Erythropoietin Friend or Foe in Chronic Kidney Disease Anemia: An Analysis of Randomized Controlled Trials, Observational Studies and Meta-analyses.

Amir Hayat

Introduction:

According to The National Kidney Foundation of The United States of America ¹ CKD is defined as (1) evidence of kidney damage based on abnormal urinalysis results (e.g., proteinuria, hematuria) or structural abnormalities observed on ultrasound images or (2) an absolute GFR of less than 60 mL/min for 3 or more months. Based on this definition there are five stages. See Table 1. Anemia affects 60% to 80% of patients with chronic kidney disease (CKD) and reduces their quality of life. Treatment options are blood transfusion, epoietin alfa and darbepoetin alfa ^2 . Anemia of CKD is, in most patients, normocytic and normochromic and primarily caused by depressed production of erythropoietin (EPO), oxidative stress and inflammation, erythropoiesis inhibition and reduction in red blood cell survival ^3,4,5 . The other cause of anemia is deficiency of iron. The dialysis patient is in a state of continuous iron loss from gastrointestinal bleeding, blood drawing, and/or, most important with hemodialysis (HD), the dialysis treatment itself. HD patients lose an average of 2 g of iron per year. Thus, iron deficiency will develop in virtually all dialysis patients receiving EPO unless supplemental iron therapy is given orally or intravenously. DRIVE study, a randomized trial study, adds direct evidence that administration of intravenous iron to patients with functional iron deficiency who were on supplemental EPO therapy results in increase in the hemoglobin level ⁶. The aim of this review is to assess that whether Erythropoietin (EPO) treatment is beneficial or harmful in the management of anemia associated with CKD. To address these issues, we have analyzed randomized controlled trials, observational studies and meta-analyses.
 
Table 1: Stages of CKD according to NKF.

 
Methods:

Search strategy: The search strategy was designed to capture the patient population, suffering from CKD on supplemental erythropoietin (EPO) therapy. Literature search (1989 to 2008) was carried out using MEDLINE, PubMed as well as other electronic databases and in online journals using the keywords "Kidney failure, chronic and "erythropoietin" for studies up to 1996, and "epoetin alfa" for subsequent years.
 
Selection of studies: All papers identified were English-language, full text papers. In addition, the reference lists of identified relevant articles were also searched. The search was not limited to any specific study design, and we searched for randomized controlled trials (RCTs), observational studies, systemic review and meta-analysis. Citations identified in the literature search were independently screened by author to select potentially relevant articles. The full articles from this list were retrieved and subsequently reviewed by author for inclusion in the systematic review. During selection preference was given to articles published within last five years. Articles were included if they met the following inclusion criteria 1) published in a peer reviewed journal; 2) written in English; 3) reported randomized controlled trials of EPO; 4) observational studies regarding EPO and quality of life; 5) Review articles and meta-analyses about EPO therapy in CKD patients.
 
Results:
470 citations were identified in search from PubMed, Medline and from other online journals. Of these 470 citations, 444 did not meet the selection criteria and were excluded, leaving 26. Out of 26 citations 11 were RCTs, 10 were observational studies and 5 were reviews and meta-analysis.
 
Five studies (Parfrey et al⁷, Foley et al⁸, Furuland et al⁹, Drüeke et al¹⁰, and Canadian Erythropoietin Study Group¹¹) showed that correction of anemia result in improvement of quality of life, although the singh et al¹² showed such improvement with partial correction of anemia, and no detectable difference in the quality of life was evident in Roger et al¹³ study. Five studies Parfrey et al⁷, Foley et al⁸ and Levin et al¹⁴ and McMahon et al¹⁵ and Roger et al¹³ showed that normalization of hemoglobin does not lead to regression of established concentric LV hypertrophy or LV dilation. It may, however, prevent the development of LV dilation. In McMahon et al¹⁵ study the only factor that seemed to predict normalization of LV mass in patients who had LV hypertrophy at study entry was a lower pulse pressure. One study Sikole et al¹⁶ correction of renal anemia can normalize heart morphology and improve heart function. Three studies Besarab et al¹⁷, Drüeke et al¹⁰ and Singh et al¹² demonstrated increased cardiovascular events whereas two studies Drüeke et al¹⁰ and Singh et al¹² also showed progression to dialysis in patients assigned to the highest hemoglobin targets (>13.0 g/dL), compared with <12 g/dL, trial design of three studies was same in respect that both arms were on EPO. In comparison to Drüeke et al¹⁰ and Singh et al¹² studies, in Roger et al¹³ study the renal function was not adversely affected in the group randomized to the higher Hb. (Table 2).
 
