Table 1.
Clinical Characteristics of the Patients in the Residual Kidney Function Study and the Netherlands Cooperative Study on Adequacy of Dialysis
| Development Cohort | Validation Cohort | ||||||
|---|---|---|---|---|---|---|---|
| RKF Study, Baltimore, Maryland, USA | NECOSAD, Netherlands | ||||||
| All Participants | Hemodialysis | Peritoneal Dialysis | |||||
| Characteristics | Mean (SD) or N (%) | Mean (SD) or N (%) | P (vs. RKF Study) | Mean (SD) or N (%) | P (vs. RKF Study) | Mean (SD) or N (%) | P (vs. RKF Study) |
| Number | 44 | 826 | 587 | 239 | |||
| Demographics | |||||||
| Age, years | 55.43 (11.29) | 60.22 (14.45) | 0.03 | 63.44 (13.33) | <0.001 | 52.28 (14.03) | 0.16 |
| Male, % | 28 (64%) | 496 (60%) | 0.75 | 334 (57%) | 0.43 | 162 (67.78%) | 0.60 |
| White, % | 9 (21%) | 724 (88%) | <0.001 | 539 (91%) | <0.001 | 185 (77.41%) | <0.001 |
| Clinical Characteristics | |||||||
| Cause of ESRD, % | 0.10 | 0.08 | 0.04 | ||||
| Diabetes | 12 (27%) | 128 (16%) | 96 (16%) | 32 (13%) | |||
| Glomerulonephritis | 6 (14%) | 118 (14%) | 60 (10%) | 58 (24%) | |||
| Other | 26 (59%) | 580 (70%) | 431 (73%) | 149 (62%) | |||
| Diabetes, % | 23 (52%) | 174 (21%) | <0.001 | 137 (24%) | <0.001 | 37 (16%) | <0.001 |
| Hemodialysis, % | 40 (91%) | 587 (71%) | 0.003 | 587 (100%) | <0.001 | 0 (0%) | <0.001 |
| Duration of Prior Dialysis, months | 26.7 (29.0) | 6.73 (4.49) | <0.001 | 5.42 (3.96) | <0.001 | 9.96 (4.07) | <0.001 |
| Height, cm | 171.6 (10.1) | 171.3 (9.9) | 0.83 | 170.4 (9.8) | 0.42 | 173.6 (9.8) | 0.23 |
| Weight, kg | 93.00 (27.46) | 73.81 (14.21) | <0.001 | 72.50 (14.02) | <0.001 | 77.04 (14.20) | <0.001 |
| Body Mass Index, Kg/m2 | 31.27 (7.76) | 25.10 (4.14) | <0.001 | 24.92 (4.17) | <0.001 | 25.54 (4.05) | <0.001 |
| Body Surface Area, m2 | 2.04 (0.31) | 1.86 (0.20) | <0.001 | 1.83 (0.20) | <0.001 | 1.91 (0.20) | <0.001 |
| Urea Volume of Distribution, L | 44.9 (11.6) | 38.0 (6.7) | <0.001 | 37.1 (6.4) | <0.001 | 40.1 (7.0) | <0.001 |
| 24-Hour Urine Volume, mL [Median (25th, 75th Percentiles)] | 799 (319, 1154) | 720 (389, 1217) | 0.33 | 679.71 (350, 1097) | 0.75 | 889 (472, 1522) | 0.02 |
| Urine Volume ≥250 mL, % | 34 (77%) | 718 (87%) | 0.07 | 501 (85%) | 0.19 | 217 (91%) | 0.02 |
| Measured Urinary Clearances, Median (25th, 75th Percentiles) | |||||||
| Urea Clearance, mL/min | 2.59 (0.92, 4.07) | 2.43 (1.31, 3.94) | 0.84 | 2.37 (1.28, 3.81) | 0.92 | 2.59 (1.41, 4.48) | 0.40 |
| Urea Clearance, mL/min/1.73 m2 | 2.42 (0.70, 3.31) | 2.30 (1.23, 3.66) | 0.24 | 2.24 (1.21, 3.57) | 0.33 | 2.36 (1.30, 3.97) | 0.13 |
| Creatinine Clearance, mL/min | 4.32 (1.62, 7.12) | 4.24 (2.33, 6.97) | 0.48 | 4.14 (2.21, 6.87) | 0.37 | 4.51 (2.73, 7.57) | 0.83 |
| Creatinine Clearance, mL/min/1.73 m2 | 3.71 (1.35, 5.96) | 4.03 (2.19, 6.57) | 0.61 | 3.98 (2.11, 6.52) | 0.68 | 4.05 (2.39, 7.09) | 0.48 |
| Average of Urea and Creatinine Clearance, mL/min | 3.58 (1.36, 5.50) | 3.42 (1.91, 5.42) | 0.67 | 3.38 (1.77, 5.19) | 0.51 | 3.55 (2.13, 6.11) | 0.88 |
| Average of Urea and Creatinine Clearance, mL/min/1.73 m2 | 3.09 (1.05, 4.82) | 3.17 (1.77, 5.13) | 0.45 | 3.14 (1.71, 4.95) | 0.54 | 3.24 (1.95, 5.62) | 0.30 |
| Weekly renal standard Kt/VUREA | 0.58 (0.16, 0.90) | 0.65 (0.36, 1.06) | 0.11 | 0.65 (0.35, 1.04) | 0.13 | 0.65 (0.37, 1.12) | 0.08 |
| Weekly renal standard Kt/VCREAT | 1.01 (0.33, 1.73) | 1.15 (0.62, 1.92) | 0.27 | 1.15 (0.60, 1.90) | 0.29 | 1.15 (0.67, 1.94) | 0.282 |
| Weekly renal standard Kt/VUREA, CREAT | 0.83 (0.25, 1.47) | 0.90 (0.50, 1.50) | 0.19 | 0.90 (0.49, 1.48) | 0.21 | 0.88 (0.53, 1.56) | 0.18 |
| Endogenous Serum Filtration Markers | |||||||
| Urea Nitrogen, mg/dL | 52.50 (15.74) | 64.92 (17.09) | <0.001 | 66.91 (16.67) | <0.001 | 60.05 (17.17) | 0.007 |
| Creatinine, mg/dL | 8.57 (3.07) | 8.73 (2.77) | 0.70 | 8.53 (2.63) | 0.93 | 9.22 (3.03) | 0.19 |
| β-Trace Protein, mg/L | 7.36 (3.13) | 6.93 (2.58) | 0.28 | 6.77 (2.45) | 0.13 | 7.32 (2.86) | 0.93 |
| β2 Microglobulin, mg/L | 24.28 (9.50) | 25.5 (9.49) | 0.42 | 25.55 (9.56) | 0.40 | 25.23 (9.34) | 0.53 |
| Cystatin C, mg/L | 5.24 (1.26) | 5.07 (1.10) | 0.35 | 5.02 (1.07) | 0.20 | 5.21 (1.17) | 0.91 |
Abbreviations: RKF, Residual Kidney Function; NECOSAD, The Netherlands Cooperative Study on the Adequacy of Dialysis; SD, Standard Deviation; ESRD, End Stage Renal Disease; Kt/V, Weekly clearance (Kt) divided by volume of total body water (V).
Conversion factors for units: creatinine in mg/dL to μmol/L, X 88.4; urea nitrogen in mg/dL to mmol/L, X 0.357.