Implications of Neocytolysis for Optimal Management of Anaemia in Chronic Kidney Disease

Efficacy of daprodustat on anemia in hemodialysis patients with sustained inflammation: a case report

Hypoxia-inducible factor prolyl hydroxylase inhibitors improve anemia in CKD and dialysis patients and were approved for anemia treatment with these populations in Japan. An 89 year-old man with anemia and on maintenance hemodialysis was successfully treated with a dose-up of darbepoetin alfa from 10 to 20 μg per week, and the dose was gradually tapered to 5 μg. Later, serum hemoglobin levels decreased with the newly occurring sustained inflammation and left pleural effusion of an unknown cause, and the darbepoetin alfa dose was increased again to 20 μg per week, which was not effective. Darbepoetin alfa was switched to 4 mg of daprodustat daily, which was fairly effective under sustained inflammation, with serum hemoglobin levels maintained at 11-12 g/dL. The increase in hemoglobin levels was ascribed to the increase in the number of red blood cells, not the mean corpuscular hemoglobin level. During the inflammatory state, despite the contrasting effect on anemia by the 20 μg of darbepoetin alfa weekly and 4 mg of daprodustat daily, the reticulocyte counts were equivalent. The serum erythropoietin levels during daprodustat administration were within the physiological range (8.5-18.8 mIU/mL). For anemia treatment in hemodialysis patients, daprodustat is less influenced by the inflammatory status than darbepoetin alfa, and one of the possible reasons for this includes the extended red blood cell lifespan.

The Role of Eryptosis in the Pathogenesis of Renal Anemia: Insights From Basic Research and Mathematical Modeling

Red blood cells (RBC) are the most abundant cells in the blood. Despite powerful defense systems against chemical and mechanical stressors, their life span is limited to about 120 days in healthy humans and further shortened in patients with kidney failure. Changes in the cell membrane potential and cation permeability trigger a cascade of events that lead to exposure of phosphatidylserine on the outer leaflet of the RBC membrane. The translocation of phosphatidylserine is an important step in a process that eventually results in eryptosis, the programmed death of an RBC. The regulation of eryptosis is complex and involves several cellular pathways, such as the regulation of non-selective cation channels. Increased cytosolic calcium concentration results in scramblase and floppase activation, exposing phosphatidylserine on the cell surface, leading to early clearance of RBCs from the circulation by phagocytic cells. While eryptosis is physiologically meaningful to recycle iron and other RBC constituents in healthy subjects, it is augmented under pathological conditions, such as kidney failure. In chronic kidney disease (CKD) patients, the number of eryptotic RBC is significantly increased, resulting in a shortened RBC life span that further compounds renal anemia. In CKD patients, uremic toxins, oxidative stress, hypoxemia, and inflammation contribute to the increased eryptosis rate. Eryptosis may have an impact on renal anemia, and depending on the degree of shortened RBC life span, the administration of erythropoiesis-stimulating agents is often insufficient to attain desired hemoglobin target levels. The goal of this review is to indicate the importance of eryptosis as a process closely related to life span reduction, aggravating renal anemia.

Prediction of hemoglobin levels in individual hemodialysis patients by means of a mathematical model of erythropoiesis

Anemia commonly occurs in people with chronic kidney disease (CKD) and is associated with poor clinical outcomes. The management of patients with anemia in CKD is challenging, due to its severity, frequent hypo-responsiveness to treatment with erythropoiesis stimulating agents (ESA) and common hemoglobin cycling. Nonlinear dose-response curves and long delays in the effect of treatment on red blood cell population size complicate predictions of hemoglobin (Hgb) levels in individual patients. A comprehensive physiology based mathematical model for erythropoiesis was adapted individually to 60 hemodialysis patients treated with ESAs by identifying physiologically meaningful key model parameters from temporal Hgb data. Crit-Line^® III monitors provided non-invasive Hgb measurements for every hemodialysis treatment. We used Hgb data during a 150-day baseline period together to estimate a patient’s individual red blood cell lifespan, effects of the ESA on proliferation of red cell progenitor cells, endogenous erythropoietin production and ESA half-life. Estimated patient specific parameters showed excellent alignment with previously conducted clinical studies in hemodialysis patients. Further, the model qualitatively and quantitatively reflected empirical hemoglobin dynamics in demographically, anthropometrically and clinically diverse patients and accurately predicted the Hgb response to ESA therapy in individual patients for up to 21 weeks. The findings suggest that estimated model parameters can be used as a proxy for parameters that are clinically very difficult to quantify. The presented method has the potential to provide new insights into the individual pathophysiology of renal anemia and its association with clinical outcomes and can potentially be used to guide personalized anemia treatment.