Table 2: Randomized controlled trials (RCTs)

 
Both Phrommintikul et al¹⁸andGiovanni et al¹⁹ addressed the similar issues, to evaluate the benefits and harms of different hemoglobin (Hb) targets in CKD in their meta-analyses. They reached to similar conclusion, increase in the risk of all-cause mortality in anemic patients with CKD in whom a higher Hb target (in the normal physiological range) is aimed for with treatment with EPO. Such patients are also at an increased risk of arteriovenous access thrombosis and poorly controlled hypertension, which could contribute to the increased risk of mortality. Furthermore, there seems to be no beneficial effect on left ventricular mass in such patients. There were similarities and differences in inclusion criteria. Both used the trials targeting different Hb concentrations in patients with anemia caused by CKD, majority of trials analyzed were different except 4 trials which were same in both. The difference in inclusion criteria was that Giovanni et. al analyzed two groups of studies: The first group contained studies in which the intervention was to achieve different Hb targets compared (higher versus lower Hb targets), both arms were on EPO and trials included individuals with clinical cardiovascular disease. The second group compared EPO treatment with no EPO treatment. The results of these two groups of studies were analyzed separately. In Phrommintikul only one group of studies “EPO treatment with no EPO treatment” was analyzed. Meta-analysis by Phrommintikul et alincludes nine RCTs, which enrolled 5143 patients.
 
In Jones et al²⁰ meta-analysis both randomized controlled trials and uncontrolled trial were analyzed, all studies were of the “pre/post” design, in that measurements of anemia, quality of life, hospitalizations, and transfusions were taken before and after initiation of EPO therapy. They drew these conclusions from 16 published studies of which 5 were randomized clinical trials. He found that treatment with EPO raised hemoglobin levels, reduced transfusion requirements and improved quality of life. For quality of life outcome in these meta-analysis please review Table 3.
 
Table: 3 Meta-analysis.

Discussion:
Erythropoietin (EPO) has become an essential part of the management of anemic patients with CKD. It is also used to treat the anemia associated with chemotherapy and other diseases, and it improves quality of life ^21,22 . The introduction of EPO in 1989 significantly improved the clinical management of anemia of CKD. By 2005, 99% of incenter hemodialysis patients received EPO treatment for their anemia. EPO dosing has changed dramatically in the past decade and a half; between 1991 and 2005, the mean dose of EPO increased about 4-fold in dialysis patients. Today, EPO therapy is the largest single Medicare drug expenditure totaling $1.8 billion in 2004 (an increase of 17% from 2003) and EPO comprised 11% of all Medicare ESRD costs ²³
 
