Table 1.

Clinical characteristics of the cohort

VariableAll Patients
(n=593)Plasma FGF23 Tertiles
Tertile 1 (n=197)Tertile 2 (n=198)Tertile 3 (n=198)P Value
Plasma C-terminal FGF23 (RU/ml)140 (95–219)83 (68–96)141 (124–162)311 (220–567)<0.001
Age (yr)52±1250±1352±1253±110.04
Men (%)545651550.62
Whites (%)959494950.41
Cause of kidney disease (%)0.75
 Primary GN28263029
 GN due to vasculitis/autoimmune disease6956
 Tubulointerstitial nephritis/pyelonephritis16201514
 Polycystic kidney disease18161820
 Hypertension6755
 Diabetes3433
 Other/unknown23182423
Dialysis duration (mo)27 (13–48)24 (13–43)31 (14–48)26 (13–52)0.40
Deceased donor transplant (%)86789291<0.001
Cold ischemia time (h)22 (15–27)20 (7–27)22 (16–26)22 (16–29)0.04
Total warm ischemia time (min)35 (30–45)35 (30–45)35 (30–45)36 (30–45)0.92
Total HLA mismatches (n)1 (0–2)1 (0–2)1 (0–2)1 (0–2)0.41
History of acute rejection (%)453944520.04
Transplant vintage (yr)6.1 (2.7–11.7)5.6 (2.4–11.1)5.8 (3.0–11.5)7.2 (3.5–12.2)0.06
Waist circumference (cm)97±1494±1397±14100±13<0.001
Systolic BP (mmHg)153±23148±21153±22157±25<0.001
Diastolic BP (mmHg)90±1089±1089±991±10<0.001
Current smoker (%)22181830<0.001
Current diabetes (%)181917180.88
Laboratory results
 Measurements in serum/plasma
  Creatinine (mg/dl)1.5 (1.3–1.9)1.4 (1.1–1.6)1.5 (1.3–1.7)1.9 (1.4–2.5)<0.001
  Albumin (g/dl)4.1±0.34.1±0.34.1±0.44.0±0.3<0.001
  Calcium (mg/dl)9.6±0.69.5±0.69.6±0.79.6±0.70.20
  Total cholesterol (mg/dl)218±42214±35219±38221±510.13
  HDL cholesterol (mg/dl)42±1245±1342±1240±12<0.001
  LDL cholesterol (mg/dl)137±39137±31136±39138±460.84
  NT-proBNP (pg/ml)299 (131–672)180 (92–419)285 (130–567)457 (240–1517)<0.001
  MR-proANP (pmol/L)164 (103–275)126 (87–188)153 (100–231)257 (158–390)<0.001
  Copeptin (pmol/L)9.3 (5.0–19.5)6.5 (3.8–10.4)8.6 (4.7–17.4)16.1 (7.7–30.0)<0.001
  C-reactive protein (mg/L)2.1 (0.8–4.9)1.7 (0.6–3.7)2.1 (0.8–4.5)3.0 (1.2–7.8)<0.001
  Glucose (mg/dl)87±2386±2287±2688±200.59
  Phosphate (mg/dl)3.3±0.73.1±0.63.2±0.63.6±0.7<0.001
  Parathyroid hormone (pg/ml)86 (57–131)72 (51–112)88 (61–121)101 (68–193)<0.001
  25-OH vitamin D (ng/ml)21±922±1021±822±100.49
  1,25-OH2 vitamin D (pg/ml)42±1847±1742±1935±15<0.001
  Hemoglobin (g/dl)13.7±1.514.2±1.313.8±1.313.1±1.7<0.001
  Estimated GFR (CKD-EPI) (ml/min per 1.73 m2)47±1655±1348±1437±15<0.001
 Measurements in 24-hour urine
  Sodium excretion (mEq/24 hr)140±68139±68138±61143±750.66
  Phosphate excretion (g/24 hr)2.3±0.82.3±0.92.4±0.82.2±0.80.18
  Proteinuria (g/24 hr)0.2 (0.0–0.5)0.2 (0.0–0.3)0.2 (0.0–0.4)0.3 (0.2–0.8)<0.001
  Urea excretion (g/24 hr)10.5±3.210.6±3.110.9±3.210.0±3.20.03
Medication
 Calcium supplements (%)756100.07
 Active vitamin D (alfacalcidol or calcitriol) (%)985140.02
 ACE inhibitor or ARB (%)343034390.17
 Prednisone dose (mg/d)10 (7.5–10)10 (7.5–10)10 (7.5–10)10 (7.5–10)0.58
 Calcineurin inhibitor (%)787783750.12
 Azathioprine (%)342934380.17
 Mycophenolate mofetil (%)40494131<0.001
 Sirolimus (%)22220.88
  • Values expressed with a plus/minus sign are the mean ± SD; values with parentheses are median and interquartile range. All variables were determined at enrollment except sex, race, cause of the original kidney disease, cold ischemia time, total warm ischemia time, and total number of HLA mismatches, which were assessed at time of transplantation. FGF23, fibroblast growth factor 23; NT-proBNP, N-terminal-pro brain natriuretic peptide; MR-proANP, pro–A-type natriuretic peptide; CKD-EPI, CKD-Epidemiology Collaboration; ACE, angiotensin-converting enzyme; ARB, angiotensin receptor blocker.