The relationship of initial transferrin saturation to cardiovascular parameters and outcomes in patients initiating dialysis

Absolute iron deficiency, coronary artery calcification and cardiovascular mortality in maintenance haemodialysis patients

AIM

The effects of iron on vascular calcification in rats and vascular smooth muscle cells were recently reported, but clinical studies on iron and vascular calcification are scant. We studied the associations of absolute iron deficiency, coronary artery calcification and mortality in patients with maintenance haemodialysis (MHD).

METHODS

Transferrin saturation (TSAT), ferritin, mean corpuscular haemoglobin (MCH) and Agatston coronary artery calcium score (CACS) were studied at baseline in MHD patients and followed up for 3 years. Cox proportional hazard analyses for mortality and linear regression analyses for CACS were performed.

RESULTS

In 306 patients, the median age was 67 (56-81) years, dialysis duration was 76 (38-142) months, and diabetes prevalence was 42.5%. Fifty-two patients had died by 3 years. Patients with absolute iron deficiency (TSAT <20% and ferritin <100 ng/mL) (n = 102) showed significantly higher CACS (p = .0266) and C-reactive protein (p = .0011), but a lower frequency of iron formulation administration compared with patients without absolute iron deficiency at baseline (n = 204). Absolute iron deficiency was a significant predictor for 3-year cardiovascular (CV) mortality (hazard ratio: 2.08; p = .0466), but not for 3-year all-cause mortality. CACS was significant predictor for both 3-year CV and all-cause mortality (p <.05). Absolute iron deficiency and MCH were significant determinants of CACS (p < .05).

CONCLUSION

MHD patients with absolute iron deficiency showed significantly higher CACS than others, and absolute iron deficiency was a significant risk factor for coronary artery calcification and 3-year CV mortality in MHD patients, but was not a significant predictor for 3-year all-cause mortality.

Unresolved aspects in the management of renal anemia, a Delphi consensus of the Anemia Group of the S.E.N

Anemia is a common complication of chronic kidney disease (CKD) and is associated with a decrease in quality of life and an increased risk of transfusions, morbidity and mortality, and progression of CKD. The Anemia Working Group of the Sociedad Española de Nefrología conducted a Delphi study among experts in anemia in CKD to agree on relevant unanswered questions by existing evidence. The RAND/UCLA consensus methodology was used. We defined 15 questions with a PICO structure, followed by a review in scientific literature databases. Statements to each question were developed based on that literature review. Nineteen experts evaluated them using an iterative Two-Round Delphi-like process. Sixteen statements were agreed in response to 8 questions related to iron deficiency and supplementation with Fe (impact and management of iron deficiency with or without anemia, iron deficiency markers, safety of i.v. iron) and 7 related to erythropoiesis stimulating agents (ESAs) and/or hypoxia-inducible factor stabilizers (HIF), reaching consensus on all of them (individualization of the Hb objective, impact and management of resistance to ESA, ESA in the immediate post-transplant period and HIF stabilizers: impact on ferrokinetics, interaction with inflammation and cardiovascular safety). There is a need for clinical studies addressing the effects of correction of iron deficiency independently of anemia and the impact of anemia treatment with various ESA on quality of life, progression of CKD and cardiovascular events.

