Scatter plots and bivariate correlations for trough serum phosphate. The CKD subgroup is represented by black circles (•) while the non-CKD subgroup is represented by white circles (○). Pearson correlation coefficients were performed separately for all subjects combined, CKD only and non-CKD subgroups. iFGF23 was natural log transformed before analysis. PO₄, phosphate; FE_Pi, fractional excretion of phosphate; FCM/kg, weight adjusted ferric carboxymaltose dose; iFGF23, intact fibroblast growth factor 23.