferritin concentration (100 μg/L) and high-sensitivity CRP (hs-CRP) level (3 mg/L), and followed them regularly from the date of catheterization to Dec 31, 2016, at Sun Yat-Sen Memorial Hospital, China. Clinical and biochemical data were collected at baseline, and clinical outcomes such as all-cause and cardiovascular mortality were assessed.

RESULTS

During a median follow-up of 35 months (3 ~ 109 months), 50 (22.6%) deaths occurred. Cardiovascular disease (46.0%) was the most common cause of death, followed by infection (10.0%). The Kaplan-Meier survival analysis and log-rank test revealed significantly worse survival accumulation among PD patients with higher serum ferritin (≥100 μg/L) under elevated hsCRP levels (> 3 mg/L) (P = 0.022). A multivariate Cox regression analysis revealed that an increased serum ferritin level was independently associated with a higher risk of all-cause and cardiovascular mortality in PD patients (HR = 3.114, P = 0.021; and HR = 9.382, P = 0.032) with hsCRP above 3 mg/L after adjusting for relevant confounding factors.

CONCLUSION

Higher serum ferritin levels were associated with an increased risk of all-cause and cardiovascular mortality in patients undergoing PD only in the presence of elevated hsCRP levels. The correlation of serum ferritin with poor outcome should take into consideration systemic inflammation.

Prevalence, correlates and outcomes of absolute and functional iron deficiency anemia in nondialysis-dependent chronic kidney disease

Background

Anemia is associated with adverse outcomes in those with chronic kidney disease (CKD). We examined the association of absolute and functional iron deficiency anemia (IDA) with adverse outcomes (cardiovascular hospitalization, dialysis and mortality) in those with nondialysis-dependent CKD.

Methods

Nondialysis-dependent CKD patients followed in the US Veterans Administration with hemoglobin level measured within 90 days of the date of the second estimated glomerular filtration rate &lt;60 mL/min/1.73 m2 were included. Logistic regression, multivariate Cox proportional hazards and Poisson regression models adjusted for demographics and comorbidities were used to assess the prevalence and correlates of absolute [transferrin saturation (TSAT) ≤20%, ferritin &lt;100 ng/mL] and functional (TSA T≤20%, ferritin &gt;100–500 ng/mL) IDA and the associations of absolute and functional IDA with mortality, dialysis and cardiovascular hospitalization.

Results

Of 933 463 patients with CKD, 20.6% had anemia. Among those with anemia, 23.6% of patients had both TSAT and ferritin level measured, of whom 30% had absolute IDA and 19% had functional IDA. Absolute IDA in CKD was not associated with an increased risk of mortality or dialysis but was associated with a higher risk of 1-year {risk ratio [RR] 1.20 [95% confidence interval (CI) 1.12–1.28]} and 2-year cardiovascular hospitalization [RR 1.11 (95% CI 1.05–1.17)]. CKD patients with functional IDA had a higher risk of mortality [hazard ratio (HR) 1.11 (95% CI 1.07–1.14)] along with a higher risk of 1-year [RR 1.21 (95% CI 1.1–1.30)] and 2-year cardiovascular hospitalization [RR 1.13 (95% CI 1.07–1.21)]. Ferritin &gt;500 ng/mL (treated as a separate category) was only associated with an increased risk of mortality [HR 1.38 (95% CI 1.26–1.51)].

Conclusions

In a large population of CKD patients with anemia, absolute and functional IDA were associated with various clinical covariates. Functional IDA was associated with an increased risk of mortality and cardiovascular hospitalization, but absolute IDA was associated only with a higher risk of hospitalization.

Impact of Inflammation on Ferritin, Hepcidin and the Management of Iron Deficiency Anemia in Chronic Kidney Disease

Iron deficiency anemia (IDA) is a major problem in chronic kidney disease (CKD), causing increased mortality. Ferritin stores iron, representing iron status. Hepcidin binds to ferroportin, thereby inhibiting iron absorption/efflux. Inflammation in CKD increases ferritin and hepcidin independent of iron status, which reduce iron availability. While intravenous iron therapy (IIT) is superior to oral iron therapy (OIT) in CKD patients with inflammation, OIT is as effective as IIT in those without. Inflammation reduces predictive values of ferritin and hepcidin for iron status and responsiveness to iron therapy. Upper limit of ferritin to predict iron overload is higher in CKD patients with inflammation than in those without. However, magnetic resonance imaging studies show lower cutoff levels of serum ferritin to predict iron overload in dialysis patients with apparent inflammation than upper limit of ferritin proposed by international guidelines. Compared to CKD patients with inflammation, optimal ferritin levels for IDA are lower in those without, requiring reduced iron dose and leading to decreased mortality. The management of IDA should differ between CKD patients with and without inflammation and include minimization of inflammation. Further studies are needed to determine the impact of inflammation on ferritin, hepcidin and therapeutic strategy for IDA in CKD.

