Background. High levels of the phosphaturic hormone fibroblast growth factor 23 (FGF-23) predict mortality in haemodialysis patients. The prognostic relevance of increased plasma FGF-23 levels in patients with less advanced chronic kidney disease (CKD) who are not on dialysis therapy is presently unknown.

Methods. We measured plasma c-terminal FGF-23 levels in 149 CKD patients not undergoing dialysis treatment. Patients were stratified by their baseline FGF-23 levels (>104 vs ≤104 rU/mL) and followed for a period of 4.8 ± 0.9 years. During the follow-up, the pre-specified combined clinical endpoint was the first occurrence of a cardiovascular event, e.g. myocardial infarction, coronary artery angioplasty/stenting/bypass surgery, stroke, carotid endarterectomy/stenting, non-traumatic lower extremity amputation, lower limb artery surgery/angioplasty/stenting or death.

Results. At baseline, elevated FGF-23 levels >104 rU/mL were associated with more advanced CKD. Traditional cardiovascular risk factors and prevalent cardiovascular disease did not differ between CKD patients with high vs low FGF-23 levels. Fifty patients experienced a cardiovascular event during follow-up. Compared with CKD patients with FGF-23 ≤104 rU/mL, CKD patients with FGF-23 levels above the cut-off had worse event-free survival at univariate (log-rank test P = 0.012) and multivariate analysis [hazard ratio 2.49 (95% CI 1.40–4.39); P = 0.002].

Conclusions. Elevated FGF-23 plasma levels predict cardiovascular events in CKD patients not on dialysis therapy. This finding complements two recent cohort studies in which incident and prevalent haemodialysis patients with highest FGF-23 levels had worst survival. Lowering FGF-23 levels (e.g. by oral phosphate binder medication) could emerge as a promising new therapeutic option to reduce cardiovascular morbidity in CKD patients.