EPO and left ventricular hypertrophy. Randomized vs. Observational studies. Anemia is a contributing factor in many of the symptoms associated with reduced kidney function. These include fatigue, depression, reduced exercise tolerance, dyspnea. Data from observational studies shows that severe anemia may results in cardiovascular consequences, such as left ventricular hypertrophy (LVH) and left ventricular systolic dysfunction ²⁴. Left ventricular hypertrophy (LVH) is present in nearly 80% of dialysis patients and is associated with higher rates of cardiovascular events ^25. It is also associated with an increased risk of morbidity and mortality principally due to cardiac disease and stroke ^26,27. As a result, patients with anemia due to CKD are at increased risk of hospitalization, hospital length of stay, reduced quality of life and mortality ^28. Uncontrolled studies suggested that partial correction of anemia with EPO therapy may result in prevention or regression of CHF ²⁹ and LVH ^30,31. Several randomized controlled trials showed that left ventricular hypertrophy was not further improved by a complete correction of anemia compared to only partial correction ^{7,13,14,15,17.} Robert N Foley et al. randomly assigned 146 patients with either concentric LV hypertrophy or LV dilation to receive EPO to achieve hemoglobin levels of 10 or 13.5 g/dL. He concluded that normalization of hemoglobin does not lead to regression of established concentric LV hypertrophy or LV dilation. It may, however, prevent the development of LV dilation, and it leads to improved quality of life ^8. Partial correction of severe anemia <8 or 9g/dl to mild anemia (10-11 g/dL) likely reduces mortality, but further treatment to higher Hb levels has not been shown to further reduce mortality, and has actually increased mortality. Controlled studies with quality of life (QOL) and left ventricular mass as end points support partial correction of hemoglobin in dialysis patients ^11,13,16,32,  The fact that anemic renal failure patients have more LVH than non-anemic renal failure patients does not prove that anemia causes LVH. Vaziri et al in a review mentioned that the real culprits are oxidative stress, inflammation and diminished biological capacity that simultaneously cause treatment-resistant anemia and adverse cardiovascular and other outcomes ^33.
 
EPO and quality of life:Numerous randomized, controlled trials have demonstrated that EPO significantly raises hemoglobin levels, reduces transfusion requirements, and improves quality of life in anemic patients with chronic renal failure. Lefebvre et al conducted an analysis on data from a multicenter, open-label, prospective study of EPO for anemia in patients with CKD not on dialysis to evaluate the relationship between Hb level and quality of life (QOL). The results showed that the maximal incremental gain in QOL occurred when Hb reached 11 to 12 g/dL. This suggests that treating anemic patients with non-dialysis CKD until their Hb level reaches 12 g/dL will result in the greatest QOL improvement per Hb unit increase ^34.
 
Randomized vs. Observational studies. Many randomized controlled trials suggest an association between higher hemoglobin level and improved quality of life, physical function, and exercise capacity ^7,8,9,35 but the association with survival is less clear. Whereas observational studies have generally shown increased survival with higher hemoglobin level ^{36,37,38,39,40} randomized trials have not shown such benefits. The extent anemia of inflammation varies between patients with renal failure. It is this factor that likely explains the following paradox: in observational studies, higher hemoglobin associates with better survival in CKD, while in controlled trials, higher hemoglobin achieved by escalated EPO dosing decreases survival. In the observational studies, those with the higher Hb levels were likely those patients who had the least component of anemia of inflammation, and therefore less resistant to EPO supplementation; they survived better not because they had better hemoglobin, but because they had less burden of inflammatory disease. Anemia of chronic disease is a highly conserved response that is mediated by multiple mechanisms acting in concert to lower the hemoglobin in the face of inflammation, and should be presumed until proven otherwise to be adaptive for most patients who exhibit it. That this is so is supported by the observation that the correction of anemia confers lower survival not only in renal failure, but also in cancer patients and in patients in the critical care unit.
 
Jones et al. in their very thorough meta-analysis ²⁰ indeed found that treatment with EPO raised hemoglobin levels, reduced transfusion requirements and improved quality of life. Studies have demonstrated that morbidity and mortality rates are lower when hematocrit values are within the Disease Outcomes Quality Initiative (DOQI) target range (33 to 36%) ⁴⁰. Ernesto Paoletti et alin their review of observational and randomized studies concluded from the results of observational studies that normalization of Hb in renal patients seems to be associated with further improvement in quality of life and physical activity but with no significant differences in mortality rate, hospitalization rate, and the extent of LVH regression, but the results of randomized trials show that achieving near-normal Hb did not reduce the risk for death from all causes or the risk for cardiac death. The latter risk actually increased slightly, in the group of dialysis patients with normalized Hb concentration ⁴¹. For CKD stage 3 and 4 patients, no improvement seen in CHOIR, but improvements reported in CREATE. There may be reporting bias in CREATE as it was an open label study, and the low target arm had to develop worsening anemia prior to initiating EPO therapy ^10,12
 
