Table 1.
Clinical characteristics of the study subjects at enrollment stratified by serum bicarbonate concentration.
| Characteristics | Total (N = 1,659) | Serum TCO2 | P-value | P for trend | |||
|---|---|---|---|---|---|---|---|
| Low (<22 mmol/L) (n = 210) | Lower normal (22–26 mmol/L) (n = 697) | Higher normal (26.1–29.9 mmol/L) (n = 524) | High (≥30 mmol/L) (n = 228) | ||||
| Total CO2 | 25.8 ± 3.6 | 19.6 ± 1.9 | 24.2 ± 1.3 | 27.9 ± 0.9 | 31.3 ± 1.4 | <0.001 | <0.001 |
| Age (mean ± SD) | 53.4 ± 12.4 | 54.2 ± 12.0 | 54.1 ± 12.5 | 52.5 ± 12.3 | 52.5 ± 12.5 | 0.069 | 0.063 |
| Sex, male, n (%) | 1,020 (61.5) | 125 (59.5) | 428 (61.4) | 317 (60.5) | 150 (65.8) | 0.504 | 0.288 |
| BMI (kg/m2) | 24.6 ± 3.5 | 24.0 ± 3.4 | 24.7 ± 3.4 | 24.6 ± 3.6 | 24.7 ± 3.2 | 0.067 | 0.048 |
| SBP (mmHg) | 127.5 ± 15.3 | 129.7 ± 18.0 | 127.1 ± 15.3 | 127.3 ± 14.8 | 127.4 ± 13.5 | 0.194 | 0.146 |
| DBP (mmHg) | 77.0 ± 10.9 | 77.0 ± 11.6 | 76.3 ± 10.7 | 77.8 ± 11.1 | 77.2 ± 10.2 | 0.145 | 0.519 |
| MAP (mmHg) | 93.8 ± 11.2 | 94.5 ± 12.3 | 93.3 ± 11.0 | 94.3 ± 11.3 | 93.9 ± 10.4 | 0.331 | 0.809 |
| Heart rate (/min) | 73.4 ± 12.9 | 73.4 ± 13.5 | 72.7 ± 12.6 | 74.5 ± 13.1 | 73.4 ± 12.7 | 0.121 | 0.595 |
| DM, n (%) | 574 (34.7) | 84 (40.0) | 259 (37.2) | 168 (32.1) | 63 (28.0) | 0.015 | 0.001 |
| HTN, n (%) | 1586 (95.7) | 206 (98.1) | 672 (96.6) | 495 (94.5) | 213 (93.4) | 0.031 | 0.003 |
| Preexisting CV disease, n (%) | 279 (16.8) | 56 (26.7) | 120 (17.2) | 77 (14.7) | 26 (11.4) | <0.001 | <0.001 |
| CAD, n (%) | 115 (7.0) | 26 (12.4) | 52 (7.5) | 27 (5.2) | 10 (4.4) | 0.002 | <0.001 |
| Cerebrovascular disease, n (%) | 113 (6.8) | 17 (8.1) | 52 (7.5) | 34 (6.5) | 10 (4.4) | 0.361 | 0.088 |
| HF, n (%) | 28 (1.7) | 10 (4.8) | 11 (1.6) | 6 (1.1) | 1 (0.4) | 0.002 | 0.001 |
| Arrhythmia, n (%) | 36 (2.2) | 10 (4.8) | 8 (1.1) | 13 (2.5) | 5 (2.2) | 0.016 | 0.187 |
| PVD, n (%) | 63 (3.8) | 12 (5.7) | 27 (3.9) | 18 (3.4) | 6 (2.6) | 0.368 | 0.101 |
| Cause of CKD | <0.001 | 0.229 | |||||
| DN, n (%) | 387 (23.3) | 61 (29.0) | 193 (27.7) | 104 (19.8) | 29 (12.7) | ||
| Hypertension, n (%) | 288 (17.4) | 45 (21.4) | 120 (17.2) | 87 (16.6) | 36 (15.8) | ||
| GN, n (%) | 565 (34.1) | 67 (31.9) | 228 (32.7) | 174 (33.2) | 96 (42.1) | ||
| PKD, n (%) | 311 (18.7) | 22 (10.5) | 111 (15.9) | 126 (24.0) | 52 (22.8) | ||
| Others, n (%) | 108 (6.5) | 15 (7.1) | 45 (6.5) | 33 (6.3) | 15 (6.6) | ||
| Smoking status, n (%) | 0.660 | 0.169 | |||||
| Never | 888 (53.5) | 109 (51.9) | 359 (51.5) | 292 (55.7) | 128 (56.1) | ||
| Former | 514 (31.0) | 70 (33.3) | 221 (31.7) | 153 (29.2) | 70 (30.7) | ||