Optimal Serum Ferritin Levels for Iron Deficiency Anemia during Oral Iron Therapy (OIT) in Japanese Hemodialysis Patients with Minor Inflammation and Benefit of Intravenous Iron Therapy for OIT-Nonresponders

Background: We determined optimal serum ferritin for oral iron therapy (OIT) in hemodialysis (HD) patients with iron deficiency anemia (IDA)/minor inflammation, and benefit of intravenous iron therapy (IIT) for OIT-nonresponders. Methods: Inclusion criteria were IDA (Hb <120 g/L, serum ferritin <227.4 pmol/L). Exclusion criteria were inflammation (C-reactive protein (CRP) ≥ 5 mg/L), bleeding, or cancer. IIT was withheld >3 months before the study. ΔHb ≥ 20 g/L above baseline or maintaining target Hb (tHB; 120-130 g/L) was considered responsive. Fifty-one patients received OIT (ferrous fumarate, 50 mg/day) for 3 months; this continued in OIT-responders but was switched to IIT (saccharated ferric oxide, 40 mg/week) in OIT-nonresponders for 4 months. All received continuous erythropoietin receptor activator (CERA). Hb, ferritin, hepcidin-25, and CERA dose were measured. Results: Demographics before OIT were similar between OIT-responders and OIT-nonresponders except low Hb and high triglycerides in OIT-nonresponders. Thirty-nine were OIT-responders with reduced CERA dose. Hb rose with a peak at 5 months. Ferritin and hepcidin-25 continuously increased. Hb positively correlated with ferritin in OIT-responders (r = 0.913, p = 0.03) till 5 months after OIT. The correlation equation estimated optimal ferritin of 30-40 ng/mL using tHb (120-130 g/L). Seven OIT-nonresponders were IIT-responders. Conclusions: Optimal serum ferritin for OIT is 67.4-89.9 pmol/L in HD patients with IDA/minor inflammation. IIT may be a second line of treatment for OIT-nonreponders.

Association between Serum Ferritin and Contrast-Induced Nephropathy in Patients with Acute Coronary Syndrome Undergoing Percutaneous Coronary Intervention

Background and Aims. CIN is a major and serious complication following PCI in patients with ACS. It is unclear whether a higher serum ferritin level is associated with an increased risk of CIN in high-risk patients. Thus, we conducted this study to assess the predictive value of SF for the risk of CIN after PCI. Methods. We prospectively examined SF levels in 548 patients with ACS before undergoing PCI. Multivariate logistic regression analysis was used to analyze the independent risk factors for CIN. The ROC analysis was performed to evaluate the predictive value of SF for CIN. Results. CIN occurred in 96 patients. Baseline SF was higher in patients who developed CIN compared to those who did not (257.05 ± 93.98 versus 211.67 ± 106.65; P < 0.001). Multivariate logistic regression analysis showed that SF was an independent predictor of CIN (OR, 1.008; 95% CI, 1.003–1.013; P = 0.002). The area under ROC curve for SF was 0.629, and SF > 180.9 μg/L predicted CIN with sensitivity of 80.2% and specificity of 41.4%. Conclusion. Our data show that a higher SF level was significantly associated with an increased risk of CIN after PCI.

Anaemia management and mortality risk in newly visiting patients with chronic kidney disease in Japan: The CKD-ROUTE study

AIM

To investigate the association between iron deficiency anaemia and mortality risk and assess the changes in anaemia and iron status after primary management by a nephrologist.

METHODS

In this prospective cohort study, we stratified 951 non-dialysis chronic kidney disease (CKD) G2-G5 patients newly visiting 16 nephrology centres into four groups according to the presence of anaemia with or without iron deficiency. All-cause mortality, cardiovascular (CV)-related mortality, and a change in anaemia and iron status after specialized primary care were the endpoints evaluated.