Regulation of blood volume in lowlanders exposed to high altitude

Humans ascending to high altitude (HA) experience a reduction in arterial oxyhemoglobin saturation and, as a result, arterial O₂ content ([Formula: see text]). As HA exposure extends, this reduction in [Formula: see text] is counteracted by an increase in arterial hemoglobin concentration. Initially, hemoconcentration is exclusively related to a reduction in plasma volume (PV), whereas after several weeks a progressive expansion in total red blood cell volume (RCV) contributes, although often to a modest extent. Since the decrease in PV is more rapid and usually more pronounced than the expansion in RCV, at least during the first weeks of exposure, a reduction in circulating blood volume is common at HA. Although the regulation of hematological responses to HA has been investigated for decades, it remains incompletely understood. This is not only related to the large number of mechanisms that could be involved and the complexity of their interplay but also to the difficulty of conducting comprehensive experiments in the often secluded HA environment. In this review, we present our understanding of the kinetics, the mechanisms and the physiological relevance of the HA-induced reduction in PV and expansion in RCV.

Erythropoietin reduces storage lesions and decreases apoptosis indices in blood bank red blood cells

Background

Recent evidence shows a selective destruction of the youngest circulating red blood cells (neocytolysis) trigged by a drop in erythropoietin levels.

Objective

The aim of this study was to evaluate the effect of recombinant human erythropoietin beta on the red blood cell storage lesion and apoptosis indices under blood bank conditions.

Methods

Each one of ten red blood cell units preserved in additive solution 5 was divided in two volumes of 100 mL and assigned to one of two groups: erythropoietin (addition of 665 IU of recombinant human erythropoietin) and control (isotonic buffer solution was added). The pharmacokinetic parameters of erythropoietin were estimated and the following parameters were measured weekly, for six weeks: Immunoreactive erythropoietin, hemolysis, percentage of non-discocytes, adenosine triphosphate, glucose, lactate, lactate dehydrogenase, and annexin-V/esterase activity. The t-test or Wilcoxon's test was used for statistical analysis with significance being set for a p-value <0.05.

Results

Erythropoietin, when added to red blood cell units, has a half-life >6 weeks under blood bank conditions, with persistent supernatant concentrations of erythropoietin during the entire storage period. Adenosine triphosphate was higher in the Erythropoietin Group in Week 6 (4.19 ± 0.05 μmol/L vs. 3.53 ± 0.02 μmol/L; p-value = 0.009). The number of viable cells in the Erythropoietin Group was higher than in the Control Group (77% ± 3.8% vs. 71% ± 2.3%; p-value <0.05), while the number of apoptotic cells was lower (9.4% ± 0.3% vs. 22% ± 0.8%; p-value <0.05).

Conclusions

Under standard blood bank conditions, an important proportion of red blood cells satisfy the criteria of apoptosis. Recombinant human erythropoietin beta seems to improve storage lesion parameters and mitigate apoptosis.

HIF-mediated increased ROS from reduced mitophagy and decreased catalase causes neocytolysis

During prolonged hypoxia, hypoxia-inducible factors (HIFs) mediate an increase in erythropoiesis, leading to an increased red blood cell (RBC) mass and polycythemia. Upon return to normoxia, the increased RBC mass is abruptly overcorrected by the preferential destruction of hypoxia-formed young RBCs, a phenomenon termed neocytolysis. The molecular and biochemical mechanisms involved in neocytolysis are unknown. We developed a murine model of neocytolysis by exposing mice to 12 % oxygen for 10 days followed by return to normoxia. Upon return to normoxia, there was excessive accumulation of reactive oxygen species (ROS) in RBCs from an increased reticulocyte mitochondrial mass correlating with decreased Bnip3L transcripts (Bnip3L mediates reticulocyte mitophagy) and reduced catalase activity. During hypoxia, upregulated miR-21 resulted in low catalase activity in young RBCs. Furthermore, neocytolysis was attenuated by antioxidants and plasma catalase and blunted in mice that had constitutively high expression of HIFs. Among human neonates studied, we report data supporting the existence of neocytolysis during the first week of life. Together, these experiments indicate that the major mechanisms causing neocytolysis involve (1) production of young RBCs with low catalase during hypoxia and (2) lysis of the young RBCs after return to normoxia, mediated by ROS from an increased mitochondrial mass.

