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Table 1 Baseline characteristic of CKD stages 3–4 patients according to quartiles of serum calcium level

From: Low serum calcium is associated with poor renal outcomes in chronic kidney disease stages 3–4 patients

   Quartile of serum calcium level (mg/dL)  
   Q1 Q2 Q3 Q4  
  All patients (<9.0) (9.0 - 9.4) (9.4 - 9.8) (>9.8) p for trend
No. of patients 2144 544 452 588 560 -
Demographic data       
Age, yrs 64.2 ± 13.5 64.1 ± 14.3 64.8 ± 13.7 63.8 ± 13.2 64.1 ± 13.0 0.636
Gender (female) 756 (35.3%) 179 (32.9%) 149 (33.0%) 207 (35.2%) 221 (39.5%) 0.017
Diabetes mellitus 940 (43.8%) 209 (38.4%) 184 (40.7%) 265 (45.1%) 282 (50.4%) <0.001
Cardiovascular disease 381 (17.8%) 101 (18.6%) 92 (20.4%) 94 (16.0%) 94 (16.8%) 0.197
Hypertension 1360 (63.4%) 386 (71.0%) 303 (67.0%) 364 (61.9%) 307 (54.8%) <0.001
Smoker (recent) 279 (13.0%) 70 (12.9%) 56 (12.4%) 78 (13.3%) 75 (13.4%) 0.711
Mean BP, mmHg 99.4 ± 13.5 97.9 ± 13.1 99.1 ± 12.9 100.5 ± 14.8 100.1 ± 12.7 0.002
Body mass index, kg/m2 25.0 ± 3.9 24.6 ± 3.8 25.2 ± 3.8 25.1 ± 4.1 25.3 ± 4.1 0.017
Laboratory results       
eGFR, ml/min/1.73 m2 33.2 ± 11.9 31.2 ± 11.8 33.4 ± 11.8 34.5 ± 11.8 33.5 ± 11.9 0.001
Hemoglobin, g/dL 11.9 ± 2.1 11.5 ± 2.0 12.1 ± 2.1 12.1 ± 2.1 12.0 ± 2.1 <0.001
Albumin, g/dL 3.9 ± 0.5 3.9 ± 0.4 3.9 ± 0.4 3.9 ± 0.5 3.8 ± 0.6 0.003
GPT, U/I 26.3 ± 25.1 24.4 ± 23.8 25.5 ± 24.6 27.1 ± 27.4 28.2 ± 24.0 0.006
Cholesterol, mg/dL 192.0 (165.0-223.5) 187.0 (160.0-213.0) 190.0 (163.0-217.8) 194.0 (168.8-224.0) 198.0 (167.6-232.8) <0.001
Triglyceride, mg/dL 127.0 (93.0-189.0) 117.0 (86.3-171.7) 123.0 (89.0-172.8) 134.0 (97.0-188.0) 141.0 (100.0-212.8) <0.001
WBC, x103/uL 7.2 ± 2.3 7.1 ± 2.4 7.1 ± 2.1 7.1 ± 2.1 7.5 ± 2.4 0.012
CRP, mg/dL; 1.0 (0.3-4.6) 1.1 (0.5-4.0) 1.0 (0.4-3.3) 0.9 (0.3-4.2) 1.2 (0.2-7.3) 0.993
HbA1c, mg/dL; 6.6 ± 1.7 6.4 ± 1.5 6.3 ± 1.4 6.7 ± 1.7 7.0 ± 1.8 <0.001
UPCR, mg/g 702.8 (263.0-1697.7) 800.7 (334.6-1778.8) 721.3 (269.9-1670.1) 615.6 (229.1-1698.2) 659.8 (244.9 - 1698.6) 0.016
Sodium, mEq/L 138.6 ± 3.4 138.2 ± 3.4 138.7 ± 3.1 138.9 ± 3.4 138.8 ± 3.6 0.003
Potassium, mEq/L 4.3 ± 0.5 4.3 ± 0.5 4.2 ± 0.5 4.3 ± 0.5 4.4 ± 0.5 <0.001
Phosphorus, mg/dL 3.9 ± 0.8 4.0 ± 0.9 3.9 ± 0.8 3.9 ± 0.8 3.9 ± 0.7 0.019
Calcium, mg/dL 9.2 ± 0.7 8.6 ± 0.5 9.1 ± 0.3 9.3 ± 0.3 10.0 ± 0.5 <0.001
Ca x Pi 36.2 ± 7.5 34.2 ± 7.4 35.1 ± 7.0 36.6 ± 7.5 38.5 ± 7.2 <0.001
PTH, pg/mL 68.4 ± 79.5 96.2 ± 105.8 66.3 ± 68.6 61.6 ± 72.2 50.4 ± 54.4 <0.001
Bicarbonate, mEq/L 23.4 ± 3.6 22.6 ± 3.8 23.6 ± 3.5 23.8 ± 3.5 23.8 ± 3.7 <0.001
Uric acid, mg/dL 7.8 ± 1.9 7.8 ± 1.9 7.7 ± 1.9 7.7 ± 1.8 7.8 ± 2.0 0.588
Phosphate binder 381 (17.8%) 105 (19.3%) 86 (19.0%) 92 (15.6%) 98 (17.5%) 0.129
Outcome       
Follow-up, days 1085(682–1673) 1061 (673–1608) 1059 (676–1575) 1092 (688–1686) 1191 (705–1749) 0.017
LVMI 118.5 (45.0) 129.2 (42.9) 121.9 (56.3) 112.3 (42.7) 114.1 (37.6) 0.037
eGFR slope, ml/min/1.73 m2/yr -1.9 (-5.4-0.5) -2.6 (-6.2-0.1) -1.7 (-4.7-0.5) -1.9 (-5.6-0.5) -1.4 (-4.9-1.1) <0.001
Rapid renal progression 574 (27.0%) 172 (31.9%) 115 (25.4%) 151 (25.7%) 136 (24.5%) 0.029
RRT 294 (13.7%) 107 (19.7%) 54 (11.9%) 73 (12.4%) 60 (10.7%) <0.001
Death 270 (12.6%) 56 (10.3%) 53 (11.7%) 65 (11.1%) 96 (17.1%) <0.001
  1. CKD, Chronic kidney disease; BP, Blood pressure; eGFR, Estimated glomerular filtration rate; GPT, Glutamic pyruvic transaminase; WBC, White blood cell count; CRP, C-reactive protein; HbA1c, Glycosylated hemoglobin; UPCR, Urine protein to creatinine ratio; Ca x Pi, Calcium phosphate product; PTH, Parathyroid hormone; RRT, Renal Replacement Therapy; LVMI, Left ventricular mass index; LVH, Left ventricular hypertrophy.
  2. Continuous variables are expressed as mean ± standard deviation or median (interquartile range), and categorical variables are expressed as number (percentage). P for trend <0.05 indicates a significant trend for increasing calcium levels.
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