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Topic Name: Researchers measure new anemia, predicts risk of death in dialysis patients

Category: Biomedical

Research persons: Dr. Harold I. Feldman

Location: University of Pennsylvania School of Medicine, Philadelphia, United States

Details

A new indicator of variations in hemoglobin level over time is a strong predictor of the risk of death among patients receiving dialysis for end-stage renal disease (ESRD), reports a study in the December Journal of the American Society of Nephrology.

"Hemoglobin variability—a measure of the stability of levels of hemoglobin among chronic hemodialysis patients—provides a novel way of thinking about and understanding the relationship between anemia and outcomes in ESRD," comments Dr. Harold I. Feldman of University of Pennsylvania School of Medicine, Philadelphia, one of the study authors.

The researchers used data on nearly 35,000 dialysis patients to analyze the effects of hemoglobin variability on the risk of death. They focused on a newly developed metric, termed “Hb-Var,” that measures variability in hemoglobin levels independent of their absolute values and trends over time.

Hemoglobin is the oxygen-carrying compound in the blood. Anemia, or low hemoglobin levels, is one of the most frequent complications of kidney failure and a common cause of death in dialysis patients. Treatment including erythropoietin and intravenous iron has been a major advance in the management of kidney failure-related anemia, yet low blood counts and variation in hemoglobin levels continue to be a problem for many dialysis patients.

The new study found that high Hb-Var scores—indicating greater hemoglobin variability—predicted a higher risk of death in dialysis patients. For each 1 g/dL (gram per deciliter) increase in Hb-Var, the risk of death increased by 33 percent, after adjustment for other factors.

The relationship between Hb-Var and mortality remained significant even after adjustment for absolute hemoglobin levels and trends in hemoglobin levels over time. Higher Hb-Var scores predicted an increased risk of death in nearly all subgroups of dialysis patients. "As postulated, higher levels of hemoglobin variability were associated with higher rates of death," says Dr. Feldman.

In healthy people, hemoglobin levels typically remain within a narrow range, ensuring consistent delivery of oxygen to organs and tissues. In dialysis patients, repeated drops in hemoglobin levels—and thus in the ability to deliver adequate levels of oxygen—may result in injury to organs. The heart muscle (myocardium) and autonomic nervous system may be especially vulnerable, which may help to explain the increased rates of cardiovascular disease and death in ESRD patients.

The new study identifies Hb-Var as a potentially valuable measure of the effects of low hemoglobin in ESRD, and lends new insights into how anemia affects outcomes in dialysis patients. Dr. Feldman concludes, "These findings may ultimately lead to health care practice changes regarding the management of anemia—for example, the type, dose, and timing of treatment with erythropoietin and iron—that might improve outcomes among hemodialysis patients."

The study entitled, "Hemoglobin Variability and Mortality in ESRD" will be available online at www.asn-online.org under Media, 2007, beginning on Wednesday, November 14 and in print in the December issue of the Journal of the American Society of Nephrology. 

Support for this study was provided by an unrestricted grant from Hoffman-La Roche Company.

The ASN is a not-for-profit organization of 10,500 physicians and scientists dedicated to the study of nephrology and committed to providing a forum for the promulgation of information regarding the latest research and clinical findings on kidney diseases.

Note for Hemoglobin

Hemoglobin, also spelled haemoglobin and abbreviated Hb, is the iron-containing oxygen-transport metalloprotein in the red blood cells of the blood in vertebrates and other animals. In mammals the protein makes up about 97% of the red cell’s dry content, and around 35% of the total content (including water). Hemoglobin transports oxygen from the lungs or gills to the rest of the body, such as to the muscles, where it releases its load of oxygen. Hemoglobin also has a variety of other gas-transport and effect-modulation duties, which vary from species to species, and may be quite diverse in invertebrates.

The name hemoglobin is the concatenation of heme and globin, reflecting the fact that each subunit of hemoglobin is a globular protein with an embedded heme (or haem) group; each heme group contains an iron atom, and this is responsible for the binding of oxygen through ion-induced dipole forces.

Note for Anemia

Anemia (AmE) or anæmia/anaemia (BrE),  is a deficiency of red blood cells (RBCs) and/or hemoglobin. This results in a reduced ability of blood to transfer oxygen to the tissues, causing tissue hypoxia. Since all human cells depend on oxygen for survival, varying degrees of anemia can have a wide range of clinical consequences. Hemoglobin (the oxygen-carrying protein in the red blood cells) has to be present to ensure adequate oxygenation of all tissues and organs. The three main classes of anemia include excessive blood loss (acutely such as a hemorrhage or chronically through low-volume loss), excessive blood cell destruction (hemolysis) or deficient red blood cell production (ineffective hematopoiesis). In menstruating women, dietary iron deficiency is a common cause of deficient red blood cell production.

Note for Cardiovascular disease

Cardiovascular disease refers to the class of diseases that involve the heart or blood vessels (arteries and veins). While the term technically refers to any disease that affects the cardiovascular system, it is usually used to refer to those related to atherosclerosis (arterial disease). These conditions have similar causes, mechanisms, and treatments. In practice, cardiovascular disease is treated by cardiologists, thoracic surgeons, vascular surgeons, neurologists, and interventional radiologists, depending on the organ system that is being treated. There is considerable overlap in the specialties, and it is common for certain procedures to be performed by different types of specialists in the same hospital.

Note for hemodialysis

In medicine, hemodialysis (also haemodialysis) is a method for removing waste products such as potassium and urea, as well as free water from the blood when the kidneys are incapable of this (i.e. in renal failure). It is a form of renal dialysis and is therefore a renal replacement therapy.

Hemodialysis is typically conducted in an dedicated facility, either a special room in a hospital or a clinic (with specialized nurses and technicians) that specializes in hemodialysis. Although less typical, dialysis can also be done in a patient's home as home hemodialysis.

About Researcher

Dr. Harold I. Feldman, Associate Professor of Medicine and Epidemiology, University of Pennsylvania Medical Center, 423 Service Drive, 923 Blockley Hall, Philadelphia, PA 19104–6021. Phone: 215-898-0901; Fax: 215-898-0643; 
E-mail: hfeldman@cceb.med.upenn.edu

About F. Hoffmann–La Roche

F. Hoffmann–La Roche, Ltd. is a Swiss global health-care company which operates world-wide under two divisions: Pharmaceuticals and Diagnostics. It belongs to the Roche Holding AG.
The headquarters are in Basel and the company has many sites around the world - including: Nutley, Palo Alto, Pleasanton, Branchburg, Indianapolis, Florence in the US, Welwyn Garden City in the UK, Mannheim, Penzberg in Germany, and Shanghai in China.
The company also owns a majority of the American biotechnology company Genentech and the Japanese biotechnology company Chugai Pharmaceuticals.
Roche Holding AG (ticker ROC.S) is listed on the London-based virt-x stock exchange (virt-x is a company of the SWX Swiss Exchange). Roche's revenues during fiscal year 2005 were $28.6 billion (2005, 35.5bn CHF). Descendants of the founding Hoffmann and Oeri families own half of the company. Swiss pharma company Novartis owns 33% of the company (as of 2005).