KEY MESSAGES

We report a mouse model of neocytolysis. Neocytolysis is caused by excessive ROS formation mediated by HIF. ROS is generated from increased mitochondria in reticulocytes. Hypoxia-generated RBCs have low catalase and are preferentially destroyed. Reduced catalase is regulated by increased microRNA-21.

Twice-monthly administration of a lower dose of epoetin beta pegol can maintain adequate hemoglobin levels in hemodialysis patients

Epoetin beta pegol is a continuous erythropoietin receptor activator (CERA) with a long half-life. Although CERA has been shown to maintain adequate hemoglobin (Hb) levels at prolonged dosing intervals, the optimal dosing schedule remains unclear. We therefore compared the efficacy of maintaining hemoglobin levels with administration of twice-monthly CERA (TWICE) versus once-monthly CERA (ONCE). Twenty hemodialysis patients receiving epoetin beta (EPO) were enrolled in this crossover study. Patients were assigned to either the TWICE or the ONCE group based on matching Hb levels and EPO doses. After 6 months of treatment, the CERA dosage was interchanged between the groups and the study was continued for an additional 6 months. The effect of the different regimens on iron metabolism was also assessed during the first 6 months of the study. Hb levels significantly increased in the TWICE group, allowing for a reduction in CERA dosage, while the dose of CERA required to maintain Hb levels in the ONCE group remained unchanged. After the interchange, a decrease in Hb levels with incremental increase in CERA dosage was observed in the TWICE→ONCE group, with the opposite effect observed in the ONCE→TWICE group. Although increases in ferritin and hepcidin-25 levels in the ONCE group were noted at one month, they disappeared at 6 months. Although Hb levels were maintained in both the ONCE and TWICE groups, a twice-monthly administration was advantageous, as it required a lower dose of CERA.

The quantification of reticulocyte maturation and neocytolysis in normal and erythropoietin stimulated rats

A technique has recently been proposed for obtaining the reticulocyte (RET) age distribution from the flow cytometric reticulocyte count. It allows for a quantitative characterization of reticulocyte dynamics. In this work this technique was applied to characterize the blood, bone marrow and spleen reticulocytes in homeostatic and erythropoietically stimulated rats in order to determine the reticulocyte maturation times in the bone marrow and blood; and to confirm the presence of ineffective erythropoiesis (neocytolysis). The latter was done by comparing the reticulocyte removal rate from blood with bilirubin formation after erythropoiesis stimulation. A single subcutaneous dose (4050 IU/kg) of recombinant human erythropoietin (rHuEPO) was administered to rats, then their reticulocytes were stained with thiazole orange and the distribution of the fluorescent signal measured using flow cytometry. The obtained signal distribution of the reticulocytes was transformed to the age distribution and a set of basic parameters reflecting reticulocyte dynamics was determined. Bilirubin concentrations were measured to directly assess the presence of reticulocyte irreversible removal. The bilirubin formation was found to be considerably modulated by rHuEPO and corresponded well to the determined reticulocyte removal rate. The initial increase and subsequent decrease of the reticulocyte maturation time in blood was quantitated and directly linked with RET mobilization from the bone marrow. A substantial number (60%) of reticulocytes is sequestrated during homeostasis in rats. This number increases and then decreases after rHuEPO administration, as also reflected by bilirubin formation. Flow cytometry seems to be an excellent method for studying RET dynamics and the presence of young RBC neocytolysis.