Association between Iron Status and Survival in Patients on Chronic Hemodialysis

The aim of this study was to evaluate survival rates according to iron status in patients undergoing maintenance hemodialysis (HD). Thus, the National HD Quality Assessment Program dataset and claims data were used for analysis (n = 42,390). The patients were divided into four groups according to their transferrin saturation rate and serum ferritin levels: Group 1 (n = 34,539, normal iron status); Group 2 (n = 4476, absolute iron deficiency); Group 3 (n = 1719, functional iron deficiency); Group 4 (n = 1656, high iron status). Using univariate and multivariable analyses, Group 1 outperformed the three other groups in terms of patient survival. Using univariate analysis, although Group 2 showed a favorable trend in patient survival rates compared with Groups 3 and 4, the statistical significance was weak. Group 3 exhibited similar patient survival rates to Group 4. Using multivariable Cox regression analysis, Group 2 had similar patient survival rates to Group 3. Subgroup analyses according to sex, diabetic status, hemoglobin level ≥ 10 g/dL, and serum albumin levels ≥ 3.5 g/dL indicated similar trends to those of the total cohort. However, subgroup analysis based on patients with a hemoglobin level < 10 g/dL or serum albumin levels < 3.5 g/dL showed a weak statistical significant difference compared with those with hemoglobin level ≥ 10 g/dL, or serum albumin levels ≥ 3.5 g/dL. In addition, the survival difference between Group 4 and other groups was greater in old patients than in young ones. Patients with a normal iron status had the highest survival rates. Patient survival rates were similar or differed only modestly among the groups with abnormal iron status. In addition, most subgroup analyses revealed similar trends to those according to the total cohort. However, subgroup analyses based on age, hemoglobin, or serum albumin levels showed different trends.

How to diagnose iron deficiency in chronic disease: A review of current methods and potential marker for the outcome

Iron deficiency (ID) is the most common nutritional disorder worldwide. It is often observed in patients with chronic diseases, such as heart failure (HF), chronic kidney disease (CKD), inflammatory bowel disease (IBD) and cancer. ID is associated with poor clinical outcome, including poor performance, reduced quality of life, as well as increased hospitalization and mortality. The aim of this review is to provide an overview about the role of ID in chronic diseases (HF, CKD, IBD, cancer) regarding their current definitions and clinical relevance; diagnostic accuracy of iron parameters in chronic inflammatory conditions and its potential as prognostic markers. Due to different definitions and guideline recommendations of ID, various laboratory parameters for ID diagnostic exist and there is no general consensus about the definition of ID and its treatment. Still, a general trend can be observed across all investigated indications of this review (HF, CKD, IBD, cancer) that serum ferritin and transferrin saturation (TSAT) are the two parameters mentioned most often and emphasized in all guidelines to define ID and guide treatment. The most commonly used threshold values for the diagnosis of ID are TSAT of < 20% and serum ferritin of < 100-300 µg/L. Noteworthy, both TSAT and particularly ferritin are frequently applied, but both may vary due to inflammatory conditions. Studies showed that TSAT is less affected by inflammatory processes and may therefore be more accurate and reliable than serum ferritin, particularly in conditions with elevated inflammatory state. A low iron status and particularly a low TSAT value was associated with a poor outcome in all investigated indications, with the strongest evidence in HF patients. Routine surveillance of iron status in these groups of patients with chronic conditions is advisable to detect ID early. Depending on the inflammatory state, TSAT < 20% may be the more accurate diagnostic marker of ID than ferritin. Moreover, TSAT may also be the more reliable estimate for the prognosis, particularly in HF.

Associations of Air Pollution and Serum Biomarker Abnormalities in Individuals with Hemodialysis-Dependent Kidney Failure

BACKGROUND

Ambient particles with a median aerodynamic diameter of <2.5 µm (PM2.5) is a ubiquitous air pollutant with established adverse health consequences. While postulated to promote a systemic inflammatory response, limited studies have demonstrated changes in serum biomarkers related to PM2.5 exposure. We aim to examine associations between short-term PM2.5 exposure and commonly measured biomarkers known to be affected by inflammation among patients receiving maintenance in-center hemodialysis.

METHODS

We conducted a retrospective open cohort study from January 1, 2008, to December 31, 2014. Adult hemodialysis patients were identified from the United States Renal Data System and linked at the patient level to laboratory data from a large dialysis organization. Daily ambient PM2.5 was estimated on a 1-km grid and assigned to cohort patients based on the ZIP codes of dialysis clinics. Serum albumin, serum ferritin, transferrin saturation (TSAT), and serum hemoglobin were ascertained from the dialysis provider organization database. Mixed-effect models were used to assess the changes in biomarker levels associated with PM2.5 exposure.

