Table 1.

Baseline characteristics of participants by category of plasma FGF23 concentration

CharacteristicaOverall CohortFGF23<100 RU/mlFGF23=100–169 RU/mlFGF23≥170 RU/ml
n587238189160
Age, yr12 (8–15)11 (9–15)12 (8–15)12 (8–15)
Female, %38353941
Race/ethnicity, %
 White70677370
 Black14151213
 Other17181617
Systolic BP z-score0.27 (−0.48 to 0.94)0.25 (−0.53 to 0.88)0.26 (−0.45 to 0.93)0.34 (−0.35 to 1.12)
Nonglomerular CKD, %78798173
Duration of CKD, yr9.1 (5.3–13.1)9.0 (5.3–12.5)9.1 (5.4–13.5)9.5 (5.2–13.0)
eGFR, ml/min per 1.73 m250 (38–64)60 (47–75)50 (39–61)39 (27–50)b
Body mass index, kg/m218.8 (16.6–22.6)19.1 (16.9–23.2)18.7 (16.4–22.8)18.5 (16.4–21.5)
Height z-score−0.6 (−1.3 to 0.2)−0.4 (−1.2 to 0.3)−0.7 (−1.3 to 0.2)−0.7 (1.4 to −0.01)c
Serum albumin, g/dl4.4 (4.1–4.6)4.5 (4.3–4.7)4.3 (4.1–4.6)4.3 (4.0–4.5)b
Hemoglobin z-score−0.62 (−1.95 to 0.55)−0.16 (−1.33 to 0.77)−0.70 (−1.88 to 0.62)−1.56 (−2.81 to −0.18)b
Mineral metabolism
 Serum calcium, mg/dl9.2 (9.0–9.5)9.2 (8.9–9.5)9.3 (9.0–9.5)9.3 (9.0–9.6)c
 Serum phosphorus, mg/dl4.4 (4.0–4.9)4.4 (3.9–4.7)4.4 (4.0–4.8)4.6 (4.0–5.2)d
 Phosphorus z-score−0.3 (−1.1 to 0.6)−0.4 (−1.3 to 0.3)−0.3 (−1.1 to 0.5)0.0 (−0.9 to 1.2)d
 Serum 25OHD, ng/ml28 (21–35)27 (21–35)28 (22–36)28 (17–35)
 Serum 1,25(OH)D, pg/ml33 (25–41)36 (27–42)34 (26–41)29 (22–35)b
 Serum iPTH, pg/ml48 (32–73)39 (26–55)59 (40–83)69 (42–141)d
Urine protein-to-creatinine ratio, mg/mg0.3 (0.1–1.0)0.2 (0.1–0.5)0.4 (0.1–0.9)0.7 (0.2–1.7)d
Medication use
ACEI/ARB, %54565254
Active vitamin D sterols, %30163149b
Nutritional vitamin D supplements, %40294154b
Phosphate-binding agents, %17121526d
  • FGF23, fibroblast growth factor 23; 25OHD, 25-hydroxyvitamin D; 1,25(OH)D, 1,25-dihydroxyvitamin D; iPTH, intact parathyroid hormone; ACEI, angiotensin-converting enzyme inhibitors; ARB, angiotensin-receptor blockers.

  • a Median (interquartile range) reported for continuous characteristics; percentage reported for categorical characteristics.

  • b P<0.001 versus FGF23<100 RU/ml.

  • c P<0.05 versus FGF23<100 RU/ml.

  • d P<0.01 versus FGF23<100 RU/ml.