Synthetic hormone may boost heart risks in kidney patients
The increasingly common practice of using a synthetic form of the hormone EPO to maintain normal red blood cell levels in chronic kidney disease patients may increase cardiovascular risks, according to a study published today in the New England Journal of Medicine.
The study of 1,432 patients in the U.S. found that those who had undergone the treatment had a 34% increased risk of heart attack, congestive heart failure, stroke and death, according to the study.
Researchers said a safer course for patients would be to boost red blood cells to only slightly below normal.
An accompanying study of 603 patients in Europe found no increased risk, but neither did it find any benefit from using higher doses of EPO.
Low red blood cell levels, or anemia, is a common complication of chronic kidney disease, which affects about 10 million people in the U.S.
Damaged kidneys don’t make enough erythropoietin, a hormone needed to produce red blood cells.
Red blood cells carry oxygen to muscles, including cardiac muscle. So people with severe anemia become easily tired and face higher heart attack risk.
Anemia is often diagnosed by measuring levels of the blood protein hemoglobin.
A normal hemoglobin level, depending on age and gender, is generally considered around 13 grams per deciliter of blood.
To counteract the anemia, patients are typically given regular injections of synthetic erythropoietin, or EPO.
The Food and Drug Administration has approved using EPO to maintain between 11 and 12 grams of hemoglobin per deciliter of blood in kidney disease patients.
But several small studies have shown that patients feel better and have more energy at higher hemoglobin levels, and that has led physicians to use higher doses of EPO.
One-fifth of the 500,000 kidney dialysis patients in the U.S. now receive EPO treatments to maintain their hemoglobin at 13 grams or higher, according to government statistics.
The latest studies, one conducted in the U.S. and the other in Europe, set out to determine whether higher hemoglobin levels were really healthier for patients.
The U.S. study, led by researchers at Harvard Medical School, found an increased risk of serious complications in patients with a hemoglobin level of 13.5 grams, compared to patients with a level of 11.3 grams. The study was paid for by Johnson & Johnson, which markets EPO in the U.S.
The European study found no difference in risk between patients with “normal” hemoglobin -- defined in the study as 13 to 15 grams -- and mildly anemic patients with hemoglobin of 11 to 12.5 grams.
The study was sponsored by Roche, which markets EPO in Europe.
Researchers were puzzled by the result. They said it was possible that EPO increased the viscosity of patients’ blood, straining the cardiovascular system.
An editorial in the journal said the findings of both studies indicated that doctors should refrain from trying to boost red blood cell levels to normal.
The nonprofit National Kidney Foundation expanded its guidelines last spring to allow for more aggressive treatment of anemia.
The organization said it would review its treatment guides in light of the new research.
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