Neocytolysis: none, one or many? A reappraisal and future perspectives

Neocytolysis is the hypothesis formulated to explain experimental evidence of selective lysis of young red blood cells (RBCs) (neocytes) associated with decreased plasma levels of erythropoietin (EPO). In humans, it appears to take place whenever a fast RBC mass reduction is required, i.e., in astronauts during the first days of spaceflight under weightlessness, where a fast reduction in plasma volume and increase in haematocrit occur. EPO plasma levels then decline and a decrease in RBC mass takes place, apparently because of the selective lysis of the youngest, recently generated RBCs (neocytes). The same process seems to occur in people descending to sea level after acclimatization at high altitude. After descent, the polycythaemia developed at high altitude must be abrogated, and a rapid reduction in the number of circulating RBCs is obtained by a decrease in EPO synthesis and the lysis of what seem to be young RBCs. In vivo, neocytolysis seems to be abolished by EPO administration. More recent research has ascribed to neocytolysis the RBC destruction that occurs under such disparate pathophysiologic conditions as nephropathy, severe obstructive pulmonary disease, blood doping, and even malaria anaemia. According to the theory, EPO's central role would be not only to stimulate the production of new RBCs in conditions of anaemia, as maintained by the orthodox view, but also that of a cytoprotective factor for circulating young RBCs. Why neocytes are specifically destroyed and how is this related to decreased EPO levels has not yet been elucidated. Changes in membrane molecules of young RBCs isolated from astronauts or mountain climbers upon return to normal conditions seem to indicate a higher susceptibility of neocytes to ingestion by macrophages. By limiting the context to space missions and high altitude expeditions, this review will address unresolved and critical issues that in our opinion have not been sufficiently highlighted in previous works.

A model of erythropoiesis in adults with sufficient iron availability

In this paper we present a model for erythropoiesis under the basic assumption that sufficient iron availability is guaranteed. An extension of the model including a sub-model for the iron dynamics in the body is topic of present research efforts. The model gives excellent results for a number of important situations: recovery of the red blood cell mass after blood donation, adaptation of the number of red blood cells to changes in the altitude of residence and, most important, the reaction of the body to different administration regimens of erythropoiesis stimulating agents, as for instance in the case of pre-surgical administration of Epoetin-α. The simulation results concerning the last item show that choosing an appropriate administration regimen can reduce the total amount of the administered drug considerably. The core of the model consists of structured population equations for the different cell populations which are considered. A key feature of the model is the incorporation of neocytolysis.

Facility-level interpatient hemoglobin variability in hemodialysis centers participating in the Dialysis Outcomes and Practice Patterns Study (DOPPS): Associations with mortality, patient characteristics, and facility practices

BACKGROUND

Hemodialysis patients with larger hemoglobin level fluctuations have higher mortality rates. We describe facility-level interpatient hemoglobin variability, its relation to patient mortality, and factors associated with facility-level hemoglobin variability or achieving hemoglobin levels of 10.5-12.0 g/dL. Facility-level hemoglobin variability may reflect within-patient hemoglobin variability and facility-level anemia-control practices.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

Data from the Dialysis Outcomes and Practice Patterns Study (DOPPS; 26,510 hemodialysis patients, 930 facilities, 12 countries, 1996-2008) and from the Centers for Medicare & Medicaid Services (CMS; 193,291 hemodialysis patients, 3,741 US facilities, 2002).

PREDICTORS

Standard deviation (SD) in single-measurement hemoglobin levels in hemodialysis patients in facility cross-sections (facility-level hemoglobin SD); patient characteristics; facility practices.

OUTCOMES

Patient-level mortality; additionally, facility practices correlated with facility-level hemoglobin SD or patient hemoglobin levels of 10.5-12.0 g/dL.

RESULTS

Facility-level hemoglobin SD varied more than 5-fold across DOPPS facilities (range, 0.5-2.7 g/dL; mean, 1.3 g/dL) and by country (range, 1.1 in Japan-DOPPS [2005/2006] to 1.7 g/dL in Spain-DOPPS [1998/1999]), with substantial decreases seen in many countries from 1998 to 2007. Facility-level hemoglobin SD was related inversely to patient age, but was associated minimally with more than 30 other patient characteristics and facility mean hemoglobin levels. Several anemia management practices were associated strongly with facility-level hemoglobin SD and having a hemoglobin level of 10.5-12.0 g/dL. When examined in CMS data, facility-level hemoglobin SD was positively associated with within-patient hemoglobin SD during the prior 6 months. Patient mortality rates were higher with greater facility-level hemoglobin SD (DOPPS: HR, 1.08 per 0.5-g/dL greater facility-level hemoglobin SD [95% CI, 1.02-1.15; P = 0.006]; CMS: HR, 1.16 per 0.5-g/dL greater facility-level hemoglobin SD [95% CI, 1.11-1.21; P < 0. 001]).

