Table 1.
Subject Characteristics by Dataset
| Development (n=5,504) |
Internal validation (n=2,750) |
External validation (n=3,896) |
P values* | |
|---|---|---|---|---|
| Mean age (SD), y | 47 (15) | 47 (15) | 50 (15) | p<0.001 |
| Age, n (%) | p<0.001 | |||
| <40 y | 2058 (37) | 1018 (37) | 1136 (29) | |
| 41-65 y | 2751 (50) | 1403 (51) | 2192 (56) | |
| >65 y | 695 (13) | 329 (12) | 568 (15) | |
| 66-70 y | 476 (9) | 220 (8) | 254 (7) | |
| 71-75 y | 150 (3) | 66 (2) | 185 (5) | |
| 76-80 y | 41 (0) | 30 (1) | 92 (2) | |
| >80 y | 28 (0) | 13 (0) | 37 (0) | |
| Women, n (%) | 2391 (43) | 1215 (44) | 1767 (45) | p=0.084 |
| Race, n (%) | p<0.001 | |||
| Black | 1728 (32) | 857 (31) | 384 (10) | |
| Hispanic | 247 (5) | 106 (4) | 67 (2) | |
| Asian | 62 (1) | 38 (1) | 67 (2) | |
| White and other | 3467 (63) | 1749 (64) | 3378 (87) | |
| Kidney donor, n (%) | 694 (13) | 336 (12) | 608 (16) | p<0.001 |
| Transplant recipient, n (%) | 241 (4) | 119 (4) | 1134 (29) | p<0.001 |
| Diabetes, n (%) | 1581 (29) | 825 (30) | 1089 (28) | p=0.173 |
| Mean height (SD), cm | 170 (10) | 170 (10) | 170 (10) † | p=0.90 |
| Mean weight (SD), kg | 82(20) | 82 (20) | 79 (18) | p<0.001 |
| Mean body mass index (SD), kg/m2 | 28 (6) | 28 (6) | 27 (6) † | p<0.001 |
| Mean body surface area (SD), m2 | 1.93 (0.20) | 1.93 (0.20) | 1.90 (0.23) † | p<0.001 |
| Mean GFR (SD), mL/min per 1.73 m2‡ | 68 (40) | 67 (40) | 68 (36) | p=0.70 |
| Mean serum creatinine level (SD) | p<0.001 | |||
| μmol/L | 146 (106) | 148 (106) | 134 (88) | |
| mg/dL | 1.65 (1.20) | 1.67 (1.20) | 1.52 (1.00) |
GFR = glomerular filtration rate.
*
For comparison of the combined development and internal validation data sets vs. the external validation data set.
†
The sample size is 3875 because of missing data.
‡
To convert GFR from mL/min per 1.73 m2 to mL/s per m2, multiply by 0.0167.