EPO and Cardiovascular Events:Anemia is a common complication of chronic kidney disease. Determination of the appropriate target hematocrit level for patients undergoing hemodialysis continues to be a controversial area ⁴⁰. The National Kidney Foundation Dialysis Outcomes Quality Initiative (K/DOQI) states when a decision to use EPO is made, some Hgb value in the range of 11 to 12, but no higher than 13 should generally be chosen. ⁴². The European Best Practice Guidelines (EBPGs) recommend that most patients with CKD achieve a target hemoglobin (Hb) 11 g/dl to reduce the risk of adverse outcomes ^43. Randomized vs. Observational studies. Observational studies have shown a strong  association between severity of anemia and risk of morbidity and mortality from cardiovascular disease and other causes in CKD patients ^{36,37,38,39,40}. These findings have been interpreted as evidence for the causal role of anemia in the pathogenesis of adverse outcomes in these patients. On the hand, randomized clinical trials of anemia management revealed either no effect or increased morbidity and mortality in patients assigned to normal hemoglobin Hb targets ^10,12,17. Meta- analyses of randomized clinical trials have shown a significant increase in cardiovascular and all-cause mortality and arteriovenous access thrombosis among patients assigned to the higher than those randomized to the lower Hb targets ^18,19. Meta-analysis of Phrommintikul shows a significantly higher risk of all-cause mortality (targeting a Hb level higher than 12 g/dL results in a 17% increased risk of death compared with target hemoglobin levels less than 12 g/dL), arteriovenous access thrombosis and higher risk of poorly controlled blood pressure in the higher Hb target group than in the lower target Hb. The incidence of myocardial infarction was much the same in the two groups ¹⁸. Meta-analysis of Giovanni F.M et al shows that on the basis of available randomized, controlled trials, Hb targets of <12.0 g/dL are associated with a lower risk of death in the population with cardiovascular disease and CKD compared with Hb targets of >13.0 g/dL. For every 30 patients treated to an Hb target of <12.0 g/dL compared with an Hb target of >13.0 g/dL, approximately one death is avoided ¹⁹. Two large randomized controlled trials; CREATE ^[38] and CHOIR ^[39] demonstrated increased cardiovascular events and progression to dialysis in patients assigned to the highest hemoglobin targets (>13.0 g/dL), compared with <12 g/dL. US Food and Drug Administration (FDA) warned that use of erythropoiesis-stimulating agents (ESAs) increases mortality and morbidity risk. The warning follows publication of studies suggesting that correction of anemia in patients with CKD did not reduce the risk of cardiovascular events and that reaching a target Hb level of >13 g/dL, compared with a target level of 11.3 g/dL, was associated with increased risk of cardiovascular events. FDA said recent studies had found increased risk of death, blood clots, strokes, and myocardial infarctions in patients with chronic renal disease who received ESAs at higher-than-recommended doses that maintained their hemoglobin levels at more than 12 g/dL ^44.
 
EPO and kidney:EPO has been found to interact with its receptor in a large variety of non-haematopoietic tissues, which result into cytoprotective cellular responses, like mitogenesis, angiogenesis, inhibition of apoptosis and promotion of vascular repair through mobilization of endothelial progenitor cells from the bone marrow. In experimental ischaemic and toxic acute renal failure administration of EPO, promotes renoprotection. Preliminary experimental and clinical evidence also indicates that EPO may be renoprotective in chronic kidney disease²² .EPO is used widely to treat anemia in patients with CKD, but the benefits of EPO use in patients with acute renal failure (ARF) are unclear. In vitro and animal studies suggest that EPO may promote renal recovery and decrease mortality in ARF ^45. Partial amelioration of anemia with low doses of EPO was reported to slow the rate of progression to ESRD in a group of CKD patients ^46. These cellular protection from EPO observed in animal models has not been confirmed in humans, and has been specifically addressed and disproven in large randomized trial. The CREATE study found as a secondary endpoint that early treatment with EPO increased the likelihood of starting dialysis. CHOIR found no reduction in the rate of progression of CKD in patients given more EPO (the higher target arm) compared to the lower target arm ^10,12.
 