| Current | 257 (15.5) | 31 (14.8) | 117 (16.8) | 79 (15.1) | 30 (13.2) | ||
| eGFR(mL/min/1.73 m2) | 53.3 ± 31.1 | 27.8 ± 19.0 | 45.5 ± 28.0 | 65.7 ± 30.0 | 72.3 ± 27.6 | <0.001 | <0.001 |
| Hemoglobin (g/dL) | 12.8 ± 2.0 | 11.2 ± 1.8 | 12.6 ± 2.0 | 13.4 ± 1.9 | 13.8 ± 1.8 | <0.001 | <0.001 |
| Uric acid (mg/dL) | 7.0 ± 1.9 | 7.6 ± 1.9 | 7.3 ± 2.0 | 6.6 ± 1.9 | 6.5 ± 1.7 | <0.001 | <0.001 |
| Albumin (g/dL) | 4.2 ± 0.4 | 4.0 ± 0.4 | 4.1 ± 0.5 | 4.3 ± 0.4 | 4.3 ± 0.4 | <0.001 | <0.001 |
| Total cholesterol (mg/dL) | 174.6 ± 38.8 | 164.5 ± 44.3 | 173.3 ± 38.7 | 177.9 ± 36.7 | 180.2 ± 36.7 | <0.001 | <0.001 |
| CRP, median, (Q1, Q3) (mg/L) | 0.6 (0.2, 1.6) | 0.7 (0.4, 2.1) | 0.6 (0.2, 1.7) | 0.5 (0.2, 1.4) | 0.5 (0.2, 1.4) | 0.001 | <0.001 |
| Phosphorus (mg/dL) | 3.7 ± 0.7 | 4.2 ± 0.9 | 3.7 ± 0.7 | 3.5 ± 0.6 | 3.6 ± 0.6 | <0.001 | <0.001 |
| *Corrected Ca (mg/dL) | 9.0 ± 0.4 | 8.8 ± 0.5 | 9.0 ± 0.4 | 9.1 ± 0.4 | 9.1 ± 0.4 | <0.001 | <0.001 |
| iPTH, median (Q1, Q3) (pg/mL) | 50.9 (33.7, 83.7) | 91.6 (53.3, 144.7) | 56.2 (36.9, 94.7) | 43.0 (30.2, 65.0) | 39.1 (27.7, 54.0) | <0.001 | <0.001 |
| UPCR (Q1, Q3) (g/g) | 0.49 (0.15, 1.48) | 1.08 (0.39, 2.25) | 0.58 (0.19, 1.83) | 0.34 (0.10, 0.93) | 0.27 (0.07, 0.81) | <0.001 | <0.001 |
| DPI (g/kg/day) | 0.95 ± 0.26 | 0.93 ± 0.28 | 0.92 ± 0.25 | 0.98 ± 0.28 | 0.96 ± 0.25 | 0.002 | 0.060 |
| Medications | |||||||
| ACEi or ARB, n (%) | 1418 (85.5) | 181 (86.2) | 589 (84.5) | 448 (85.5) | 200 (87.7) | 0.673 | 0.665 |
| Diuretics, n (%) | 498 (30.0) | 83 (39.5) | 220 (31.6) | 125 (23.9) | 70 (30.7) | <0.001 | 0.003 |
| †Phosphate binder, n (%) | 154 (9.3) | 31 (14.8) | 68 (9.8) | 37 (7.1) | 18 (7.9) | 0.010 | 0.005 |
*Corrected Ca (mg/dL) = measured total Ca (mg/dL) + 0.8 × [4 − measured serum albumin (g/dL)].
†Only calcium-based phosphate binders were prescribed to members of our patient cohort.
TCO2, total CO2; SD, standard deviation; BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; MAP, mean arterial pressure; DM, diabetes mellitus; HTN, hypertension; CV, cardiovascular; CAD, coronary artery disease; HF, heart failure; PVD, peripheral vascular disease; CKD, chronic kidney disease; DN, diabetic nephropathy; PKD, polycystic kidney disease; eGFR, estimated glomerular filtration rate as determined by the CKD-EPI creatinine equation; CRP, C-reactive protein; Ca, calcium; iPTH, intact parathyroid hormone; UPCR, urine protein creatinine ratio; DPI, dietary protein intake; ACEi, angiotensin converting enzyme inhibitor; ARB, angiotensin II receptor blocker.