Fibroblast Growth Factor Indicates Death Risk in Dialysis Patients

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Title: Fibroblast Growth Factor Indicates Death Risk in Dialysis Patients
URL: http://www.pslgroup.com/dg/22743E.htm
Doctor's Guide
August 6, 2008

BOSTON -- August 6, 2008 -- Monitoring levels of fibroblast growth factor 23 (FGF-23) may provide information crucial to the treatment of patients with kidney failure, according to a study in the August 7 issue of the New England Journal of Medicine.

Patients with elevated levels of FGF-23 when beginning haemodialysis had a significantly increased risk of death within the first year of treatment, regardless of whether they had other risk factors.

The study also found evidence that FGF-23 levels may differ between racial groups, which may relate to observed disparities in survival of dialysis patients.

"FGF-23 helps regulate serum phosphate levels. And we know that, among patients with kidney failure, elevated phosphate is associated with more rapid progression to renal failure and earlier death," said lead author Myles Wolf, MD, formerly with Massachusetts General Hospital Renal Unit, Boston, Massachusetts, and currently with the University of Miami Miller School of Medicine, Miami, Florida.

"The results of this study suggest that we need to be concerned about phosphate control even for patients whose serum phosphate levels are normal, and that may involve routine screening for FGF-23."

Researchers analysed levels of both phosphate and FGF-23 in over 10,000 patients who began dialysis at more than 1,000 centres across North America. They examined the relationship between phosphate levels and the risk of death within the year after dialysis began and confirmed that mortality was modestly higher in those with the highest phosphate levels.

They then compared serum FGF-23 levels of 200 patients who died during that first year with the levels of 200 patients who survived. To ensure that the effects of FGF-23 could be analysed separately from those of phosphate, those 400 patients were selected to be equally balanced across the spectrum of serum phosphate levels.

Elevated FGF-23 levels proved to be a much more powerful predictor of death than serum phosphate measured at the same time. Among those with the highest FGF-23 levels, the mortality rate was 600% higher than in patients with the lowest levels, while patients with the highest phosphate levels had only a 20% elevation of risk.

In addition, intermediate FGF-23 levels reflected an intermediate risk of death, an association not seen for phosphate levels. Even among patients with normal phosphate levels, elevated FGF-23 significantly increased the risk of death.

The data also showed that FGF-23 levels tended to be lower among black and Hispanic patients, something not reported in previous FGF-23 studies that primarily enrolled white and Asian patients.

Black patients with the lowest FGF-23 levels had an even lower risk of death compared with white patients with similar levels, which echoes previous observations of a reduced mortality rate among black dialysis patients.

"This is the first report of racial and ethnic differences in FGF-23 levels, and we are now investigating whether such differences are also seen in healthy patients and in those with earlier stages of kidney disease," said Dr. Wolf.

"Incorporating FGF-23 levels into the management of kidney failure may have its greatest potential for treatment of the millions of patients with early-stage kidney disease who do not yet require dialysis, who usually have normal phosphate levels but quite high FGF-23," he adds.

"Routinely monitoring of FGF-23 may help determine which patients need to begin therapies that control phosphate levels, which may reduce mortality in this very high risk group."

SOURCE: Massachusetts General Hospital

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