Table 3.

Absolute and relative predictive error (mean ± SD) and agreement C-statistics measures of the GFR predictions against the reference GFR performed in the validation cohort by the different methods investigated^a

Variables	Absolute PE (ml/min)	Relative PE (%)	Absolute RMSE (ml/min)	Relative RMSE (%)	CCC	TDI	CP	P10	n
GFRClin2	–0.3 ± 3.8	–0.2 ± 7.1	2.4 ± 2.9	4.4 ± 5.6	0.994 (0.990)	11.4 (13.7)	84.5 (75.9)	91%	43
GFRModel5h,4s	–0.5 ± 1.9	–0.9 ± 4.5	1.4 ± 1.5	2.8 ± 3.6	0.997 (0.995)	7.3 (8.7)	97.2 (92.6)	98%	42
GFRModel3h,4s	–0.1 ± 6.9	–1.4 ± 18.0	4.8 ± 4.9b	11.0 ± 14.0b	0.951 (0.921)	35.5 (43.5)	386. (32.6)	65%b	43
GFRModel5h,3s	–2.0 ± 5.7	–2.0 ± 5.7	3.0 ± 5.3	5.2 ± 6.8	0.987 (0.981)	14.8 (18.1)	73.2 (63.4)	86%	42

CCC, concordance correlation coefficient; CP, coverage probability; GFR, glomerular filtration rate; PE, predictive error (predicted concentration – observed concentration); RMSE, root mean squared error $\left(\sqrt{P{E}^2}\right)$.

^aReference GFR was obtained by using all individual iohexol concentrations with the final population model as Bayesian prior. Predictions were done with limited sampling strategies according to the following: current clinical 2-point method (GFR_Clin2), final population model as Bayesian prior using 4-point, restricted to the first 5 hours (GFR_Mod5h,4s); using 4-point, restricted to the first 3 hours (GFR_Mod3h,4s); and using 3-point, restricted to the first 5 hours (GFR_Mod5h,3s). Values in parentheses are upper limits of 95% confidence intervals for TDI and lower limits of 95% confidence intervals for Accuracy, Precision, CCC, and CP. P10 is the proportion of GFR values obtained by the evaluated methods that are within 10% of GFR_ref. TDI allowance, 10; CP allowance, 0.9; α, 0.05.

^bP < 0.05 vs. clinical 2-point method.