Table 1.

Baseline characteristics of 503 incident hemodialysis participants of the Choices for Healthy Outcomes in Caring for ESRD Study by tertiles of serum β-trace protein

NSerum β-Trace Protein Tertiles (range, mg/L)Linear Trend P Value
Lowest Tertile (1.8–6.1)Middle Tertile (6.1–8.8)Highest Tertile (8.8–21.1)
Number of participants503168168167
Serum β-trace protein (mg/L)a503
 mean (SD)4.6 (1.0)7.3 (0.8)11.4 (2.5)
 median (25th to 75th percentiles)4.8 (3.8–5.5)7.3 (6.7–7.9)10.8 (9.8–12.2)
 median time from dialysis initiation to specimen collection (months; 25th to 75th percentiles)4.5 (3.5–5.9)4.8 (3.8–6.0)5.1 (4.1–6.2)0.003
Demographic
 age50359 (14)57 (15)58 (15)0.54
 sex (percent female)5035242430.15
 race (percent white)5036468590.26
 education (percent high school graduate)4893733330.60
 employment (percent working)503111260.15
 marital status (percent married)5035249470.65
Clinical
 smoking status (percent ever smoker)4895659610.64
 index of coexistent disease score (percent)5020.33
  ≤1332531
  2384244
  3293325
 baseline comorbid conditions (%)
  diabetes5025960520.27
  CVD5025655550.97
  CHF5025049480.91
  LVH5022923290.35
 BMI median (kg/m2; 25th to 75th percentiles)47527.2 (22.7–32.1)25.9 (22.8–31.0)25.0 (21.9–28.3)0.001
 systolic BP (mmHg)484149 (19)153 (17)152 (18)0.10
 diastolic BP (mmHg)48478 (10)81 (10)81 (10)0.03
 pulse pressure (mmHg)48471 (15)73 (13)72 (14)0.59
 urine output≥1 cup/d
  status at baseline (percent yes)4879087750.001
  status at year 1425<0.001
   not at baseline or year 1 (%)111528
   at baseline but not year 1 (loss of RKF; %)524952
   at baseline and year 1 (preserved RKF; %)373620
 urine volume (ml)231<0.001
  mean (SD)906 (584)815 (548)605 (381)
  median (25th to 75th percentiles)738 (500–1150)600 (400–1100)525 (300–800)
ESRD-related
 eGFR at dialysis initiation (ml/min per 1.73 m2)b47611 (4)10 (3)9 (4)<0.001
 assigned primary cause of renal failure (%)503<0.001
  diabetes505543
  hypertension181123
  glomerulonephritis101322
 late referral (%; <4 months)3129310.62
 average dialysis Kt/Vc4001.37 (0.28)1.31 (0.26)1.39 (0.27)0.42
 average dialysis duration in minutes434216 (23)218 (23)219 (22)0.18
Laboratory
 predialysis BUN (mg/dl)40457 (14)59 (15)61 (15)0.02
 predialysis creatinine (mg/dl)5016.6 (2.0)8.2 (2.4)9.8 (3.1)<0.001
 potassium (mEq/L)5004.6 (0.6)4.7 (0.6)4.9 (0.6)<0.001
 albumin (g/dl)5033.4 (0.6)3.5 (0.5)3.7 (0.6)<0.001
 calcium (mg/dl)5009.8 (0.7)9.8 (0.9)9.7 (0.8)0.56
 phosphorus (mg/dl)5005.1 (1.3)5.8 (1.5)5.9 (1.7)<0.001
 hemoglobin (g/dl)50010.9 (1.1)11.2 (1.1)10.9 (1.1)0.48
 C-reactive protein (mg/dl; median [25th to 75th percentiles])5020.63 (0.30–1.39)0.58 (0.25–1.42)0.64 (0.22–1.70)0.77
Baseline medications
 diuretics (%)5033029240.38
 ACE inhibitors (%)5032830290.89
 calcium channel blockers (%)5036057680.07
β-blockers (%)5032723240.66
 phosphate binders (%)5038890930.24
 EPO dose (units/wk)d33842,184 (25,024)47,388 (24,157)48,956 (26,621)0.06
  • Numbers presented are mean (SD) or percent unless otherwise specified. Conversion factors for units: albumin in g/dl to g/L, ×10; calcium in mg/dl to mmol/L, ×0.2495; phosphorus in mg/dl to mmol/L, ×0.3229; hemoglobin in g/dl to g/L, ×10; BUN in mg/dl to urea in mmol/L, ×0.357; creatinine in mg/dl to umol/L, ×88.4. No conversion is necessary for potassium in mEq/L to mmol/L. CVD, cardiovascular disease; CHF, congestive heart failure; LVH, left ventricular hypertrophy; BMI, body mass index; RKF, residual kidney function; eGFR, estimated GFR; ACE, angiotensin converting enzyme; EPO, erythropoietin.

  • a Normal reference range of serum BTP has not been determined. In the Atherosclerosis Risk in Communities Study, among those individuals in the highest eGFR group (>96.7 ml/min per 1.73 m2), serum β-trace protein (BTP) was 0.6±0.1 mg/L, and among those individuals in the lowest eGFR group (<60 ml/min per 1.73 m2), serum BTP was 1.1±0.9 mg/L (52).

  • b eGFR at dialysis initiation is eGFR at the time of initiation of renal replacement therapy. It is calculated using the four-variable Modification of Diet in Renal Disease Study formula from serum creatinine reported on Form 2728 (53).

  • c Dialysis dose (Kt/V) was calculated using the Daugirdas formula and was available for 327 (65%) participants at baseline (54).

  • d EPO dose is average weekly erythropoietin dose requirements during the first 6 months after enrollment.