LIMITATIONS

Residual confounding.

CONCLUSIONS

Facility-level hemoglobin SD was associated strongly and positively with patient mortality, not tightly linked to numerous patient characteristics, but related strongly to facility anemia management practices. Facility-level hemoglobin variability may be modifiable and its optimization may improve hemodialysis patient survival.

Functional NMDA receptors in rat erythrocytes

N-methyl-d-aspartate (NMDA) receptors are ligand-gated nonselective cation channels mediating fast neuronal transmission and long-term potentiation in the central nervous system. These channels have a 10-fold higher permeability for Ca2+compared with Na+or K+and binding of the agonists (glutamate, homocysteine, homocysteic acid, NMDA) triggers Ca2+uptake. The present study demonstrates the presence of NMDA receptors in rat erythrocytes. The receptors are most abundant in both erythroid precursor cells and immature red blood cells, reticulocytes. Treatment of erythrocytes with NMDA receptor agonists leads to a rapid increase in intracellular Ca2+resulting in a transient shrinkage via Gardos channel activation. Additionally, the exposure of erythrocytes to NMDA receptor agonists causes activation of the nitric oxide (NO) synthase facilitating either NO production in l-arginine-containing medium or superoxide anion (O2·−) generation in the absence of l-arginine. Conversely, treatment with an NMDA receptor antagonist MK-80, or the removal of Ca2+from the incubation medium causes suppression of Ca2+accumulation and prevents attendant changes in cell volume and NO/O2·−production. These results suggest that the NMDA receptor activity in circulating erythrocytes is regulated by the plasma concentrations of homocysteine and homocysteic acid. Moreover, receptor hyperactivation may contribute to an increased incidence of thrombosis during hyperhomocysteinemia.

Discovery and basic pharmacology of erythropoiesis-stimulating agents (ESAs), including the hyperglycosylated ESA, darbepoetin alfa: an update of the rationale and clinical impact

Cloning of the human erythropoietin (EPO) gene and development of the first recombinant human erythropoietin (rHuEPO) drug were truly breakthroughs. This allowed a deeper understanding of the structure and pharmacology of rHuEpo, which in turn inspired the discovery and development of additional erythropoiesis-stimulating agents (ESAs). In vivo specific activity and serum half-life of rHuEPO are influenced by the amount and structure of the attached carbohydrate. Increased numbers of sialic acids on carbohydrate attached to rHuEPO correlated with a relative increase in in-vivo-specific activity and increased serum half-life. The effect of increasing the number of sialic-acid-containing carbohydrates on in-vivo-specific activity was explored. Initial research focused on solving the problem of how the protein backbone could be engineered so a cell would add more carbohydrate to it. Additional work resulted in darbepoetin alfa, a longer-acting molecule with two additional carbohydrate chains.

Inflammation and its impact on anaemia in chronic kidney disease: from haemoglobin variability to hyporesponsiveness

The availability of erythropoiesis-stimulating agents (ESAs) has revolutionized the treatment of anaemia in patients with chronic kidney disease. However, maintaining patients at haemoglobin (Hb) levels that are both safe and provide maximal benefit is a continuing challenge in the field. Based on emerging data on the potential risks of Hb treatment targets >13 g/dL, treatment targets have recently been lowered. In the latest revision (March 2008) of the European product labelling for the ESA class of drugs, the target treatment range was lowered to 10–12 g/dL. Fluctuation of Hb levels or ‘Hb variability’ during treatment with ESAs is a well-documented phenomenon. Hb levels that are either too high or too low may have an adverse effect on patient outcomes; thus, it is important to understand the causes of Hb variability in order to achieve optimal treatment. Several factors are believed to contribute to variation in the Hb level, including patient comorbidities and intercurrent events. Inflammation is also an important factor associated with Hb variability, and the consequences of persistent inflammatory activity are far-reaching in affected patients. This review addresses the complex role of inflammation in chronic kidney disease, as evidenced by the apparent state of deranged inflammatory markers. The mechanisms by which inflammatory cytokines may affect the response to ESAs, the development of anaemia and poor treatment outcomes are also examined. In addition, various options for intervention to enhance the response to ESAs in haemodialysis patients with inflammation are considered.

