Table 1 Characteristics of study population

Plasma PTH (pmol/l)

9.9 [6.7-15.5]

6.5 [3.6-11.0]

<0.001

PTH exceeding recommended levels

67 (66%)

34 (34%)

<0.001

Age (years)

52.2 (12.7)

58.8 (11.8)

<0.001

Male sex

68 (67%)

75 (75%)

0.23

Caucasian race

99 (98%)

93 (93%)

0.09

Cause of kidney disease

<0.001

 Glomerulonephritis

34 (34%)

17 (17%)

 Diabetic nephropathy

9 (9%)

4 (4%)

 Renovascular

4 (4%)

15 (15%)

 Interstitial nephritis

25 (25%)

6 (6%)

 Congenital (including PKD)

20 (20%)

5 (5%)

 Different/unknown

9 (9%)

53 (53%)

Kidney transplant recipient

33 (33%)

9 (9%)

<0.001

History of diabetes mellitus

20 (20%)

13 (13%)

0.19

Income (euros/month)

2108 (489)

2030 (482)

0.26

BMI (kg/m²)

27.0 (5.0)

28.6 (4.5)

0.01

Smoking

15 (15%)

19 (19%)

0.43

Serum calcium (mmol/l)

2.40 (0.13)

2.40 (0.12)

0.71

Serum phosphate (mmol/l)

1.06 (0.25)

1.01 (0.22)

0.15

Serum urea (mmol/l)

13.5 [10.1-17.6]

9.8 [7.2-15.2]

<0.001

Serum albumin (g/l)

39 (4)

42 (3)

<0.001

Proteinuria (g/24 h)

0.6 [0.1-1.3]

0.3 [0.2-0.9]

0.10

Serum creatinine (μmol/l)

168 (53)

184 (60)

0.05

eGFR (MDRD-4, ml/min/1.73 m²)

40.3 (12.4)

36.3 (11.1)

0.02

Alphacalcidol use

16 (16%)

13 (13%)

0.57

Calciumcarbonate use

13 (13%)

5 (5%)

0.05

Alphacalcidol and/or calciumcarbonate use

21 (21%)

16 (16%)

0.38

Furosemide use

17 (17%)

9 (9%)

0.10

Thiazide use

22 (22%)

46 (46%)

<0.001

Number of drugs

5.82 (3.90)

5.73 (2.85)

0.85

Season of blood draw

0.34

 Winter

21 (21%)

15 (15%)

 Spring

24 (24%)

17 (17%)

 Summer

24 (24%)

30 (30%)

 Fall

32 (32%)

38 (38%)