FGF23 and anemia (phenotype): Compared to subjects without anemia, those with anemia had a lower median (IQR) eGFR (32 [21, 44] vs. 51 [40, 65] ml/min/1.73 m2, p < 0.001), a higher median phosphate SDS for age (−0.5 [−1.3, 0.7] vs. −0.8 [−1.5, −0.2], p < 0.001), a higher median total FGF23 concentration (204 [124, 390] vs. 109 [77, 168] RU/ml, p < 0.001), and a higher median total FGF23 SDS for age (3.5 [1.6, 6.6] vs. 1.3 [0.4, 2.8], p < 0.001) (Table 2).