[Hemoglobin variability in chronic renal failure patients]

In recent years, the question of hemoglobin (Hb) stability in patients with chronic renal failure has attracted the interest of medical experts. One of the most important reasons behind this interest is that maintaining the hemoglobin level within the new narrower target range is highly challenging in clinical practice. According to the results available from observational trials, instability of inter-patient hemoglobin levels may be associated with increased morbidity and mortality. To clarify the questions and answers related to this topic and to prepare an updated summary, we reviewed the scientific literature. With the help of the PubMed portal, the incidence, clinical importance, and reasons of Hb variability were summarized according to the available scientific literature. Hb variability is affected by multiple factors which are connected to the general condition of the patient as well as medical interventions and treatments. Also the fluctuation of serum Hb level is a physiological process and is a healthy sign of the capability of the normal human body to adapt. The characteristics and extent of Hb variability vary in patients with chronic renal failure and this topic requires further clinical research. More precise studies are needed in order to explore the differences in possible Hb variability as well as the change in variability caused by particular treatment methods. Finally, based on the available data, the results of future research, and on board scientific consensus, in a strategy for treatment of renal anemia, we should take into account the questions related to Hb stability and variability.

Stem cells and nuclear reprogramming

Derivation of human embryonic stem (ES) cells from preimplantation embryos ten years ago raised great hopes that they may be an excellent source of cells for cell replacement therapy. However, serious ethical concerns and the risk of immune rejection of allotransplanted cells have hindered the translation of ES cell-based therapies into the clinic. In an attempt to circumvent these barriers, a number of methods have been developed for converting adult somatic cells into a pluripotent state from which ethically acceptable patient-specific mature cells of interest could be derived. These efforts, backed by advances in elucidating the molecular basis of pluripotency, have culminated in successful reprogramming of fibroblasts into ES cell-like cells, termed induced pluripotent stem (iPS) cells, by ectopic expression of only a handful of "stemness" factors. iPS cells possess morphological, molecular and developmental features of conventional blastocyst-derived ES cells and have the potential to serve as a source of therapeutic cells for customized tissue repair, gene therapy, drug discovery, toxicological testing and for studying the molecular basis of human disease. The goal of this review is to provide the current state-of-the-art in this very exciting and dynamic field and to discuss barriers that remain to be removed before the therapeutic potential of iPS cells can be fully realized.

Serum albumin is strongly associated with erythropoietin sensitivity in hemodialysis patients

BACKGROUND AND OBJECTIVES

In hemodialysis patients, the hematological response to erythropoietin (epo) is variable and clinical factors that explain this variability are incompletely understood. We tested the hypothesis that the variability in hemoglobin (Hgb) response (epo sensitivity) is determined by key nutritional, inflammation, and oxidative stress markers.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Eighty-two consecutive patients on hemodialysis had 3 consecutive monthly predialysis evaluations of Hgb, total white blood cell (WBC) count, serum albumin, malondialdehyde (MDA), and monocyte chemoattractant protein-1 (MCP1). We analyzed the time course of Hgb in relationship to serum albumin, WBC, MDA, MCP1, epo and iron administration, and tests of iron sufficiency in a linear growth curve model.

RESULTS

Subjects with higher Hgb had a fall in Hgb and vice versa, regressing to a mean Hgb (SD) of 11.8 g/dl (1.8 g/dl). Whereas the average slope of Hgb was flat, the SD of slopes was 0.63 g/dl, which explained 39% of the variance in Hgb. Nonuse of epo was associated with a mean Hgb change of -0.18 g/dl (95% confidence interval [CI] -0.26 to -0.10) per 10,000 IU epo/mo (P < 0.05). Epo use was associated with steeper rate of change at 0.04 g/dl per mo per 10,000 IU (95% CI 0.01 to 0.07) (P < 0.01). Hgb at baseline was 0.73 g/dl higher for each 1-g/dl increase in albumin, and the rate of change increased by 0.49 g/dl per mo for each 1-g/dl increase in albumin concentration. WBC, MDA, or MCP1 had no role in predicting the baseline Hgb or its change over time.

CONCLUSIONS

Serum albumin concentration is an important predictor of both baseline Hgb and epo sensitivity in chronic hemodialysis patients. Factors that improve serum albumin may also improve Hgb in hemodialysis patients.