RESULTS

The final cohort included 173,697 hemodialysis patients. Overall, the daily ZIP-level ambient PM2.5 averages were 8.4-8.5 µg/m3. A 10-µg/m3 increase in same-day ambient PM2.5 exposure was associated with higher relative risks of lower albumin (relative risk [RR], 1.01; 95% confidence interval [95% CI], 1.01 to 1.02) and lower hemoglobin (RR, 1.02; 95% CI, 1.01 to 1.03). Associations of same-day ambient PM2.5 exposure and higher ferritin and lower TSAT did not reach statistical significance.

CONCLUSIONS

Short-term PM2.5 exposure was associated with lower serum hemoglobin and albumin among patients receiving in-center hemodialysis. These findings lend support to the role of inflammation in PM2.5 exposure-outcome associations.

The Impact of Intravenous Iron Supplementation on Hematinic Parameters and Erythropoietin Requirements in Hemodialysis Patients

INTRODUCTION

Anemia is one of the most common complications of chronic kidney disease (CKD). As a result of the side effects of high doses of recombinant human erythropoietin (rhEPO) and the differences in the standard dose of the injectable iron, this study aimed to evaluate the effect of high and low intravenous iron supplementation on hematinic parameters and EPO requirements in patients under hemodialysis.

METHODS

This multicenter, randomized, double-blind clinical trial was conducted on 60 patients with CKD admitted to Sina and 29 Bahman hospitals in Tabriz, Iran in 2019-2020 to undergo hemodialysis. In the two studied groups, low (100 mg/week) and high (400 mg/week) doses of iron were administered and subjects were followed up for 6 months. The incidence of acute myocardial ischemia, stroke, and mortality during 6 months was recorded.

RESULTS

The required rhEPO dosage (mg/week) to maintain hemoglobin levels between 10 and 12 g/dL in the high-dose iron group was significantly decreased during the follow-up period (52,129.03 ± 23,810 vs. 45,760 ± 20,978.71, P ≤ 0.028). Transferrin saturation (TSAT) index had a significant upward trend after iron injection and significant correlations with the serum levels of Fe (r ≥ 0.353, P ≤ 0.007), ferritin (r ≥ 0.315, P ≤ 0.016), and total iron binding capacity (r ≥ 0.219, P < 0.050) during the follow-up period in the studied groups.

CONCLUSION

High-dose intravenous iron (400 mg/week) can reduce the mean dose of rhEPO requirements and increase the TSAT index over a period of 6 months in hemodialysis patients. High-dose IV iron administration can decrease cardiovascular events in hemodialysis patients with iron deficiency anemia.

Mean corpuscular hemoglobin concentration: an anemia parameter predicting cardiovascular disease in incident dialysis patients

BACKGROUND

Hemoglobin levels usually decline before dialysis initiation. The influence of overhydration on anemia progression and iron sequestration is poorly documented. Furthermore, clinical implications of anemia at dialysis initiation remain to be elucidated.

METHODS

This multicenter retrospective cohort study enrolled incident dialysis patients. The patients were stratified by tertiles of overhydration rate (OH-R) defined by (BW - DW)/DW*100 (BW: body weight just before dialysis initiation, DW: dry weight). Time courses (6 months before, to 1 month after, dialysis initiation) of hemoglobin, C-reactive protein (CRP), and iron sequestration index (ISI) were examined using mixed effects models. We used Cox models to identify anemia parameters predicting subsequent cardiovascular disease (CVD).

RESULTS

Among the 905 enrolled patients, hemoglobin levels gradually decreased before dialysis initiation and rapidly increased thereafter. An inverse V-shaped time course was observed for CRP and ISI with an increase during dialysis initiation. Patients with a higher OH-R showed lower hemoglobin levels along with higher CRP and ISI levels before dialysis initiation. Mean corpuscular hemoglobin concentration (MCHC) was more stable before dialysis initiation than were mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH). Low MCHC (< 32 g/dL) was independently associated with the incidence of nonatherosclerotic CVD. Patients with low MCHC tended to have increased left ventricular wall thickness and left atrial diameter.

CONCLUSIONS

Progression of anemia before dialysis among overhydrated patients may mainly occur through hemodilution and iron sequestration partly induced by inflammation. Low MCHC reflects left atrial overload and left ventricular hypertrophy and hence may predict nonatherosclerotic CVD.