RESULTS

During a median follow-up time of 19 months, the number of all-cause deaths and CV-related deaths were 56 and 26, respectively. Compared with the control group, the groups with isolated anaemia and iron deficiency anaemia had significantly higher all-cause mortalities (isolated anaemia: hazard ratio (HR), 3.37; 95% confidence intervals (CI), 1.76-6.44; iron deficiency anaemia: HR, 3.11; 95% CI, 1.21-8.01) and CV-related mortalities (isolated anaemia: HR, 3.64; 95% CI, 1.36-9.73; iron deficiency anaemia: HR, 3.86; 95% CI, 1.11-13.41). In the isolated anaemia group, erythropoietin-stimulating agent (ESA) prescriptions significantly increased to approximately 70%. However, in patients with both anaemia and iron deficiency, iron prescriptions only increased to 48.1%.

CONCLUSIONS

Iron deficiency anaemia and isolated anaemia were associated with all-cause and CV-related mortality. The absence of relative increase in iron prescriptions suggests that iron deficiency should be accurately assessed and iron supplementation should be appropriately used to manage anaemia in non-dialysis patients with CKD.

Safety concerns about intravenous iron therapy in patients with chronic kidney disease

Anaemia in chronic kidney disease (CKD) is managed primarily with erythropoiesis-stimulating agents (ESAs) and iron therapy. Following concerns around ESA therapy, intravenous (IV) iron is being administered more and more worldwide. However, it is still unclear whether this approach is safe at very high doses or in the presence of very high ferritin levels. Some observational studies have shown a relationship between either high ferritin level or high iron dose and increased risk of death, cardiovascular events, hospitalization or infection. Others have not been able to confirm these findings. However, they suffer from indication biases. On the other hand, the majority of randomized clinical trials have only a very short follow-up (and thus drug exposure) and are inadequate to assess the mortality risk. None of them have tested the role of different iron doses on hard end points. With the lack of clear evidence coming from well-designed and large-scale studies, several data suggest that excessive iron therapy may be toxic in several aspects, ranging from iron overload to tissue damage from labile iron. A number of experimental and clinical data suggest that either excessive iron therapy or iron overload may be a possible culprit of atherogenesis. The process seems to be mediated by oxidative stress. Iron therapy should also be used cautiously in the presence of active infections, since iron is essential for bacterial growth. Recently, the European Medicines Agency officially raised concerns about rare hypersensitivity reactions following IV iron administration. The balance has been in favour of benefits. In several European countries, this has created a lot of confusion and somewhat slowed the run towards excessive use. Altogether, IV iron remains a mainstay of anaemia treatment in CKD patients. However, in our opinion, its excessive use should be avoided, especially in patients with high ferritin levels and when ESA agents are not contraindicated.

Lipids, blood pressure and kidney update 2015

The most important studies and guidelines in the topics of lipid, blood pressure and kidney published in 2015 were reviewed. In lipid research, the IMProved Reduction of Outcomes: Vytorin Efficacy International Trial (IMPROVE-IT) trial revalidated the concept "lower is better" for low density lipoprotein (LDL)-cholesterol as a target for therapy, increasing the necessity of treatment the high-risk patients to achieve LDL-C goals. After these results, ezetimibe might become the preferred additional drug in the combination therapy of lipid disorders because of oral dosage form and lower acquisition cost. However, for the statin-intolerant patients and those patients requiring essential reductions in LDL-C to achieve their goals, new therapies, including PCSK9 inhibitors remain promising drugs. In blood pressure research, American Heart Association (AHA)/American College of Cardiology (ACC) 2015 guidelines recommended a target for blood pressure below 140/90 mmHg in stable or unstable coronary artery disease patients and below 150/90 mmHg in patients older than 80 years of age, however the recent results of the Systolic Blood Pressure Intervention Trial (SPRINT) trial have suggested that there might be significant benefits, taking into account cardiovascular risk, for hypertensive patients over 50 without diabetes and blood pressure levels <120/80. In kidney research, reducing the progression of chronic kidney disease and related complications such as anemia, metabolic acidosis, bone and mineral diseases, acute kidney injury and cardiovascular disease is still a goal for clinicians.