EPO for other Indications:In recent years, studies in animals and humans have focused on the use of EPO for other indications. It has been found to play a role in both cardioprotection and neuroprotection. It has effects on the immune system, and can cause regression in hematologic diseases such as multiple myeloma. It may also improve the response of solid tumors to chemotherapy and radiation therapy ^21. Again the cellular protection from EPO observed in animal models has not been confirmed in humans.
 
EPO and Seizures:Seizures are reported to be a complication of EPO in the product information. However, in a meta-analysis conducted by Giovanni et alshowed that treating with EPO may be protective against seizures Lower Hb targets of <95 g/L in individuals who are not treated with EPO are associated with a significantly increased risk of seizures compared with treatment with EPO and Hb values of >100 g/L ¹⁹.
 
EPO and Hypertension:Administration of ESA may be associated with exacerbation of
hypertension in about 5% of patients. Robert N. Foley et alin his analysis of observational and randomized studies found that most of the trials that have been reported to date have shown that higher hemoglobin targets lead to higher BP levels and/or greater requirements for antihypertensive therapy, he drew this conclusion from nine randomized trials ^47. The mechanism of ESA induced hypertension is thought to be related to stimulation of the vascular endothelium by ESA resulting in increased circulating levels of endothelin. Furthermore the increase in hemoglobin associated with ESA therapy may increase blood viscosity resulting in vasospasm. As such routine monitoring of blood pressure is essential in patients treated with ESA ⁴⁸. Meta-analysis of Phrommintikul et al showed a significantly higher risk of poorly controlled blood pressure in the higher haemoglobin target group than in the lower target hemoglobin ¹⁸ . Giovanni et almeta-analysis showed lower Hb levels of <95 g/L with no EPO treatment are associated with a reduced risk of patients who present with hypertensive episodes. In absolute terms, the risk of developing hypertensive episodes is 16% lower with Hb values <95 g/L compared with Hb >100 g/L. For every seven patients treated to obtain an Hb >100 g/L, one patient will require additional antihypertensive medication ¹⁹
 
EPO and Access:Normalizing hemoglobin has been associated with a higher incidence of vascular access clotting ^40. Randomized, prospective, open-label trial study of Besarab et al, showed a significantly higher risk of access thrombosis with the higher Hb targe¹⁷. Meta-analysis of Phrommintikul et alshowed a significantly higher arteriovenous access thrombosis in the higher Hb target group than in the lower target Hb ^18.
 
EPO and Pure Red Cell Aplasia (PRCA):Although rare, administration of ESA may result in formation of anti-erythropoietin antibodies, thereby leading to pure red cell aplasia and erythropoietin resistance ⁴⁹ In patients in whom ESA doses have been maximized without effect and no other causes can be identified, serum anti-erythropoietin levels and bone marrow biopsy should be performed. If confirmed, erythropoietin administration should be ceased and the patient treated with periodic blood transfusions.
 
Conclusion: Achieving hemoglobin control over time is a major challenge because of the various physiological factors that influence the response in individual patients and the potential risk for increased mortality, particularly for patients with co morbidities ⁵⁰. The association data led to several hypotheses about what anemia was causing e.g. LVH, fatigue, and increased mortality. These hypotheses have been tested in RCT's and in most cases anemia is associated with but does not cause the outcome, such as LVH or mortality. Fatigue is improved somewhat by anemia treatment with EPO, and transfusion frequency is reduced, though the cost is high. In the case of EPO balance is critical. Too little treatment and patients with chronic kidney disease are subjected to a lifetime of exhaustion and blood transfusions. Too much and they could be threatened with an increased risk of death. The overall quality of life is improved when anemia is treated with EPO, but aiming for a target value of 13.5 g of hemoglobin per deciliter provided no additional quality-of-life benefit ¹².
 

