Utility of Testing Fibroblast Growth Factor 23 in Patients with Chronic Kidney Disease: A Single Center Experience

Introduction: Disordered phosphate homeostasis with elevated circulating levels of fibroblast growth factor 23 (FGF-23) is an early complication of CKD leading to different types of bone diseases. Treatment strategies are designed to keep calcium, phosphate, parathyroid hormone (PTH) and vitamin D within defined ranges for patients with these bone diseases. Presently, FGF 23 is not included into standard treatment protocols for management of bone diseases in CKD.

Objective: Primary Objective: The primary objective of the study was to compare and correlate FGF 23 levels in patients with CKD with calcium, phosphorus, vitamin D and parathyroid hormone levels.

Secondary Objectives: 1) To determine association between haemoglobin level and corresponding FGF 23 level in patients with CKD in different stages.

2) To study variations in FGF 23 levels in high and low turnover bone disease.

Methods: We examined the working hypothesis that FGF-23 is an indicator of CKD progression and related bone diseases. We examined if its appearance is earlier than other parameters like calcium, phosphate, PTH and vitamin D in CKD progression. To understand ‘off target’ effects of FGF-23 we included the presence of anaemia as an additional parameter. We attempted to study variations in FGF 23 level in high and low turnover bone diseases and effects of phosphate binders on FGF 23 in these two types of bone diseases.

It was an observational open label prospective study conducted in 2015-16 at Care Hospitals, Hyderabad, India. It included all adult patients with CKD selected sequentially.

Results: A Kruskal Wallis test was run on 64 samples showed statistically no significant difference of FGF23 between different stages of CKD. There was a statistically significant difference in haemoglobin levels among different stages of CKD. FGF 23 levels were higher in patients with high turnover type of bone disorder but Wilcoxon Mann Whitney test results indicated no statistical significance. The chi-square test results indicated that there was a statistically significant effect of phosphate binders on FGF 23 levels.

Conclusions: FGF-23 and haemoglobin correlated inversely in a subgroup analysis of high and low turnover bone diseases. FGF 23 was lower in low turnover disease and higher in high turnover bone disease. Although this correlation was statistically insignificant, FGF 23 may differentiate high and low turnover bone disease. Serum intact FGF-23 levels did not correlate statistically with progression of CKD. The effect of phosphate binders on lowering FGF-23 levels was statistically significant.