Guidelines on the diagnosis and treatment of iron deficiency across indications: a systematic review

BACKGROUND

Guidelines on the diagnosis and treatment of iron deficiency (ID) vary widely across indications.

OBJECTIVE

We reviewed all available guidelines on the management of ID worldwide.

DESIGN

A literature search was conducted in PubMed, Cochrane, and EMBASE and in main professional association websites, limited to documents published between 1 January 2004 and 30 June 2014.

RESULTS

Of 127 guidelines identified, 29 were selected, involving 29 professional associations and issued from the United States (n = 8), Europe (n = 6), Britain (n = 4), Canada (n = 3), international organizations (n = 2), France (n = 2), Poland (n = 1), Australia (n = 1), Mexico (n = 1), and Japan (n = 1). A total of 22 and 27 guidelines provided recommendations on diagnosis and treatment of ID, respectively. To define ID, all guidelines recommended a concentration for serum ferritin. One-half of them (10 of 22) proposed transferrin saturation (TSAT) as an alternative or complementary diagnostic test. To treat ID, most of the guidelines (18 of 27) recommended preferentially the oral route if possible, particularly in children and in women in the pre- or postpregnancy period. Iron supplementation should be administered intravenously according to 13 of 27 guidelines, particularly in patients with chronic kidney disease (CKD) (n = 7) and chemotherapy-induced anemia (n = 5). Treatment targets for ID included an increase in hemoglobin concentrations to 10-12 g/dL or normalization (n = 8) and serum ferritin >100 μg/L (n = 7) or 200 μg/L (n = 4). For the latter, in some situations, such as CKD, ferritin concentrations should not exceed 500 μg/L (n = 5) or 800 μg/L (n = 5). Only 9 guidelines recommended TSAT as a target, proposing various thresholds ranging from 20% to 50%.

CONCLUSIONS

It appears that for the diagnosis of ID, a cutoff of 100 μg/L for serum ferritin concentration should be considered in most conditions and 20% for TSAT, except in particular situations, including young healthy women with heavy menstrual flow. New indications of intravenous iron supplementation are emerging.

Iron supplementation associates with low mortality in pre-dialyzed advanced chronic kidney disease patients receiving erythropoiesis-stimulating agents: a nationwide database analysis

BACKGROUND

A risk/benefit analysis of iron supplementation in pre-dialysis advanced chronic kidney disease (CKD) patients has not been conducted. We aim to assess the effectiveness and the safety of iron supplementation in patients with CKD Stage 5 who have not yet received dialysis (CKD 5 ND).

METHODS

A prospective cohort study was conducted based on the Taiwan National Health Insurance Research Database. From 1 January 2000 to 30 June 2009, we enrolled 31 971 adult patients who had a serum creatinine >6 mg/dL and a haematocrit <28% and who were treated with erythropoiesis-stimulating agents (ESAs). All patients were further divided into two groups with or without iron supplementation within 90 days after starting ESA therapy. Patient follow-up took place until dialysis, death before initiation of dialysis or 31 December 2009. The primary outcomes were death before initiating dialysis, hospitalization before death or long-term dialysis.

RESULTS

After propensity score matching, the patients who received iron supplementation were associated with a lower risk of all-cause death [hazard ratio (HR), 0.85; 95% confidence interval (CI), 0.80-0.90] compared with non-users. The survival benefit of iron use was consistent across the majority of dosage groups, except for those who were treated with monthly IV iron >200 mg. Moreover, compared with the non-users, the iron users were associated with a lower risk of hospitalizations (HR, 0.97; 95% CI, 0.94-0.99) but with a higher risk of faster progression to end-stage renal disease (HR, 1.05; 95% CI, 1.01-1.08).

CONCLUSIONS

Iron supplementation is associated with 15% risk reduction in death among CKD 5 ND patients who received ESA treatment. Randomized studies are needed to validate this association.

Ferritin as a predictor of decline in residual renal function in peritoneal dialysis patients

AIMS

Inflammation is an important factor in renal injury. Ferritin, an inflammatory marker, is considered an independent predictor of rapid renal progression in patients with chronic kidney disease. However, the relationship between ferritin and residual renal function (RRF) in patients undergoing peritoneal dialysis (PD) remains unclear.