Key Points:

1. Anemia is associated with bad outcomes; Anemia is nearly universal in advanced renal disease. In these patients, anemia is associated with increased cardiovascular morbidity and mortality, reduced quality of life, and accelerated renal disease progression, though those associations do not necessarily establish causation.
2. Treatment of anemia reduces transfusion requirements and improves quality of life in anemic patients with CKD.
3. Mortality increases with treatment to higher targets; Recent studies have found an increased risk of death, blood clots, strokes, and myocardial infarctions in patients with chronic renal disease who received ESAs at doses that maintained their hemoglobin levels at more than 12g/dL, leading the Food and Drug Administration to apply a 'black box' warning to the product monographs of licensed ESAs.
4. Recent studies support partial correction, not normalization of hemoglobin.
5. Current guidelines recommend target of 10-12g/dL. 

References

1- Levey AS, Coresh J, Balk E, et al: National Kidney Foundation Disease Outcomes Quality Initiative Clinic Practice Guidelines for Chronic Kidney Disease: Evaluation, Classification and Stratification. Ann Intern Med 2003 139: 137–147
2- Strippoli GF, Navaneethan SD, Craig JC, et al. Haemoglobin and haematocrit targets for the anaemia of chronic kidney disease. Cochrane Database Syst Rev. 2006 Oct 18;(4):CD003967
3-Besarab A et al. Anemia of renal disease in diseases of kidney and urinary tract. In: Schrier RW (ed). Diseases of the Kidney and Urinary Tract, 7th edn. Philadelphia, PA: Lippincott, Williams and Company, 2001, 2719–2734
4- Locatelli F, Andrulli S, Memoli B et al. Nutritional-inflammation status and resistance to erythropoietin therapy in haemodialysis patients. Nephrol Dial Transplant 2006; 2: 991–998
5- Righetti M, Ferrario GM, Milani S, et al. A single centre study about the effects of HFR on anemia. G Ital Nefrol. 2004 Nov-Dec;21 Suppl 30:S168-71.
6- Coyne DW, Kapoian T, Suki W, et al; Ferric gluconate is highly efficacious in anemic hemodialysis patients with high serum ferritin and low transferrin saturation: results of the Dialysis Patients' Response to IV Iron with Elevated Ferritin (DRIVE) Study. J Am Soc Nephrol. 2007 Mar;18(3):975-84. Epub 2007 Jan 31.
7- Parfrey PS, Foley RN, Wittreich BH, et al: Double-blind comparison of full and partial anemia correction in incident hemodialysis patients without symptomatic heart disease. J Am Soc Nephrol 16 : 2180 –2189, 2005[Abstract/Free Full Text]
8- Foley RN, Parfrey PS, Morgan J, et al. Effect of hemoglobin levels in hemodialysis patients with asymptomatic cardiomyopathy. Kidney Int 2000;58:1325-1335
9-Furuland H, Linde T, Ahlmen J, et al: A randomized controlled trial of haemoglobin normalization with epoetin alfa in pre-dialysis and dialysis patients. Nephrol Dial Transplant 18 : 353 –361, 2003[Abstract/Free Full Text]
10- Drüeke TB et al. - Normalization of Hemoglobin Level in Patients with Chronic Kidney Disease and Anemia, N Eng J Med. 2006;355:2071-2084.
11-Canadian Erythropoietin Study Group: Association between recombinant human erythropoietin and quality of life and exercise capacity of patients receiving haemodialysis. BMJ 300 : 573 –578, 1990
12- Singh AK et al. Correction of Anemia with Epoetin Alfa in Chronic Kidney Disease, N Eng J Med. 2006;355:2085-2098.
13- Roger SD, McMahon LP, Clarkson A et al. Effects of early and late intervention with epoetin alfa on left ventricular mass among patients with chronic kidney disease (stage 3 or 4): results of a randomized clinical trial. J Am Soc Nephrol 2004; 15:148-156
