Table 14.
Intraday and interday correlation and variance of urinary creatinine of the same sample according to the mean urinary creatinine level
| Mean of 2 urinary creatinine | Regression line | r | p | Bias of uCr | |||
|---|---|---|---|---|---|---|---|
| Range (mg/dl) | n | (mg/dl) | (mg/dl) | ||||
| Intraday | |||||||
| 3–4 h | |||||||
| LC1-2 | < 50.0 | 30 | 35.8 (29.1–43.6) | 2uCr = 1.001 × 1uCr-0.06834 | 0.99 | < 0.0001 | − 0.1− 0.2 to 0.1) |
| Mcl-2 | 50.0 to < 90.0 | 30 | 64.7(58.4-76.5)a2 | 2uCr = 0.9962 × 1uCr-0.2676 | 0.99 | < 0.0001 | − 0.1− 0.4 to 0.4) |
| HC1-2 | ≥ 90.0 | 28 | 128.1 (113.9–157.2)a2b2 | 2uCr = 1.013 × 1uCr-1.091 | 0.99 | < 0.0001 | 0.5 (− 0.6 to 1.3) |
| 3 min | |||||||
| LC3-4 | < 50.0 | 30 | 35.9 (28.7–43.7) | 4uCr = 1.008 × 3uCr + 0.07271 | 0.99 | < 0.0001 | 0.1 (− 0.1 to 0.4) |
| MC3-4 | 50.0 to < 90.0 | 29 | 64.4 (58.6–76.6)a2 | 4uCr = 0.9911 × 3uCr + 0.6046 | 0.99 | < 0.0001 | − 0.1(− 0.3 to 0.3) |
| HC3-4 | ≥ 90.0 | 29 | 126.9 (114.5–156.0)a2b2 | 4uCr = 0.9940 × 3uCr + 1.619 | 0.99 | < 0.0001 | 0.5 (− 0.4 to 0.9) |
| Interday | |||||||
| 3–4 days | |||||||
| LC1-3 | < 50.0 | 30 | 35.3 (28.7–43.8) | 3uCr = 0.9880 × 1uCr + 0.04098 | 0.99 | < 0.0001 | − 0.1 (− 0.2 to 0.1) |
| MC1-3 | 50.0 to < 90.0 | 29 | 64.5 (58.5–76.7)a2 | 3uCr = 1.023 × 1uCr-1.095 | 0.99 | < 0.0001 | 0.3 (− 0.1− 0.6)a1 |
| HC1-3 | ≥ 90.0 | 29 | 127.6 (113.6–154.1)a2b2 | 3uCr = 1.030 × 1uCr-3.276 | 0.99 | < 0.0001 | 1.1 (− 0.5 to 2.3) |
| LC1-4 | < 50.0 | 30 | 36.0 (29.0–43.8) | 4uCr = 1.004 × 1uCr-0.1729 | 0.99 | < 0.0001 | 0 (− 0.2 to 0.4) |
| MC1-4 | 50.0 to < 90.0 | 30 | 64.8 (58.6–76.7)a2 | 4uCr = 1.014 × 1uCr-0.4915 | 0.99 | < 0.0001 | 0.3 (− 0.2 to 1.0) |
| HC1-4 | ≥ 90.0 | 28 | 128.0 (114.2–157.6)a2b2 | 4uCr = 1.023 × 1uCr-1.646 | 0.99 | < 0.0001 | 1.1 (− 0.1 to 2.4) |
| 3–4 days | |||||||
| LC2-3 | < 50.0 | 30 | 35.3 (28.8–43.6) | 3uCr = 0.9859 × 2uCr + 0.1434 | 0.99 | < 0.0001 | 0 (− 0.4 to 0.3) |
| MC2-3 | 50.0 to < 90.0 | 29 | 64.6 (58.3–76.4)a2 | 3uCr = 1.022 × 2uCr − 1.109 | 0.99 | < 0.0001 | 0.5(0–0.7)a2 |
| HC2-3 | ≥ 90.0 | 29 | 127.7 (114.0–154.6)a2b2 | 3uCr = 1.016 × 2uCr − 2.048 | 0.99 | < 0.0001 | 0.6 (− 0.5 to 1.4) |
| LC2-4 | < 50.0 | 30 | 35.9 (29.1–43.5) | 4uCr = 1.002 × 2uCr − 0.09247 | 0.99 | < 0.0001 | 0.1 (− 0.1 to 0.3) |
| MC2-4 | 50.0 to < 90.0 | 30 | 64.9 (58.5–76.5)a2 | 4uCr = 1.017 × 2uCr − 0.7118 | 0.99 | < 0.0001 | 0.5 (0.2–0.8)a2 |
| HC2-4 | ≥ 90.0 | 28 | 127.8 (115.0–158.3)a2b2 | 4uCr = 1.010 × 2uCr − 0.5403 | 0.99 | < 0.0001 | 0.8 (− 0.3 to 1.7) |
The numbers of 1, 2, 3, and 4 represent the first, second, third, and fourth measurements, respectively, of urinary creatinine. Data are presented as median (IQR)
uCr urinary creatinine, LC low level of urinary creatinine; MC medium level of urinary creatinine; HC high level of urinary creatinine
a1p < 0.05 vs. LP
a2p < 0.01 vs. LP
b1p < 0.05 vs. MP
b2p < 0.01 vs. MP by the Steel–Dwass test; bias, difference of the later measurement against the previous measurement