METHODS

We reviewed the medical records of patients who started PD between June 2001 and March 2012 at Soonchunhyang University Bucheon Hospital, Korea. A total of 123 patients were enrolled in the study. At 1 month after the initiation of PD, RRF was determined by a 24-hour urine collection and measured every 6 months thereafter. Clinical and biochemical data at the time of the initial 24-hour urine collection were considered as baseline.

RESULTS

The RRF reduction rate was significantly greater in patients with high ferritin (ferritin ≥ 250 ng/mL) compared with those with low ferritin (ferritin < 250 ng/mL; -1.71 ± 1.36 mL/min/yr/1.73 m(2) vs. -0.84 ± 1.63 mL/min/yr/1.73 m(2), respectively; p = 0.007). Pearson correlation analysis revealed a significant negative correlation between the baseline serum ferritin level and the RRF reduction rate (r = -0.219, p = 0.015). Using multiple linear regression analysis and adjusting for other risk factors, baseline serum ferritin was an independent factor for the RRF reduction rate (β = -0.002, p = 0.002).

CONCLUSIONS

In this study we showed that a higher ferritin level was significantly associated with a more rapid RRF decline in patients undergoing PD.

Kidney Disease: Improving Global Outcomes guidelines on anaemia management in chronic kidney disease: a European Renal Best Practice position statement

Recently, the Kidney Disease: Improving Global Outcomes (KDIGO) group has produced comprehensive clinical practice guidelines for the management of anaemia in CKD patients. These guidelines addressed all of the important points related to anaemia management in CKD patients, including therapy with erythropoieis stimulating agents (ESA), iron therapy, ESA resistance and blood transfusion use. Because most guidelines were 'soft' rather than 'strong', and because global guidelines need to be adapted and implemented into the regional context where they are used, on behalf of the European Renal Best Practice Advisory Board some of its members, and other external experts in this field, who were not participants in the KDIGO guidelines group, were invited to participate in this anaemia working group to examine and comment on the KDIGO documents in this position paper. In this article, the group concentrated only on those guidelines which we considered worth amending or adapting. All guidelines not specifically mentioned are fully endorsed.

Iron Indices in Patients with Functional Anemia in Chronic Kidney Disease

BACKGROUND

Despite high ferritin level, HDCKD patients may have functional iron deficiency even after intravenous iron (iv) therapy. The aim of this study was to test the hypothesis that lowered serum transferrin level may contribute to functional anemia and erythropoietin hypo responsiveness by the failure to transport accumulated tissue iron to the relevant target tissue.

MATERIALS AND METHODS

The study subjects were divided into four groups. Group-A: HDCKD Patients receiving iv iron (n=290). Group-B: Patients not initiated on to hemodialysis (NDCKD), and received oral iron (n=38). Group-C: HDCKD patients with erythropoietin hypo responsiveness (n=9). Group-D: Healthy controls (n=36). The group-A, patients were sub-divided into five groups (A-1 to A-5) based on their serum ferritin levels.

RESULTS

Serum ferritin and tissue iron levels in group-A and C patients were significantly greater than the group-D(p<0.0001) and group-B patients(p<0.001). Transferrin level of group-A and C showed lowered values and consequently a higher %TSAT when compared to group-D. The percent of patients with iron overload was 2.6%, 31%, and 44% in group-B, group-A and group-C respectively. Serum transferrin level significantly correlated with TIBC in group-A and B patients (p<0.0001;p<0.05 respectively). Transferrin level significantly correlated with TIBC in all subgroups of HDCKD(p<0.05) with the exception in subgroup-A2 and with hemoglobin in subgroups A3 (p<0.05) and A5(p<0.01) respectively.

CONCLUSIONS

The lowered transferrin level prevents the proper transport of the iron to the hematopoietic sites, which may be a reason for the low hemoglobin synthesis and also for the development of erythropoietin hypo responsiveness in some of the dialysis patients.

