Table 3.
Performance of Estimating Equations in the NECOSAD Cohort
| Variables | Guangzhou PD Study Equations |
Shafi et al10 Equations |
|||
|---|---|---|---|---|---|
| RMSEa | Biasb | Precisionc | Accuracy (95% CI)d | Accuracy (95% CI)d | |
| Equations to estimate mClUN(mL/min) | |||||
| mL/min (95% CI) | mL/min (95% CI) | ||||
| UN-creatinine | 0.694 (0.656 to 0.730) | 0.8 (0.7 to 0.9) | 2.1 (1.9 to 2.3) | 72% (69% to 75%) | 75% (72% to 78%)e |
| BTP | 0.630 (0.594 to 0.665) | 0.4 (0.3 to 0.5) | 1.8 (1.6 to 1.9) | 78% (75% to 80%)f | 81% (78% to 83%)e,g |
| B2M | 0.588 (0.549 to 0.622) | 0.7 (0.6 to 0.8) | 1.7 (1.5 to 1.8) | 80% (77% to 83%)f | 79% (76% to 81%)g |
| Cystatin C | 0.667 (0.626 to 0.702) | −0.3 (−0.4 to −0.2) | 2.0 (1.8 to 2.2) | 75% (72% to 78%) | 79% (76% to 82%)e,g |
| BTP-B2M | 0.514 (0.483 to 0.545) | 0.5 (0.4 to 0.6) | 1.5 (1.4 to 1.8) | 81% (78% to 84%)f | 81% (78% to 84%)g |
| Equations to estimate mClUN-cr(mL/min/1.73 m2) | |||||
| mL/min/1.73 m2 (95% CI) | mL/min/1.73 m2 (95% CI) | ||||
| UN-creatinine | 0.606 (0.569 to 0.642) | 0.7 (0.6 to 0.9) | 2.2 (2.0 to 2.4) | 68% (65% to 71%) | 68% (65% to 72%) |
| BTP | 0.550 (0.519 to 0.582) | 0.2 (0.1 to 0.4) | 2.1 (1.9 to 2.3) | 72% (69% to 75%)h | 71% (68% to 74%) |
| B2M | 0.513 (0.482 to 0.546) | 0.5 (0.4 to 0.6) | 1.8 (1.7 to 2.0) | 78% (75% to 80%)f | 69% (66% to 72%)i |
| Cystatin C | 0.572 (0.536 to 0.607) | −0.2 (−0.4 to −0.1) | 2.3 (2.1 to 2.5) | 71% (68% to 74%) | 72% (69% to 75%)g |
| BTP-B2M | 0.511 (0.478 to 0.543) | 0.2 (0.1 to 0.4) | 1.8 (1.6 to 2.0) | 79% (77% to 82%)f | 75% (72% to 78%)e,g |
Note: n = 826. All associations between filtration marker and outcome are linear except for B2M (2-slope polynomial model, breakpoint for B2M at 24 [mClUN] and 23 [mClUN-cr] mg/L). UN-creatinine equations also contain age and sex as covariables. Of note, equations developed by Shafi et al10 contained in part different covariables.
Abbreviations: B2M, β2-microglobulin; BTP, β-trace-protein; CI, confidence interval; RMSE, root-mean-square error; mClUN, measured clearance of urea nitrogen in mL/min; mClUN-cr, average measured clearance of urea nitrogen and creatinine in mL/min/1.73 m2; NECOSAD, Netherlands Cooperative Study on the Adequacy of Dialysis; PD, peritoneal dialysis; UN, urea nitrogen.
RMSE defined as the standard deviation of mean difference between (ln) measured and (ln) estimated clearance.
Bias defined as the median difference between measured and estimated clearance.
Precision defined as interquartile range of the differences between measured and estimated total clearance.
Accuracy defined as the percentage of estimates within ± 2 units of measured clearance.
Significance level of P < 0.05.
Significance level of P < 0.001 for the difference between the accuracy of the corresponding equation and the UN-creatinine equation.
Significance level of P < 0.05 for difference between the corresponding equation and the UN-creatinine equation published by Shafi et al.10
Significance level of P < 0.05.
Significance level of 0.01 for the difference between the accuracy of the corresponding equation and the similar Guangzhou PD Study equation (ie, same row).