Table 4.
Performance of equations in the validation dataset
| Equations | R2 | Bias (95% CI) | IQR (95% CI) | RMSE (95% CI) | P30% (95% CI) | P15% (95% CI) | P7.5% (95% CI) |
|---|---|---|---|---|---|---|---|
| Combination | 0.90 | 3.5 (2.3–4.8) | 6.5 (4.8–9.6) | 6.2 (5.1–7.5) | 98.5 (91.4–100.0) | 89.7 (80.0–95.2) | 64.7 (52.8–75.0) |
| d-Serine clearance | 0.83 | 5.6 (3.5–7.2)* | 10.7 (7.1–14.8) | 8.2 (6.9–9.6) | 97.1 (89.3–99.8) | 79.4 (68.2–87.4)* | 45.6 (34.3–57.4)* |
| Creatinine clearance | 0.87 | 4.5 (3.2–5.7)* | 8.9 (6.5–12.8) | 7.3 (6.0–8.7) | 97.1 (89.3–99.8) | 83.8 (73.1–90.9)* | 51.5 (39.8–63.0)* |
| eGFR_cys | 0.65 | 7.2 (5.6–11.9)* | 16.6 (11.4–19.9) | 12.8 (10.6–15.4) | 88.2 (78.2–94.2)* | 58.8 (47.0–69.8)* | 36.8 (26.3–48.7)* |
| eGFR_cre | 0.55 | 6.9 (5.3–9.4)* | 14.1 (10.2–18.8) | 13.7 (10.4–17.3) | 85.3 (74.8–92.0)* | 64.7 (52.8–75.0)* | 33.8 (23.7–45.7)* |
The combination denotes an equation based on a combination of clearances of d-serine and creatinine. eGFR_cre and eGFR_cys denote creatinine- and cystatin C-based estimated glomerular filtration rates (eGFRs), respectively, based on the Japanese formula.2,18 Performances of conventionally-used eGFRs were shown as references. Bias, absolute value of residual. IQR, interquartile range of difference; RMSE, root mean square error. Accuracy was calculated as the ratios that differed from inulin clearance by less than 30%, 15%, and 7.5% (P30, P15, and P7.5). CI, confidence interval. *Statistically significant versus combination equation.