Association of hsCRP, white blood cell count and ferritin with renal outcome in chronic kidney disease patients

Inflammation is a pathogenic factor in renal injury, but whether inflammation is related to renal outcome in chronic kidney disease (CKD) patients is little known. We thus assess the association of inflammation and renal outcome in an advanced CKD cohort. This study analyzed the association between inflammatory markers, such as C-reactive protein (hsCRP), white blood cell (WBC) count and ferritin, renal replacement therapy (RRT) and rapid renal progression (estimated GFR slope<-6 ml/min/1.73 m²/y) in 3303 patients with stage 3–5 CKD. In all subjects, the mean hsCRP, WBC count, and ferritin levels were 1.2 (0.4, 5.4) mg/L, 7.2±2.3×10³ cells/µL, and 200 (107,349) ng/mL, respectively. During a mean 3.2-year follow-up, there were 1080 (32.7%) subjects commencing RRT, and 841(25.5%) subjects presenting rapid renal progression. Both hsCRP and ferritin were associated with increased risk for RRT with the adjusted HR (tertile 3 versus tertile 1∶1.17 〔1.01–1.36〕 and 1.20 〔1.03–1.40〕, respectively). Both hsCRP and ferritin were associated with increased odds for rapid renal progression with the adjusted OR (tertile 3 versus tertile 1∶1.40 〔1.13–1.77〕 and 1.32 〔1.06–1.67〕, respectively). hsCRP and ferritin stratified by albumin were also associated with RRT and rapid renal progression. Instead, WBC count was not associated with renal outcome. In conclusion, elevated levels of hsCRP and ferritin are risk factors associated with RRT and rapid renal progression in advanced CKD patients.

Disordered iron homeostasis in chronic heart failure: prevalence, predictors, and relation to anemia, exercise capacity, and survival

OBJECTIVES

The aim of this study was to comprehensively delineate iron metabolism and its implications in patients with chronic heart failure (CHF).

BACKGROUND

Iron deficiency is an emerging therapeutic target in CHF.

METHODS

Iron and clinical indexes were quantified in 157 patients with CHF.

RESULTS

Several observations were made. First, iron homeostasis was deranged in anemic and nonanemic subjects and characterized by diminished circulating (transferrin saturation) and functional (mean cell hemoglobin concentration) iron status in the face of seemingly adequate stores (ferritin). Second, while iron overload and elevated iron stores were rare (1%), iron deficiency (transferrin saturation <20%) was evident in 43% of patients. Third, disordered iron homeostasis related closely to worsening inflammation and disease severity and strongly predicted lower hemoglobin levels independently of age, sex, erythrocyte sedimentation rate, New York Heart Association (NYHA) functional class, and creatinine. Fourth, the etiologies of anemia varied with disease severity, with an iron-deficient substrate (anemia of chronic disease and/or iron-deficiency anemia) evident in 16%, 72%, and 100% of anemic NYHA functional class I or II, III, and IV patients, respectively. Although anemia of chronic disease was more prevalent than iron-deficiency anemia, both conditions coexisted in 17% of subjects. Fifth, iron deficiency was associated with lower peak oxygen consumption and higher ratios of ventilation to carbon dioxide production and identified those at enhanced risk for death (hazard ratio: 3.38; 95% confidence interval: 1.48 to 7.72; p = 0.004) independently of hemoglobin. Nonanemic iron-deficient patients had a 2-fold greater risk for death than anemic iron-replete subjects.

CONCLUSIONS

Disordered iron homeostasis in patients with CHF relates to impaired exercise capacity and survival and appears prognostically more ominous than anemia.

Correction of iron deficiency in the cardiorenal syndrome

Impaired energy metabolism is a feature of Congestive Heart Failure (CHF). Iron deficiency has been shown to reduce energy production in the cell in animals and humans. Iron deficiency is common in both Chronic Kidney Disease (CKD) and in CHF. Recent studies suggest that iron deficiency is an independent risk factor for mortality in CHF. Studies of correction of the anemia with intravenous (IV) iron in both CKD and CHF have shown an improvement in the anemia and, in some cases, in the renal function as well. Some CHF studies of correction of the iron deficiency have shown an improvement in cardiac function and structure as well as in exercise capacity and quality of life. This occurred independent of whether or not they had anemia, suggesting that the iron deficiency itself may be independently contributing to the worsening of the CHF and CKD. If future long-term studies confirm the safety and efficacy of IV iron in the treatment of iron deficiency in CKD and CHF, this will become a new addition to the therapeutic armamentarium of the cardiorenal syndrome, and parameters of iron deficiency will become part of the routine measurements performed in both CKD and CHF whether or not the patient is anemic.

