Table 1.

Characteristics of patients serum bicarbonate levels measured at CKD diagnosis

VariableaNot Measured (n = 2400)Low Bicarbonate (<23 mmol/L) (n = 5796)Normal Bicarbonate (23–32 mmol/L) (n = 35,301)High Bicarbonate (>32 mmol/L) (n = 652)
Ageb (mean [SD])73.7 (9.8)68.9 (13.8)72.3 (11.5)71.9 (12.2)
eGFRb (mean [SD])47.0 (10.0)42.3 (12.2)48.3 (9.7)46.4 (10.9)
eGFR stage
    Stage 3a (GFR 45 to 59 [%])63.848.169.763.7
    Stage 3b (GFR 30 to 44 [%])28.032.424.226.5
    Stage 4 (GFR 15 to 29 [%])8.219.56.19.8
Male gender (%)52.649.645.543.3
African American (%)8.918.512.216.1
Diabetes (%)12.927.722.621.6
Hypertension (%)79.387.689.784.8
Coronary artery disease (%)14.820.923.226.1
Cerebrovascular disease (%)7.89.39.58.6
Congestive heart failure (%)2.59.18.621.9
Malignancy (%)29.226.123.623.2
Hyperlipidemia (%)72.971.779.575.2
COPD (%)6.37.89.020.1
Smoking (%)
    nonsmoker84.083.588.786.5
    smoker9.010.27.07.7
    missing information7.06.34.35.8
BMI kg/m2 (%)
    <18.50.961.81.11.2
    18.5 to 24.923.824.323.128.1
    25 to 29.934.532.835.628.5
    30 to 34.919.720.321.115.6
    35 to 39.99.19.48.812.1
    > 404.76.95.89.2
    missing information7.44.54.35.2
Albumin (g/dl)b (mean [SD])4.0 ± 0.514.0 ± 0.534.2 ± 0.414.1 ± 0.48
Hemoglobin (g/dl) (mean [SD])12.9 ± 1.812.1 ± 2.013.0 ± 1.712.8 ± 1.9
  • Overall serum bicarbonate groups <23, 23 to 32, and >32 significantly different with P < 0.001 for all variables except cerebrovascular disease. The chi-squared test was used to assess categorical variables and ANOVA used for continuous variables. CKD, chronic kidney disease; eGFR, estimated GFR; COPD, chronic obstructive pulmonary disease; BMI, body mass index.

  • a Chi-squared test, P < 0.05, unless otherwise noted, comparing patients with serum bicarbonate measured versus all those not measured.

  • b t-test, P < 0.05, comparing patients with serum bicarbonate measured versus all those not measured.