FGF23 Doesn’t Predict Outcomes in Patients with Low-Risk Stage 3 CKD, Study Finds

In primary care patients with stage 3 chronic kidney disease (CKD), low vitamin D and high parathyroid hormone (PTH) are predictors of increased mortality—but high fibroblast growth factor 23 (FGF23) is not, reports a study in BMJ Open.

Vitamin D deficiency, PTH, and elevated fibroblast growth factor 23 (FGF23) have all been associated with increased mortality in individuals with chronic kidney disease (CKD).

Noting that previous studies focused only on the effects of FGF23 in relatively advanced CKD, Adam Shardlow, of the Royal Derby Hospital Renal Medicine Department, and his colleagues set out to determine whether FGF23 is also a risk factor in people with early CKD, and to assess how this risk compares to the risk associated with vitamin D deficiency or elevated PTH.

Shardlow and his colleagues conducted a prospective cohort study of 1664 patients meeting KDIGO criteria for stage 3 CKD, drawn from 32 UK general practices. Participants were predominantly older, with a mean age of 73 years, and had a low risk of progression of their kidney disease. About 60% of patients were women. Fibroblast growth factor 23, PTH, and vitamin D were evaluated as risk factors for mortality or for CKD progression over 5 years of follow-up.

At baseline, 29% of patients had elevated FGF23 (> 51 pg/mL). Twenty-five percent of patients had elevated PTH (> 65 pg/mL), 6.3% had vitamin D deficiency, and 38.9% had vitamin D insufficiency. During follow-up, 18.9% of patients died from any cause, and 17.4% had progression of CKD.

Mortality was higher for patients with elevated FGF23, elevated PTH, and vitamin D deficiency and insufficiency. In adjusted analyses, vitamin D deficiency and elevated PTH remained significant risk factors for mortality, with a hazard ratio of 1.62 and 1.42, respectively.

In contrast, FGF23 was not an independent predictor of death on multivariable analysis. None of the three markers was significantly associated with risk of CKD progression. Few patients in the primary care sample had progression to end stage renal disease.

“While FGF23 may have a role as a risk marker in high-risk populations managed in secondary care, our data suggest that it may not be as important in CKD stage 3, managed in primary care,” the authors write.

References

1. Shardlow A, et al. Associations of fibroblast growth factor 23, vitamin D and parathyroid hormone with 5-year outcomes in a prospective primary care cohort of people with chronic kidney disease stage 3. BMJ Open. 2017; [http://dx.doi.org/10.1136/bmjopen-2017-016528].

October/November 2017 (Vol. 9, Number 10 & 11)