Iron therapy in chronic kidney disease: current controversies

Anaemia in chronic kidney disease (CKD) is a complex disease that requires an integrated approach to incorporate both diagnostic and therapeutic interventions and to address the different facets of its aetiology and pathophysiology. The advent of erythropoiesis stimulating agents (ESA) has revolutionised the therapy of anaemia of CKD, and has resulted in a significant decline in the need for blood transfusions in CKD patients. The routine application of ESA has also led to the need for concomitant iron supplementation. ESA and iron therapy now form the cornerstone of anaemia management in CKD. Intravenous iron administration is effective with acceptable safety, and may improve ESA responsiveness. However, less is known about the long-term safety of iron supplementation in CKD patients. Whereas maintenance (weekly to monthly) intravenous iron has been routinely used in maintenance dialysis patients, iron replacement in patients with non-dialysis-dependent CKD is less well studied, in spite of the much larger number of patients affected. This review discusses iron supplementation in CKD with an emphasis toward controversial issues that continue to pose dilemmas in clinical practice. Concerns related to both the optimal amount of iron supplementation and to the safety of various agents available in clinical practice are presented.

Bone marrow iron, iron indices, and the response to intravenous iron in patients with non-dialysis-dependent CKD

BACKGROUND

Information about iron stores and their relationship with transferrin saturation (TSAT), serum ferritin, and the erythropoietic response to iron therapy is scarce in anemic non-dialysis-dependent patients with chronic kidney disease (CKD). We examined the diagnostic utility of peripheral-iron indices and the erythropoietic response to intravenous iron as indices of iron store depletion using bone marrow iron as a reference test in anemic non-dialysis-dependent patients with CKD.

STUDY DESIGN

Diagnostic test study.

SETTING & PARTICIPANTS

100 anemic (hemoglobin <11 g/dL) patients with CKD stages 3-5, not receiving epoetin and iron.

INDEX TESTS

TSAT index and serum ferritin level at baseline and increase in hemoglobin level 1 month after 200 mg of iron sucrose daily for 5 days.

REFERENCE TEST

Bone marrow iron (assessed using aspiration and Perls' stain), depleted versus replete, at baseline.

MEASUREMENTS

Area under the receiver operating characteristic curve (AUROC), sensitivity, and specificity of peripheral-iron indices and erythropoietic response to describe bone marrow iron stores.

RESULTS

Bone marrow iron stores were depleted in 48% of patients at baseline. In iron-depleted versus -replete subjects, mean hemoglobin level, median TSAT index, median serum ferritin level, and hemoglobin level increase after iron sucrose administration were 8.74 +/- 1.1 (SD) versus 9.22 +/- 0.9 g/dL (P = 0.02), 19% (interquartile range [IQR], 15%) versus 28% (IQR, 12%; P < 0.001), 100 (IQR, 131) versus 220 ng/mL (IQR, 213; P < 0.001), and 1.2 +/- 0.4 versus 0.8 +/- 0.3 g/dL (P < 0.001), respectively. TSAT, ferritin level, and increase in hemoglobin level AUROCs were similar: 0.75 (95% CI, 0.66-0.85), 0.76 (95% CI, 0.66-0.85), and 0.74 (95% CI, 0.65-0.84), respectively.

LIMITATIONS

Bone marrow iron as the index of iron stores.

CONCLUSIONS

Half the anemic patients with CKD stages 3-5 had depleted iron stores. Peripheral-iron indices and erythropoietic response had equivalent, but limited, utility in identifying depletion of bone marrow iron stores. Use of these indices to indicate depletion of iron stores should be reconsidered.

Iron and clinical outcomes in dialysis and non-dialysis-dependent chronic kidney disease patients

Abnormal iron homeostasis plays an important role in the anemia of chronic kidney disease (CKD). Although iron overload was the main complication seen in the pre-erythropoiesis-stimulating agent era, relative iron deficiency is much more common today in patients with CKD. Maintaining certain "desirable" levels of commonly used markers of iron stores (such as transferrin saturation ratio and serum ferritin) have become the goal of iron management in clinical practice, yet it is unclear whether achievement and maintenance of these "desirable" levels translates into improved clinical outcomes. This review examines issues related to iron and long-term clinical outcomes from an epidemiologic perspective, with the goal to determine what an ideal therapeutic approach should be in clinical practice and what future research is required to clarify important practical questions. Particular attention is devoted to patients with non-dialysis-dependent CKD because the management of iron homeostasis in this group of patients poses additional intriguing questions.