DENVER—Serum phosphate and fibroblast growth factor 23 (FGF-23) levels increase in incident peritoneal dialysis (PD) patients increase as residual renal function declines, according to researchers.

Liesbeth Viaene, MD, of University Hospital in Leuven, Belgium, studied 35 PD patients (19 male). Midday blood samples were collected and analyzed. The investigators determined residual glomerular filtration rate (rGFR) as the arithmetic mean of renal urea nitrogen and creatinine clearance.

At month 1, 6, 12, and 24, median rGFR values (mL/min/1.73 m2) were 5.3, 4.5, 3.8, and 2.4, respectively. Serum phosphate (mg/dL) values were 4.1, 4.7, 4.3, and 4.7, respectively. FGF-23 levels (ng/L) were 718 in month 1 and 1,516 at month 24. For all of these parameters, the differences between month 2 and month 24 were statistically significant.

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Whether the increasing FGF-23 levels are a direct consequence of the ailing kidney and/or secondary to increased phosphate levels remains to be investigated.