Low transferrin saturation (TSAT) and high ferritin levels are significant predictors for cerebrovascular and cardiovascular disease and death in maintenance hemodialysis patients

Patients with high serum ferritin and low transferrin saturation (TSAT) levels could be considered as presenting with dysutilization of iron for erythropoiesis. However, the long-term safety of iron administration in these patients has not been well established. An observational multicenter study was performed over 3 years. In 805 patients undergoing maintenance hemodialysis (MHD), we defined dysutilization of iron for erythropoiesis in patients with lower TSAT (<20%) and higher ferritin (≥100 ng/mL) levels. A time-dependent Cox hazard model was used for the evaluation of the association between dysutilization of iron for erythropoiesis and adverse events and survival. Patients with low TSAT levels showed an increased risk of cerebrovascular and cardiovascular disease (CCVD) and death compared to patients with normal or higher TSAT levels. Patients with low ferritin and high TSAT levels had a significantly lower risk of CCVD and death compared with patients with high ferritin and low TSAT levels. Higher TSAT levels were associated with male gender, age, the absence of diabetes, low levels of high-sensitivity CRP, and low β2 microglobulin levels, but not with intravenous iron administration or ferritin levels. Although patients with low TSAT levels had a significantly higher risk of CCVD or death, high TSAT levels were not linked with iron administration. Patients, who were suspected of dysutilization of iron for erythropoiesis, had a higher risk of CCVD and death. The administration of iron should be performed cautiously for improving TSAT levels, as iron administration could sustain TSAT levels for a short term.

Freestanding Dialysis Facility Quality Incentive Program Scores and Mortality Among Incident Dialysis Patients in the United States

RATIONALE & OBJECTIVE

The Centers for Medicare & Medicaid Services introduced the Quality Incentive Program (QIP) along with the bundled payment reform to improve the quality of dialysis care in the United States. The QIP has been criticized for using easily obtained laboratory indicators without patient-centered measures and for a lack of evidence for an association between QIP indicators and patient outcomes. This study examined the association between dialysis facility QIP performance scores and survival among patients after initiation of dialysis.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

Study participants included 84,493 patients represented in the US Renal Disease System's patient-level data who had initiated dialysis between January 1, 2013, and December 1, 2013, and who did not, during the first 90 days after dialysis initiation, die, receive a transplant, or become lost to follow-up. Patients were followed up for the study outcome through March 31, 2014.

PREDICTOR

Dialysis facility QIP scores.

OUTCOME

Mortality.

ANALYTICAL APPROACH

Using a unique facility identifier, we linked Medicare freestanding dialysis facility data from 2015 with US Renal Disease System patient-level data. Kaplan-Meier product limit estimator was used to describe the survival of study participants. Cox proportional hazards regression was used to assess the multivariable association between facility performance scores and patient survival.

RESULTS

Excluding patients who died during the first 90 days of dialysis, 11.8% of patients died during an average follow-up of 5 months. Facilities with QIP scores<45 (HR, 1.39; 95% CI, 1.15-1.68) and 45 to<60 (HR, 1.21; 95% CI, 1.10-1.33) had higher patient mortality rates than facilities with scores≥90.

LIMITATIONS

Because the Centers for Medicare & Medicaid Services have revised QIP criteria each year, the findings may not relate to years other than those studied.

CONCLUSIONS

Dialysis facilities characterized by lower QIP scores were associated with higher rates of patient mortality. These findings need to be replicated to assess their consistency over time.

