Table 1.
Baseline characteristics of the study population by tertile of plasma FGF23 concentration
| Characteristic | Overall Cohort | Tertile 1 | Tertile 2 | Tertile 3 |
|---|---|---|---|---|
| FGF23, RU/ml | <100 | 100–169 | ≥170 | |
| n | 419 | 141 | 139 | 139 |
| Age, yr | 11.1 [7.8, 14.5] | 10.7 [7.4, 14.2] | 11.1 [7.7, 14.3] | 12.2 [8.2, 14.9] |
| Female, n (%) | 160 (38) | 52 (37) | 50 (36) | 58 (42) |
| Race, n (%) | ||||
| White | 292 (70) | 98 (70) | 95 (68) | 99 (71) |
| Black | 83 (20) | 31 (22) | 29 (21) | 23 (17) |
| Multiracial or other | 44 (11) | 12 (9) | 15 (11) | 17 (12) |
| Hispanic | 56 (14) | 27 (19) | 12 (9) | 17 (13) |
| Primary CKD diagnosis, n (%) | ||||
| Glomerular | 89 (21) | 27 (19) | 20 (14) | 42 (30) |
| Obstruction/reflux | 159 (38) | 55 (39) | 60 (43) | 44 (32) |
| Hypoplasia/dysplasia | 69 (16) | 20 (14) | 25 (18) | 24 (17) |
| Other nonglomerular | 83 (20) | 36 (26) | 26 (19) | 21 (15) |
| Cystic diseasea | 19 (5) | 3 (2) | 8 (6) | 8 (6) |
| Hypertensive, n (%) | 86 (21) | 22 (16) | 26 (19) | 38 (28) |
| GFR, ml/min per 1.73 m2 | 44 [33, 57] | 52 [41, 71] | 45 [35, 56]b | 35 [28, 47]b,c |
| Mineral metabolism | ||||
| Serum calcium, mg/dl | 9.4±0.4 | 9.4±0.4 | 9.4±0.4 | 9.4±0.5 |
| Serum phosphorus, mg/dl | 4.6±0.8 | 4.4±0.6 | 4.6±0.8 | 4.7±0.9b |
| Serum phosphorus z-score | −0.1±1.5 | −0.4±1.2 | −0.1±1.4 | 0.3±1.7b,c |
| Serum iPTH, pg/mld | 54 [32, 97] | 39 [24, 55] | 62 [38, 108]b | 82 [44, 1454]b |
| Plasma FGF23, RU/ml | 132 [88, 200] | 75 [60, 88] | 133 [115, 149]b | 250 [200, 405]b,c |
| Serum 25OHD, ng/ml | 27±12 | 27±10 | 29±12 | 26±13 |
| Serum 1,25(OH)2D, pg/ml | 31±11 | 33±11 | 32±12 | 22±11b,c |
| Serum albumin, g/dl | 4.3±0.4 | 4.4±0.3 | 4.3±0.3 | 4.1±0.6b,c |
| Urine protein-to-creatinine ratio, mg/mg | 0.4 [0.2, 1.0] | 0.2 [0.1, 0.6] | 0.3 [0.1, 0.8] | 0.7 [0.3, 1.8]b,c |
| Medication use, n (%) | ||||
| Antihypertensive (ACE/ARB) | 227 (54) | 79 (56) | 72 (52) | 76 (55) |
| Phosphate binders | 86 (21) | 23 (16) | 24 (17) | 39 (28) |
| Active vitamin D | 155 (37) | 32 (23) | 46 (33) | 77 (55) |
| Nutritional vitamin D | 21 (5) | 8 (6) | 6 (4) | 7 (5) |
Data are means±SD, medians [25th, 75th percentile] or n (%). FGF23, fibroblast growth factor; iPTH, immunoreactive parathyroid hormone; 25OHD, 25-hydroxyvitamin D; 1,25(OH)2D, 1,25-dihydroxyvitamin D; ACE, angiotensin converting enzyme; ARB, angiotensin receptor blocker.
a
Recessive polycystic kidney disease (n=13), juvenile nephronophthisis (n=4), dominant polycystic kidney disease (n=2).
b
P<0.05 versus tertile 1.
c
P<0.05 versus tertile 2.
d
n=219.