Abstract
Background: Fibroblast Growth Factor 23 (FGF-23) and α-Klotho contribute to the patho-genesis of chronic kidney disease - mineral and bone disorders (CKD-MBD). The aim of our study was to evaluate the association of FGF-23 and α-Klotho levels with CKD-MBD parameters, as well as with renal prognosis and mortality, in CKD patients stage 1-5, not in renal replacement therapy (RRT).
Methods: 128 patients were included. At enrollment GFR was measured (mGFR) and plasma levels of carboxyl terminal FGF-23 (cFGF-23) and soluble α-Klotho (sKlotho) were determined by ELISA. Abdominal aorta calcification (AAC) score was assessed in lateral abdominal X ray. The composite end point (event) was initiation of RRT or death. Follow-up was five years (median 36, range 2-60 months).
Results: mGFR significantly correlated with cFGF-23 and sKlotho negatively and posi-tievely respectively (p<0.0001 for both). Multiple regression analysis showed an inde-pendent correlation of cFGF-23 with mGFR, 25-OH vitamin D, presence of diabetes melli-tus and AAC score, of sKlotho with mGFR and phosphate and of AAC score with sKlotho and cFGF-23. Multivariate regression tree analysis, led to the formation of three regression groups (A, B, C) based on two “cut off” values: mGFR levels of 60.85 ml/min/1.73m2 and serum phosphate levels of 3.7 mg/dl. These groups significantly correlated with the five CKD stages and additionally cFGF-23 and sKlotho plasma levels (p<0.0001 for both). During follow-up, 40 out of the 128 patients, (31.2%) either initiated RRT or died (31 and 9 respectively). Kaplan Meier survival analysis showed that groups of patients with cFGF-23 levels less than median and those with sKlotho more than median value showing a more favorable course, regarding outcome (p=0.0003 for cFGF-23, p=0.004 for s-Klotho). In Cox regression analysis the association of cFGF-23 (p=0.04), sKlotho (p=0.008) and AAC score (p=0.01) with the presence of “event” remained significant after adjustment for traditional and CKD- related covariates.
Conclusions: In CKD patients stage 1-5, cFGF-23 and sKlotho levels are associated with adverse clinical outcomes. mGFR and serum phosphate, in association with sKlotho lev-els, may provide a “new classification” of CKD patients, which appears to be predictive of outcome.
The Urinary Phosphate to Serum Fibroblast Growth Factor 23 Ratio, Deemed the Nephron Index, Is a Useful Clinical Index for Early Stage Chronic Kidney Disease in Patients with Type 2 Diabetes: An Observational Pilot Study