Table 1.
Demographic, serum, and urinary parameters of all subjects, and comparison between calcium stone formers and uric acid stone formers. Continuous variables are summarized as mean ± standard deviation or median [25th, 75th percentile].
| Total Sample | Calcium Stone Formers (CaSF) |
Uric Acid Stone Formers (UASF) |
P-value (UASF vs. CaSF) |
|
|---|---|---|---|---|
| Demographics | ||||
| Sample Size (n) | 1516 | 1365 | 151 | |
| Proportion in Total Population (%) | 90% | 10% | ||
| Age (years) | 43.7±12.6 | 43.1±12.6 | 49.6±11.7 | <0.0001 |
| Race/Ethnicity | 0.69 | |||
| White | 1414 | 1271 | 143 | |
| Black | 45 | 41 | 4 | |
| Hispanic | 16 | 15 | 1 | |
| Asian | 29 | 28 | 1 | |
| American Indians | 5 | 5 | 0 | |
| Weight (kg) | 81.5±20.0 | 80.3±19.5 | 92.8±20.8 | <0.0001 |
| BMI (kg/m2) | 27.4±6.0 | 27.0±5.8 | 30.7±6.7 | <0.0001 |
| % Female | 33% | 34% | 25% | 0.03 |
| Serum | ||||
| Calcium (mmol/L) | 2.37±0.11 | 2.37±0.11 | 2.37±0.11 | 0.46 |
| Uric Acid(µmol/L) | 352±96 | 348±93 | 394±110 | <0.0001 |
| Glucose (mmol/L) | 5.2±1.2 | 5.1±1.1 | 5.9±1.8 | <0.0001 |
| Triglyceride (mmol/L) | 1.7±1.4 | 1.7±1.4 | 2.1±1.7 | 0.01 |
| Urine | ||||
| Volume (mL/day) | 1808±927 | 1809±936 | 1801±849 | 0.94 |
| pH | 5.99±0.45 | 6.03±0.44 | 5.65±0.44 | <0.0001 |
| Cr-Clearance (mL/min/1.73m2) | 97.5±27.9 | 97.6±27.4 | 95.8±31.6 | 0.57 |
| Creatinine (mmol/day) | 14.0±4.5 | 13.8±4.4 | 15.6±4.4 | <0.0001 |
| Sodium (mEq/day) | 175±82 | 173±82 | 189±84 | 0.02 |
| Potassium (mEq/day) | 52±22 | 51±22 | 56±23 | 0.01 |
| Calcium (mmol/day) | 6.1±3.1 | 6.2±3.1 | 5.7±3.4 | 0.13 |
| Oxalate (mmol/day) | 0.4±0.2 | 0.4±0.2 | 0.4±0.2 | 0.29 |
| Uric Acid (mmol/day) | 3.5±1.3 | 3.5±1.3 | 3.3±1.4 | 0.08 |
| Citrate (mmol/day) | 2.68±1.62 | 2.66±1.57 | 2.82±2.03 | 0.40 |
| Phosphorus (mmol/day) | 31±12 | 30±11 | 34±12 | 0.001 |
| Sulfate (mEq/day) | 39.8±19.3 | 38.7±17.7 | 46.9±22.4 | <0.0001 |
| Ammonium (mEq/day) | 36.8±17.2 | 36.2±17.2 | 39.9±17.0 | 0.05 |
| NAE (mEq/day) | 48.2±29.3 | 46.2±29.4 | 59.3±25.7 | <0.0001 |
| NAE/Sulfate (mEq/mEq) | 1.19 [0.88, 1.61] | 1.18 [0.87, 1.61] | 1.26 [0.96, 1.59] | 0.30 |
| Ammonium/NAE (mEq/mEq) | 0.75 [0.64, 0.91] | 0.77 [0.66, 0.92] | 0.65 [0.59, 0.77] | <0.0001 |
| Ammonium/Sulfate (mEq/mEq) | 0.90 [0.68, 1.21] | 0.91 [0.69, 1.21] | 0.79 [0.61, 1.11] | 0.01 |
| NGIA (mEq/day) | 28.5±42.6 | 30.0±42.0 | 18.0±45.1 | 0.01 |
| NGIA/Potassium (mEq/mEq) | 0.54 [0.28, 0.81] | 0.56 [0.29, 0.83] | 0.40 [0.11, 0.64] | 0.0004 |
| Urine per Kg Bodyweight | ||||
| Creatinine (µmol/day/kg) | 173.2±45.5 | 173.4±45.5 | 171.3±45.3 | 0.59 |
| Sodium (mEq/day/kg) | 2.17±0.94 | 2.18±0.95 | 2.07±0.88 | 0.14 |
| Potassium (mEq/day/kg) | 0.65±0.27 | 0.65±0.28 | 0.62±0.25 | 0.14 |
| Calcium (mmol/day/kg) | 0.08±0.04 | 0.08±0.04 | 0.06±0.04 | <0.0001 |
| Oxalate (µmol/day/kg) | 4.8±2.4 | 4.9±2.4 | 4.4±1.7 | 0.004 |
| Uric Acid (µmol/day/kg) | 43.6±15.6 | 44.4±15.3 | 36.5±16.1 | <0.0001 |
| Citrate (µmol/day/kg) | 33.2±20.2 | 33.6±20.1 | 29.9±21.2 | 0.01 |
| Phosphorus (mmol/day/kg) | 0.38±0.13 | 0.38±0.13 | 0.37±0.12 | 0.24 |
| Sulfate (mEq/day/kg) | 0.48±0.21 | 0.48±0.20 | 0.50±0.22 | 0.34 |
| Ammonium (mEq/day/kg) | 0.44±0.22 | 0.44±0.22 | 0.43±0.21 | 0.70 |
| NAE (mEq/day/kg) | 0.56±0.36 | 0.55±0.37 | 0.63±0.30 | 0.02 |
| NGIA (mEq/day/kg) | 0.35±0.48 | 0.38±0.48 | 0.19±0.49 | <0.0001 |
Cr: Creatinine; NAE: Net Acid Excretion; NGIA: Net Gastrointestinal Absorption of Alkali; BW: Body Weight.