Article Figures & Data
Figures
- Figure 1.
Flow chart showing how patients were selected for this analysis from the electronic-health-record-based registry. CKD, chronic kidney disease; eGFR, estimated GFR.
- Figure 2.
Kaplan–Meier survival curve based on serum bicarbonate levels among chronic kidney disease patients.
- Figure 3.
Associations (log hazard and 95% confidence interval) between all-cause mortality and baseline serum bicarbonate levels. Model adjusted for age, gender, African-American race, body mass index, diabetes, hypertension, hyperlipidemia, malignancy, congestive heart failure, cerebrovascular disease, and coronary artery disease at chronic kidney disease diagnosis and estimated GFR, use of renin-angiotensin system blockers and diuretics, hemoglobin and albumin.
- Figure 4.
Hazard ratio and 95% confidence interval (CI) of all-cause mortality associated with low serum bicarbonate levels among select subgroups. eGFR, estimated GFR.
Tables
Variablea Not 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 [%]) 63.8 48.1 69.7 63.7 Stage 3b (GFR 30 to 44 [%]) 28.0 32.4 24.2 26.5 Stage 4 (GFR 15 to 29 [%]) 8.2 19.5 6.1 9.8 Male gender (%) 52.6 49.6 45.5 43.3 African American (%) 8.9 18.5 12.2 16.1 Diabetes (%) 12.9 27.7 22.6 21.6 Hypertension (%) 79.3 87.6 89.7 84.8 Coronary artery disease (%) 14.8 20.9 23.2 26.1 Cerebrovascular disease (%) 7.8 9.3 9.5 8.6 Congestive heart failure (%) 2.5 9.1 8.6 21.9 Malignancy (%) 29.2 26.1 23.6 23.2 Hyperlipidemia (%) 72.9 71.7 79.5 75.2 COPD (%) 6.3 7.8 9.0 20.1 Smoking (%) nonsmoker 84.0 83.5 88.7 86.5 smoker 9.0 10.2 7.0 7.7 missing information 7.0 6.3 4.3 5.8 BMI kg/m2 (%) <18.5 0.96 1.8 1.1 1.2 18.5 to 24.9 23.8 24.3 23.1 28.1 25 to 29.9 34.5 32.8 35.6 28.5 30 to 34.9 19.7 20.3 21.1 15.6 35 to 39.9 9.1 9.4 8.8 12.1 > 40 4.7 6.9 5.8 9.2 missing information 7.4 4.5 4.3 5.2 Albumin (g/dl)b (mean [SD]) 4.0 ± 0.51 4.0 ± 0.53 4.2 ± 0.41 4.1 ± 0.48 Hemoglobin (g/dl) (mean [SD]) 12.9 ± 1.8 12.1 ± 2.0 13.0 ± 1.7 12.8 ± 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.
- Table 2.
Factors associated with low serum bicarbonate and high serum bicarbonate at CKD diagnosis
Effect Model 1 (n = 37,346) Model 2 (n = 32,623) Low Bicarbonate (<23 mmol/L) OR (95% CI) P High Bicarbonate (>32 mmol/L) OR (95% CI) P Age quintiles <0.01 0.09 62.4 to 70.1 versus 18 to 62.4 0.72 (0.66, 0.79) 0.79 (0.61, 1.02) 70.2 to 76.4 2 versus 18 to 62.4 0.63 (0.58, 0.70) 0.71 (0.55, 0.93) 76.4 to 82.3 versus 18 to 62.4 0.57 (0.52, 0.63) 0.82 (0.63, 1.06) 82.3 to 104 versus 18 to 62.4 0.50 (0.45, 0.55) 0.73 (0.56, 0.96) Male gender 1.32 (1.23, 1.40) <0.01 0.94 (0.79, 1.11) 0.46 African-American race versus others 1.24 (1.14, 1.35) <0.01 1.09 (0.86, 1.37) 0.49 BMI group (kg/m2) 0.17 <0.01 <18.5 versus 18.5 to 24.9 1.28 (1.00, 1.63) 0.82 (0.40, 1.68) 25 to 29.9 versus 18.5 to 24.9 0.96 (0.89, 1.04) 0.71 (0.57, 0.88) 30 to 34.9 versus 18.5 to 24.9 0.96 (0.87, 1.05) 0.67 (0.51, 0.86) 35 to 39.9 versus 18.5 to 24.9 0.94 (0.84, 1.07) 1.17 (0.88, 1.56) 40+ versus 18.5 to 24.9 0.88 (0.77, 1.02) 1.16 (0.83, 1.62) missing versus 18.5 to 24.9 1.03 (0.87, 1.21) 0.97 (0.65, 1.46) eGFR (per 10-ml/min per 1.73 m2 increase) 0.66 (0.64, 0.67) <0.01 0.92 (0.85, 0.998) 0.046 Diabetes 1.20 (1.11, 1.29) <0.01 0.79 (0.64, 0.98) 0.03 Hypertension 1.03 (0.93, 1.14) 0.54 0.71 (0.56, 0.90) 0.04 Hyperlipidemia 0.79 (0.73, 0.85) <0.01 0.84 (0.69, 1.03) 0.10 Coronary artery disease 0.94 (0.87, 1.02) 0.12 1.13 (0.92, 1.38) 0.25 Congestive heart failure 0.82 (0.73, 0.91) <0.01 2.57 (2.08, 3.16) <0.01 COPD 0.88 (0.78, 0.98) 0.019 2.52 (2.05, 3.09) <0.01 Smoking <0.01 0.77 yes versus no 1.38 (1.24, 1.54) 0.92 (0.67, 1.27) missing versus no 1.28 (1.12, 1.47) 1.10 (0.75, 1.60) Hb per 1 g/dl increase 0.83 (0.82, 0.85) <0.01 1.01 (0.96, 1.06) 0.83 Albumin per 1 mg/dl increase 0.79 (0.74, 0.84) <0.01 0.71 (0.59, 0.86) <0.01 Model was additionally adjusted for the year of inclusion in the registry. CKD, chronic kidney disease; OR, odds ratio; CI, confidence interval; BMI, body mass index; eGFR, estimated glomerular filtration rate; COPD, chronic obstructive pulmonary disease.
- Table 3.
Associations between serum bicarbonate levels and all-cause mortality among chronic kidney disease patients
Bicarbonate Group Unadjusted HR [95% CI] (n = 41,445) Model A HR [95 %CI] (n = 41,445) Model B HR [95 %CI] (n = 37,687) Model C HR [95% CI] (n = 37,687) <23 mmol/L versus 23 to 32 mmol/L 1.65 (1.56, 1.75) 1.75 (1.65, 1.85) 1.35 (1.27, 1.44) 1.23 (1.16, 1.31) >32 mmol/L versus 23 to 32 mmol/L 2.12 (1.86, 2.42) 2.08 (1.83, 2.37) 1.76 (1.54, 2.02) 1.74 (1.52, 2.00) Model A adjusted for age, gender, and race. Model B adjusted variables included in Model A, plus body mass index, diabetes, hypertension, hyperlipidemia, malignancy, congestive heart failure, cerebrovascular disease, coronary artery disease, chronic obstructive pulmonary disease, history of angiotensin-converting enzyme/angiotensin receptor blocker prescription, history of diuretic prescription at chronic kidney disease diagnosis, and hemoglobin and albumin. Model C adjusted variables included in Model B, plus baseline estimated GFR. HR, hazard ratio; CI, confidence interval.
Serum bicarbonate and mortality in stage 3 and stage 4 chronic kidney disease
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