14- Levin A, Djurdjev O, Thompson C, et al. Canadian randomized trial of hemoglobin maintenance to prevent or delay left ventricular mass growth in patients with CKD. Am J Kidney Dis 2005;46:799-811.
15-McMahon LP, Roger SD, Levin A et al, Slimheart Investigators Group. Development, prevention, and potential reversal of left ventricular hypertrophy in chronic kidney disease. J Am Soc Nephrol 2004;15:1640-1647
16-Sikole A, Polenakovic M, Spirovska V, et al: Analysis of heart morphology and function following erythropoietin treatment of anemic dialysis patients. Artif Organs 17 : 977 –984, 1993[Medline]
17- Besarab A, Bolton WK, Browne JK, et al: The effects of normal as compared with low hematocrit values in patients with cardiac disease who are receiving hemodialysis and epoetin. N Engl J Med 339: 584–590, 1998
18- Phrommintikul A, Haas SJ, Elsik M, Krum, et al. Mortality and target hemoglobin concentrations in anaemic patients with chronic kidney disease treated with erythropoietin: a meta-analysis. Lancet 2007; 369: 381-8).
19- Giovanni F.M. Strippoli , Jonathan C. Craig , et al. Hemoglobin Targets for the Anemia of Chronic Kidney Disease: A Meta-analysis of Randomized, Controlled Trials. J Am Soc Nephrol 15: 3154-3165, 2004.
20-Jones M, Ibels L, Schenkel B, et al. Impact of epoetin alfa on clinical end points in patients with chronic renal failure: a meta-analysis. Kidney Int 2004;65:757-767
21-. Oster HS, Hoffman M, Prutchi-Sagiv S, et al. Erythropoietin in clinical practice: current use, effect on survival, and future directions. Isr Med Assoc J. 2006 Oct;8(10): 703-6
22-Johnson DW, Forman C, Vesey DA, et al. Novel renoprotective actions of erythropoietin: new uses for an old hormone. Nephrology (Carlton). 2006 Aug;11(4):306-12
23- Mae Thamer, Yi Zhang, James Kaufman, et al. Dialysis Facility Ownership and Epoetin Dosing in Patients Receiving Hemodialysis. JAMA. 2007;297:1667-1674.
24- Levin, A, Thompson, CR, Ethier, J, et al. Left ventricular mass index increase in early renal disease: impact of decline in hemoglobin. Am J Kidney Dis 1999; 34:125.
25- Foley RN, Parfrey PS, Harnett JD, et al: Clinical and echocardiographic disease in patients starting end-stage renal disease therapy. Kidney Int 47 : 186 –192, 1995[Medline]
26- McClellan, WM, Flanders, WD, Langston, RD, et al. Anemia and renal insufficiency are independent risk factors for death among patients with congestive heart failure admitted to community hospitals: a population-based study. J Am Soc Nephrol 2002; 13:1928.
27- Abramson JL, et al. Renal insufficiency, anemia, and risk of incident stroke in a middle-aged, community-based population: The ARIC study. Kidney International 2003; 64: 610-615.
28- Ma, JZ, Ebben, J, Xia, H, Collins, AJ, et al. Hematocrit level and associated mortality in hemodialysis patients. J Am Soc Nephrol 1999; 10:610.
29- Silverberg DS, Wexler D, Blum M et al. The effect of correction of anaemia in diabetics and non-diabetics with severe resistant congestive heart failure and chronic renal failure by subcutaneous erythropoietin and intravenous iron. Nephrol Dial Transplant 2003; 18: 141–146
30. Portoles J, Torralbo A, Martin P et al. Cardiovascular effects of recombinant human erythropoietin in predialysis patients. Am J Kidney Dis 1997; 29: 541–548
31. Hayashi T, Suzuki A, Shoji T et al. Cardiovascular effect of normalizing the hematocrit level during erythropoietin therapy in predialysis patients with chronic renal failure.AmJKidneyDis 2000; 35: 250–256
