For the study, Winkelmayer's team looked at how ESAs were used in about 4,500 dialysis centers across the United States, analyzing data from people treated with ESAs and intravenous iron. They then looked at one-year death rates among the centers' patients.
The researchers found that people with the most severe anemia, with a hematocrit of less than 30 percent, benefited most from aggressive treatment with ESAs, while those with less severe anemia did not. The lower the hematocrit, the more anemic the person.
Less anemic people, those with hematocrits greater than 36 percent, had an 11 percent higher risk for dying if they received aggressive ESA treatment than did similar people whose anemia was treated less aggressively. Among those with hematocrits of 30 percent and 36 percent, aggressive or non-aggressive treatment with ESAs had no effect on mortality, the researchers found.
The findings for treatment with intravenous iron were the same as those for ESAs, Winkelmayer said. Centers that used more aggressive treatment with intravenous iron at low hematocrit had better outcomes, and more aggressive iron use among people with relatively higher hematocrit was associated with more deaths, he noted.
Anemia is a common complication of kidney disease. There are three ESAs sold in the United States to treat anemia: darbepoetin alfa, marketed by Amgen as Aranesp, and epoetin alfa, marketed by Amgen as Epogen and by Johnson & Johnson as Procrit.
ESAs were introduced in 1989, but safety questions have come to light that have brought their use into question. For example, the drugs were promoted as a way to counter the debilitating effects of chemotherapy, but studies have found that the drugs can cause tumors to grow faster, shortening people's lives.
In cancer patients, the drugs are now mostly used as palliative ca
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