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Phosphorus Binders Associated With Lower Mortality in Dialysis Patients

WASHINGTON, DC -- December 16, 2008 -- Patients on dialysis who are taking phosphorus binders may also be reducing their risk of death by 25% to 30%, according to a study being published early online and appearing in the February 2009 issue of the Journal of the American Society of Nephrology.

Phosphorus binders are associated with improved survival in new dialysis patients, including those patients with only modest or even no increase in their blood phosphorus levels.

"This important finding suggests that perhaps treatment with phosphorus binders should be extended back to patients with less severe chronic kidney disease (CKD)," said coauthor Myles Wolf, MD, University of Miami, Miami, Florida. "This is a much larger population of patients, virtually all of whom have near-normal blood levels of phosphorus but a markedly increased risk of premature death."

The researchers compared mortality rates in 2 groups of dialysis patients: 3,555 patients who started treatment with phosphorus binders during the first 90 days after starting dialysis and 5,055 who did not receive treatment during the same period.

During the first year on dialysis, patients treated with phosphorus binders had a 30% lower risk of death, even after adjusting for other risk factors.

A further analysis compared mortality rates in a large subgroup of treated and untreated patients, who were closely matched in terms of their initial blood phosphorus levels and their likelihood of receiving phosphorus binders. In this "propensity score-matched" analysis, risk of death was 25% lower in patients treated with phosphorus binders. The protective effect of phosphorus binders was smaller, but still significant, in an analysis that excluded patients who died in the first 90 days on dialysis.

"Because hyperphosphatemia is a risk factor for death, phosphorus binders are widely prescribed to dialysis patients," said Dr. Wolf. "Nephrologists have assumed that this treatment strategy will improve the clinical outcomes of our patients, such that the target range for serum phosphate levels in dialysis patients has been lowered in recent years."

But, "whether treatment with any dietary phosphorus binders versus no treatment would improve survival had never been studied until now," he said.

If phosphorus binders improve survival even in new dialysis patients with relatively normal phosphorus levels, then it is possible that they might also be beneficial for the much larger group of patients with less advanced kidney disease.

"These patients are typically not considered for treatment with phosphorus binders," said Dr. Wolf. If further studies could demonstrate a similar survival benefit of binders in patients with predialysis CKD, the results could have a significant impact on the public health."

The study has some important limitations. Since it was not a randomised trial, it is prone to certain forms of bias and confounding. Other limitations include the limited, 1-year follow-up; the lack of data on patients' dietary phosphorus intake; and whether they actually took their prescribed phosphorus binders.

SOURCE: American Society of Nephrology

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