Table 1.
Characteristics of Study Participants, According to Data Set.*
| Characteristic | Development and Internal Validation (N = 5352) | External Validation (N = 1119) | P Value |
|---|---|---|---|
| Age — yr | 47±15 | 50±17 | <0.001 |
| Age group — no. (%) | |||
| <40 yr | 2008 (38) | 357 (32) | <0.001 |
| 40–65 yr | 2625 (49) | 530 (47) | |
| >65 yr | 719 (13) | 232 (21) | |
| Male sex — no. (%) | 3107 (58) | 663 (59) | 0.46 |
| Black race — no. (%)† | 2123 (40) | 30 (3) | <0.001 |
| Diabetes — no. (%) | 1726 (32) | 594 (53) | <0.001 |
| Body-mass index‡ | |||
| Mean | 28±6 | 25±4 | <0.001 |
| <20 — no. (%) | 214 (4) | 81 (7) | <0.001 |
| 20–24 — no. (%) | 1585 (30) | 503 (45) | |
| 25–30 — no. (%) | 1881 (35) | 386 (35) | |
| >30 — no. (%) | 1671 (31) | 149 (13) | |
| Mean weight — kg | 83±20 | 74±15 | <0.001 |
| Mean height — cm | 171±10 | 170±9 | 0.017 |
| Mean body-surface area — m2 | 1.94±0.24 | 1.85±0.21 | <0.001 |
| Mean serum cystatin C — ml/liter | 1.4±0.7 | 1.5±0.8 | 0.01 |
| Mean serum creatinine — mg/dl§ | 1.6±0.9 | 1.6±1.1 | 0.15 |
| Mean measured GFR — ml/min/1.73 m2 of body-surface area | 68±39 | 70±41 | 0.13 |
| Measured GFR — no. (%) | |||
| <15 ml/min/1.73 m2 | 160 (3) | 51 (5) | <0.001 |
| 15–29 ml/min/1.73 m2 | 785 (15) | 166 (15) | |
| 30–59 ml/min/1.73 m2 | 1765 (33) | 316 (28) | |
| 60–89 ml/min/1.73 m2 | 1105 (21) | 215 (19) | |
| 90–119 ml/min/1.73 m2 | 862 (16) | 199 (18) | |
| >120 ml/min/1.73 m2 | 675 (13) | 172 (15) | |
*
Plus–minus values are means±SD. GFR denotes glomerular filtration rate.
†
Race was determined by the investigators or by self-report, depending on the study.
‡
The body-mass index is the weight in kilograms divided by the square of the height in meters.
§
To convert the values for serum creatinine to micromoles per liter, multiply by 88.4.