Long-term maintenance of hemoglobin levels in hemodialysis patients treated with bi-weekly epoetin beta pegol switched from darbepoetin alfa: a single-center, 12-month observational study in Japan

Recent evidence on maintenance administration of epoetin beta pegol, a continuous erythropoiesis receptor activator (CERA), in dialysis patients shows the clinical benefit of bi-weekly administration (Q2W) in improving hematopoiesis and iron use efficiency. We undertook a single-center observational study of 33 Japanese maintenance dialysis patients, whose anemia had been kept stable through weekly administration (Q1W) of darbepoetin (DA), to evaluate the effectiveness of CERA Q2W switched from DA in maintaining hemoglobin (Hb) levels over a 12-month period. The target Hb level was 10.0-12.0 g/dL. Throughout the 12-month period, the mean Hb was stably maintained at 10.5-10.8 g/dL, 69.7-87.9% of the patients achieving the target Hb level. The mean CERA dose was within the range of 62.9-78.8 µg/2 weeks. The average CERA dose adjustment frequency after switching was low at 0.42-0.67 times/3 months. In both subgroups stratified by the DA dose prior to the switch, Hb levels were kept stable during CERA administration; however, in the low-dose group (10-20 µg/week of DA), the CERA and iron doses decreased over time, whereas in the high-dose group (30-60 µg/week of DA) they remained unchanged. CERA Q2W achieved long-term successful anemia management in Japanese maintenance dialysis patients after switching from DA Q1W. CERA dose was adjusted based on an overall consideration of past changes in Hb levels, erythropoiesis-stimulating agent and iron doses. Subgroup analysis showed the CERA dose in the low-dose group decreased continuously, due possibly to a long-term improvement in iron use efficiency.

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.

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.

Timing of commencement of maintenance dialysis and mortality in young and older adults in Singapore

BACKGROUND

The benefit of early dialysis initiation remains controversial with a paucity of data in Asians. Therefore, we undertook this study to investigate the association between timing of initiation of dialysis and mortality in Singapore.

METHODS

The study used data from the Singapore Renal Registry database on 3286 patients with incident end-stage renal disease (ESRD) who commenced maintenance dialysis between January 2008 and December 2011. The data was further linked with the National Death Registry to acquire survival information until December 2013. We classified serum creatinine-based, estimated glomerular filtration rate (eGFR) by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation at the start of dialysis into 3 categories: Early (≥10 ml/min/1.73m2), intermediate (5 to <10 ml/min/1.73m2) and late (<5 ml/min/1.73m2).

RESULTS

In the unadjusted analysis, both early and intermediate dialysis initiation groups were at greater risk of death relative to late dialysis (Early: HR = 2.47; Intermediate: HR = 1.54). In the multivariate model, a significant interaction was detected between age and eGFR at dialysis initiation (p = 0.04). Adjusted mortality risk progressively increased with earlier initiation of dialysis for patients aged 18-54 years (p = 0.006) and aged 55 to 64 years (p < 0.001), and no statistically significant difference was observed for patients aged 65 years or older (p = 0.12).

CONCLUSIONS

Early versus later initiation of dialysis was associated with significantly higher risk of mortality in Singapore's non-elderly population, and appeared to offer no survival advantage among the elderly.

Diastolic dysfunction is an independent predictor of cardiovascular events in incident dialysis patients with preserved systolic function

Background

Diastolic heart failure (HF), the prevalence of which is gradually increasing, is associated with cardiovascular (CV) morbidity and mortality in the general population and, more specifically, in patients with end-stage renal disease (ESRD). However, the impact of diastolic dysfunction on CV outcomes has not been studied in incident dialysis patients with preserved systolic function.

Methods

This prospective observational cohort study investigates the clinical consequence of diastolic dysfunction and the predictive power of diastolic echocardiographic parameters for CV events in 194 incident ESRD patients with normal or near normal systolic function, who started dialysis between July 2008 and August 2012.

Results

During a mean follow-up duration of 27.2 months, 57 patients (29.4%) experienced CV events. Compared to the CV event-free group, patients with CV events had a significantly higher left ventricular (LV) mass index, ratio of early mitral flow velocity (E) to early mitral annulus velocity (E’) (E/E’), LA volume index (LAVI), deceleration time, and right ventricular systolic pressure, and a significantly lower LV ejection fraction and E’. In multivariate Cox proportional hazard analysis, E/E’>15 and LAVI>32 mL/m² significantly predicted CV events (E/E’>15: hazard ratio [HR] = 5.40, 95% confidence interval [CI] = 2.73–10.70, P< .001; LAVI>32 mL/m²: HR = 5.56, 95% CI = 2.28–13.59, P< .001]. Kaplan-Meier analysis revealed that patients with both E/E’>15 and LAVI>32mL/m² had the worst CV outcomes.