32-McMahon LP, Johns JA, McKenzie A, et al: Haemodynamic changes and physical performance at comparative levels of haemoglobin after long-term treatment with recombinant erythropoietin. Nephrol Dial Transplant 7 : 1199 –1206, 1992[Abstract/Free Full Text]
33- Nosratola D. Vaziri1 and Xin J. Zhou, et al. “Potential mechanisms of adverse outcomes in trials of anemia correction with erythropoietin in chronic kidney disease”. Nephrol Dial Transplant 5 Nov 2008 1 of 7
34- Lefebvre P, Vekeman F, Sarokhan B, et al. Relationship between hemoglobin level and quality of life in anemic patients with chronic kidney disease receiving epoetin alfa. Curr Med Res Opin. 2006 Oct;22(10):1929-37.]
35-Painter P, Moore G, Carlson L, et al: Effects of exercise training plus normalization of hematocrit on exercise capacity and health-related quality of life. Am J Kidney Dis 39 : 257 –265, 2002[Medline]
36-- Li S, Collins AJ, et al: Association of hematocrit value with cardiovascular morbidity and mortality in incident hemodialysis patients. Kidney Int 65 : 626 –633, 2004[CrossRef][Medline]
37-Ofsthun N, Labrecque J, Lacson E, et al: The effects of higher hemoglobin levels on mortality and hospitalization in hemodialysis patients. Kidney Int 63 : 1908 –1914, 2003[CrossRef][Medline]
38-Regidor DL, Kopple JD, Kovesdy CP, et al: Associations between changes in hemoglobin and administered erythropoiesis-stimulating agent and survival in hemodialysis patients. J Am Soc Nephrol 17 : 1181 –1191, 2006[Abstract/Free Full Text]
39-Robinson BM, Joffe MM, Berns JS, et al: Anemia and mortality in hemodialysis patients: accounting for morbidity and treatment variables updated over time. Kidney Int 68 : 2323 –2330, 2005[CrossRef][Medline]
40- Collins AJ, Li S, St Peter W, et al. Death, hospitalization, and economic associations among incident hemodialysis patients with hematocrit values of 36 to 39%. J Am Soc Nephrol 2001;12:2465-2473.
41- E. Paoletti, G. Cannella, et al. Update on Erythropoietin Treatment: Should Hemoglobin Be Normalized in Patients with Chronic Kidney Disease? J. Am. Soc. Nephrol., April 1, 2006; 17(4_suppl_2): S74 - S77.
42- KDOQI Clinical Practice Guideline and Clinical Practice Recommendations for Anemia in Chronic Kidney Disease, 2007 Update of Hemoglobin Target. American Journal of Kidney Diseases, September 2007 supplement.
43- Macdougall IC, Cooper AC, et al. Hyporesponsiveness to erythropoietic therapy due to chronic inflammation. Eur J Clin Invest (2005) 35(Suppl 3):32–35.
44- Mike Mitka et al, FDA Sounds Alert on Anemia Drugs. JAMA. 2007;297:1868-1869.
45- Park J, Gage BF, Vijayan A, et al. - Use of EPO in critically ill patients with acute renal failure requiring renal replacement therapy. Am J Kidney Dis. 2005 Nov;46(5):791-8
46- Gouva C, Nikolopoulos P, Ioannidis JP et al. Treating anemia early in renal failure patients slows the decline of renal function: a randomized controlled trial. Kidney Int 2004; 66: 753–760.
47- Robert N. Foley et al. Do We Know the Correct Hemoglobin Target for Anemic Patients with Chronic Kidney Disease?
Clin. J. Am. Soc. Nephrol, July 1, 2006; 1(4): 678 - 684.
48- Public Health Advisory : Epoetin alfa (marketed as Procrit, Epogen), Darbepoetin alfa (marketed as Aranesp) [http://www.fda.gov/cder/drug/advisory/RHE.htm]
49- Pollock C, Johnson DW, Hörl WH, et al. Pure red cell aplasia induced by erythropoiesis-stimulating agents. Clin J Am Soc Nephrol, 2008, 3(1):193-9.
50- P. Barany, H.-J. Muller, et al. Maintaining control over haemoglobin levels: optimizing the management of anaemia in chronic kidney disease. Nephrol. Dial. Transplant., June 1, 2007; 22(suppl_4): iv10 - iv18.

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