Table 2.
Predictive accuracy of GFR and secretory solute clearances for predicting kidney furosemide clearance
| Predictor | MAE between Predicted and Measured Drug Clearance, ml/min | Difference in MAE Comparing iGFR with Secretory Clearance, ml/min (95% CI)a | MPE between Predicted and Measured Drug Clearance, % | Difference in MPE Comparing iGFR with Secretory Clearance, % (95% CI)a |
|---|---|---|---|---|
| iGFR | 21.5 | — | 30.0 | — |
| eGFRcreatinine | 22.4 | −0.9 (−5.6 to 3.5) | 33.5 | −3.5 (−12.9 to 3.7) |
| Secretion score | 17.2 | 4.3 (−1.1 to 9.1) | 24.1 | 5.9 (−2.1 to 14.0) |
| Individual clearance | ||||
| Pyridoxic acid | 18.9 | 2.6 (−2.9 to 7.0) | 27.3 | 2.7 (−6.8 to 10.1) |
| Isovalerylglycine | 25.7 | −4.2 (−11.4 to 2.2) | 42.5 | −12.5 (−26.9 to 1.1) |
| Tiglylglycine | 27.0 | −5.5 (−12.9 to 1.1) | 43.8 | −13.8 (−32.2 to 1.9) |
| Kynurenic acid | 21.0 | 0.5 (−6.2 to 6.3) | 33.3 | −3.3 (−16.8 to 9.2) |
| Xanthosine | 28.3 | −6.8 (−14.3 to 0.1) | 48.0 | −18.0 (−35.9 to −1.3) |
| Cinnamoylglycine | 20.9 | 0.6 (−5.1 to 5.3) | 29.2 | 0.8 (−8.2 to 9.7) |
| Indoxyl sulfate | 20.6 | 0.9 (−4.0 to 5.6) | 31.1 | −1.1 (−10.4 to 9.0) |
| p-cresol sulfate | 20.0 | 1.5 (−3.3 to 5.7) | 29.5 | 0.5 (−5.9 to 8.5) |
iGFR was measured by iohexol disappearance. eGFR was on the basis of serum creatinine concentrations from the 2009 Chronic Kidney Disease Epidemiology Collaboration equation. MAE, mean absolute error; MPE, mean proportionate error.
a
The 95% CIs were derived using leave-one-out cross validation with bootstrap with 500 iterations. Positive values indicate greater agreement for secretory solute clearances, and negative values indicate greater agreement for iGFR. None of the differences remained significant after correction for multiple comparisons using the Hommel method.