Conclusion

An increase in E/E’ or LAVI is a significant risk factor for CV events in incident dialysis patients with preserved LV systolic function.

Low levels of serum ferritin lead to adequate hemoglobin levels and good survival in hemodialysis patients

BACKGROUND

The optimal level of serum ferritin (s-ft) for anemia control and good survival in hemodialysis (HD) patients remains unclear. A 10-year survey was performed to clarify the appropriate quantities of s-ft and investigate the relationships among s-ft, transferrin saturation (TSAT), and mortality in HD patients.

METHODS

HD outpatients (n = 125) treated with erythropoiesis-stimulating agents (ESA) were followed for 10 years. The ESA and low-dose iron supplement dosages were adjusted to maintain the hemoglobin (Hb) at 10-11 g/dl, according to Japanese guidelines. The Kaplan-Meier method, log-rank tests, and the Cox proportional hazards model were used for performing the statistical analyses. The interactions among the Hb, s-ft, and TSAT were analyzed using a multiple linear regression model. Patients with TSAT ≥20% were classified according to the s-ft cutoff values: group 1 (s-ft <30 ng/ml); group 2 (s-ft 30-80 ng/ml); group 3 (s-ft >80 ng/ml); TSAT <20% was a predictor of poor outcome.

RESULTS

The survival rate in group 2 was significantly higher than that in other groups (p = 0.013), and the Cox proportional hazards model analysis showed a good effect of low levels of s-ft on patients' survival. The multiple linear regression model showed a strong effect of s-ft on the Hb (log [s-ft], β-coefficient -0.45: 95% confidence interval -0.65 to -0.26, p < 0.001).

CONCLUSION

This study revealed that low levels of s-ft have a beneficial effect on the outcome of HD patients receiving ESA. Thus, the optimal s-ft level might be lower than that established previously for these patients.

Intravenous iron exposure and mortality in patients on hemodialysis

BACKGROUND AND OBJECTIVES

Clinical trials assessing effects of larger cumulative iron exposure with outcomes are lacking, and observational studies have been limited by assessment of short-term exposure only and/or failure to assess cause-specific mortality. The associations between short- and long-term iron exposure on all-cause and cause-specific mortality were examined.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The study included 14,078 United States patients on dialysis initiating dialysis between 2003 and 2008. Intravenous iron dose accumulations over 1-, 3-, and 6-month rolling windows were related to all-cause, cardiovascular, and infection-related mortality in Cox proportional hazards models that used marginal structural modeling to control for time-dependent confounding.

RESULTS

Patients in the 1-month model cohort (n=14,078) were followed a median of 19 months, during which there were 27.6% all-cause deaths, 13.5% cardiovascular deaths, and 3% infection-related deaths. A reduced risk of all-cause mortality with receipt of >150-350 (hazard ratio, 0.78; 95% confidence interval, 0.64 to 0.95) or >350 mg (hazard ratio, 0.79; 95% confidence interval, 0.62 to 0.99) intravenous iron compared with >0-150 mg over 1 month was observed. There was no relation of 1-month intravenous iron dose with cardiovascular or infection-related mortality and no relation of 3- or 6-month cumulative intravenous iron dose with all-cause or cardiovascular mortality. There was a nonstatistically significant increase in infection-related mortality with receipt of >1050 mg intravenous iron in 3 months (hazard ratio, 1.69; 95% confidence interval, 0.87 to 3.28) and >2100 mg in 6 months (hazard ratio, 1.59; 95% confidence interval, 0.73 to 3.46).

CONCLUSIONS

Among patients on incident dialysis, receipt of ≤ 1050 mg intravenous iron in 3 months or 2100 mg in 6 months was not associated with all-cause, cardiovascular, or infection-related mortality. However, nonstatistically significant findings suggested the possibility of infection-related mortality with receipt of >1050 mg in 3 months or >2100 mg in 6 months. Randomized clinical trials are needed to assess the safety of exposure to greater cumulative intravenous iron doses.