Table 1 Baseline characteristics of the study population by CKD stagea.

From: Lower serum calcium is independently associated with CKD progression

 

All (n = 15,755)

CKD 3a (n = 9,286)

CKD 3b (n = 4,190)

CKD 4 (n = 1,784)

CKD 5 (n = 495)

Age (years)

79.9 (70.2–85.8)

79.0 (69.8–85.1)

81.9 (73.5–87.2)

80.1 (68.2–86.4)

73.2 (61.6–82.4)

Sex (% men)

6,140 (39.0)

3,323 (35.8)

1,676 (40.0)

841 (47.1)

300 (60.6)

Comorbidities (%) b

Diabetes mellitus

2,352 (14.9)

1,012 (10.9)

723 (17.3)

480 (26.9)

137 (27.7)

Cardiovascular disease

1,502 (9.5)

722 (7.8)

479 (11.4)

251 (14.1)

50 (10.1)

Hypertension

9,794 (62.2)

5,035 (54.4)

2,981 (71.1)

1,411 (79.1)

399 (80.6)

Corrected calcium (mg/dl)∗

9.5 ± 0.5

9.5 ± 0.5

9.6 ± 0.5

9.5 ± 0.6

9.6 ± 0.9

Hypercalcemia (>10.2 mg/dl)

1,165 (7.4)

560 (6.0)

371 (8.9)

161 (9.0)

73 (14.7)

Hypocalcemia (<8.6 mg/dl)

179 (1.1)

63 (0.7)

34 (0.8)

46 (2.6)

36 (7.3)

Vitamin D use (%) c

55 (30.7)

4 (6.3)

6 (17.6)

19 (41.3)

26 (72.2)

Active vitamin D use (%) c

1 (0.6)

0 (0.0)

0 (0.0)

0 (0.0)

1 (2.8)

Albumin corrected calcium (mg/dl) ∗

9.6 ± 0.5

9.6 ± 0.5

9.6 ± 0.5

9.6 ± 0.6

9.7 ± 0.8

Serum albumin (g/l) ∗

37.0 ± 4.1

37.5 ± 3.8

36.6 ± 4.1

35.8 ± 4.5

35.4 ± 4.8

Albuminuria (% yes) d

720 (4.6)

270 (2.9)

205 (4.9)

167 (9.4)

78 (15.8)

Baseline eGFR (ml/min/1.73 m 2 )

48.1 (37.2–55.0)

53.9 (49.9–57.2)

38.8 (34.9–42.2)

24.4 (20.3–27.5)

11.0 (8.5–13.1)

Number of repeated eGFR tests

5.0 (2.0–13.0)

4.0 (1.0–10.0)

6.0 (2.0–13.0)

9.0 (4.0–17.0)

8.0 (4.0–15.8)

Phosphorus (mg/dl) ∗

3.7 ± 0.9

3.4 ± 0.6

3.5 ± 0.7

3.9 ± 0.8

5.1 ± 1.3

iPTH (pg/ml)*

143.8 ± 144.6

72.8 ± 49.1

104.0 ± 67.5

161.1 ± 125.5

270.2 ± 249.5

Serum Hb (g/l)

131.5 ± 16.0

134.7 ± 15.2

129.2 ± 15.7

123.8 ± 15.7

119.1 ± 16.5

Medication (%)

Calcium supplements

105 (0.7)

88 (0.9)

15 (0.4)

1 (0.1)

1 (0.2)

Bisphosphonates

836 (5.3)

537 (5.8)

240 (5.7)

51 (2.9)

8 (1.6)

Phosphate binders

313 (2.0)

9 (0.1)

40 (1.0)

112 (6.3)

152 (30.7)

Vitamin D therapy

915 (5.8)

99 (1.1)

175 (4.3)

366 (20.5)

275 (55.6)

Active vitamin D use

54 (0.3)

10 (0.1)

16 (0.4)

18 (1.0)

10 (2.0)

Diuretics

7,876 (50.0)

3,842 (41.4)

2,440 (58.2)

1,252 (70.2)

342 (69.1)

Thiazide diuretics

492 (3.1)

335 (3.6)

124 (3.0)

31 (1.7)

2 (0.4)

Loop diuretics

2,184 (13.9)

995 (10.7)

689 (16.4)

410 (23.0)

90 (18.2)

  1. aContinuous variables are expressed as mean ± standard deviation or median (interquartile range), and categorical variables are expressed as number (percentage).
  2. bComorbidities are deduced from Charlson domains. cThese numbers only apply to patients with hypocalcemia (<8.6 mg/dL).
  3. d% Albuminuria is presented as percentage of the total study population, instead of the percentage of the patient population in which an actual albuminuria test was performed. Due to the missingness, the percentages shown are an underestimation of the actual percentage of albuminuria in the study population.
  4. *To convert serum albumin in g/dl to g/l, multiply by 10; serum calcium in mg/dl to mmol/l, multiply by 0.2495; serum phosphorus in mg/dl to mmol/l, multiply by 0.3229; serum iPTH in pg/ml to ng/l, multiply by 1.
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