TABLE 2.
Biochemical measures of kidney function
| Black adults | White adults | P value | Effect size | |||||
|---|---|---|---|---|---|---|---|---|
| Plasma Na+ (mEq/L) | 140.5 | ± | 1.7 | 140.1 | ± | 1.7 | 0.440 | 0.223 |
| Plasma K+ (mEq/L) | 3.6 | (0.4) | 3.7 | (0.5) | 0.634 | 0.079 | ||
| Plasma Cl- (mEq/L) | 101.1 | ± | 2.2 | 99.8 | ± | 2.0 | 0.031 | 0.628 |
| Plasma Osm (mOsm/kgH2O) | 281 | ± | 5 | 282 | ± | 5 | 0.558 | 0.169 |
| Blood urea nitrogen (mg/dL) | 18.6 | (4.1) | 18.9 | (3.5) | 0.594 | 0.089 | ||
| Serum creatinine (mg/dL) | 0.91 | ± | 0.29 | 0.86 | ± | 0.14 | 0.455 | 0.214 |
| Estimated GFR (mL/min/1.73m2) | 152 | (24) | 150 | (18) | 0.663 | 0.075 | ||
| Hemoglobin (g/dL) | 13.5 | ± | 1.6 | 14.4 | ± | 1.8 | 0.073 | 0.517 |
| Hematocrit (%) | 42.6 | ± | 4.6 | 44.0 | ± | 4.0 | 0.261 | 0.322 |
| Urine volume (mL) | 1501 | ± | 978 | 2526 | ± | 1310 | 0.004 | 0.463 |
| Collection time (min) | 1448 | ± | 143 | 1489 | ± | 90 | 0.210 | 0.361 |
| Urine urea (mg/dL) | 1455 | (825) | 1212 | (805) | 0.139 | 0.241 | ||
| Urine creatinine excretion (mg/min) | 1.17 | (0.49) | 1.20 | (0.61) | 0.701 | 0.064 | ||
| Creatinine clearance (mL/min/1.73m2) | 130 | ± | 34 | 116 | ± | 28 | 0.135 | 0.463 |
Data are presented as mean ± SD for normally distributed data (Shapiro-Wilk > 0.05) or median (interquartile range) for nonparametric data (Shapiro-Wilk < 0.05). When Shapiro-Wilk was > 0.05 we used independent samples t-test for difference testing and Cohen’s d for effect size. When Shapiro-Wilk was < 0.05 we used Mann-Whitney U test for difference testing and Rank biserial correlation for effect size.
Samples sizes for blood and urine measures was n = 21–23 for Black adults and 28–30 for White adults. Because creatinine clearance includes both urine and blood samples the sample size was n = 19 for Black adults and n = 27 for White adults.
Abbreviations: Na+, sodium; K+, potassium; Cl-, chloride; Osm, osmolality; GFR, glomerular filtration rate.