Table 2.

Agreement between measured and estimated serum creatinine in community children

	Measured	Estimated
		bSCr back-calculated from GFR			bSCr estimated directly
	SCr	bSCrGFRSchwartz120 (reference)	bSCrGFRPottel120	bSCrGFRSchwartz137	bSCrupperlimit	bSCrheightCC	bSCrageCC
Mean (SD) (mg/dL)	0.29 (0.08)	0.31 (0.05)	0.29 (0.05)	0.28 (0.04)	0.40 (0.06)	0.29 (0.04)	0.29 (0.04)
Median (IQR) (mg/dL)	0.28 (0.23, 0.33)	0.31 (0.28, 0.34)	0.28 (0.26, 0.30)	0.27 (0.25, 0.30)	0.39 (0.35, 0.42)	0.28 (0.26, 0.31)	0.28 (0.26, 0.30)
Wilcoxona	–	***	NS	NS	***	NS	NS
Min, max (mg/dL)	0.19, 0.56	0.23, 0.34	0.22, 0.48	0.20, 0.44	0.35, 0.71	0.22, 0.44	0.23, 0.46
Correlation, SCr (r)	–	0.495	0.485	0.495	0.407	0.495	0.485
Bias (mg/dL)	–	0.025***	−0.002 (NS)	−0.014***	0.11***	−0.002 (NS)	−0.002 (NS)
Precision (mg/dL)	–	0.07	0.07	0.07	0.08	0.07	0.07
Accuracy
P10, %	–	24%	35%	33%	8%	29%	35%
P30, %	–	71%	79%	82%	33%	80%	78%
Proportional Bias	–	−0.66 ± 0.06 ***	− 0.70 ± 0.06***	−0.81 ± 0.06***	−0.35 ± 0.07***	−0.91 ± 0.06***	−0.88 ± 0.06***

Standard deviation (SD), IQR: Inter-quartile range, r: Spearman’s rho, NS: Not significant, *p < 0.05, **p < 0.001, *** p < 0.0001

^aWilcoxon signed rank test (paired) for comparison of entire distribution with measured creatinine

Bias: mean difference between estimated and measured creatinine. To estimate fixed bias, we compared value of the difference to a value of 0 using a one sample t-test

Precision: one standard deviation of the Bias

Proportional bias: the slope of the regression line of the differences between estimated and measured creatinine against the average of estimated and measured creatinine. A slope of 0 means no proportional bias

Accuracy reflects the percentage of estimated SCr within 10 or 30% of the measured SCr, where accuracy = [(measured SCr- estimated SCr)/measured SCr] *100

P value is the significance of the deviation of the slope from 0. ***p < 0.0001