Table 3.

Accuracies and absolute bias for the different equations (true GFR assessed by inulin clearance, means ± SD: 101 ± 32 ml/min per 1.73 m²)

A. Equations using serum creatinine
	Local Schwartz	Schwartz 1976	Schwartz 2009
eGFR means ± SD (ml/min per 1.73 m2)	100 ± 39	151 ± 58c	109 ± 44c
iGFR-eGFR means ± SD (ml/min per 1.73 m2)	1 ± 26	−50 ± 40	−8 ± 29
Accuracy 10% (%)	39	4	38
Accuracy 30% (%)	91	23	84
Accuracy 50% (%)	99	54	96
Correlation coefficient between eGFR and iGFR	0.789b	0.784b	0.779b

B. Equations using serum cystatin C
	Hoek	Le Bricon	Larsson	Rule	Filler	Zappitelli
eGFR means ± SD (ml/min per 1.73 m2)a	94 ± 27c	99 ± 26	100 ± 34	97 ± 31c	115 ± 35c	96 ± 31c
iGFR-eGFR means ± SD (ml/min per 1.73 m2)a	7 ± 19	2 ± 19	0 ± 21	4 ± 19	−14 ± 21	4 ± 19
Accuracy 10% (%)	47	46	45	47	28	48
Accuracy 30% (%)	91	90	87	91	81	91
Accuracy 50% (%)	98	98	97	98	95	98
Correlation coefficient between eGFR and iGFR	0.784b	0.784b	0.784b	0.784b	0.784b	0.784b

C. Combined equations using both plasma creatinine and serum cystatin C
	Bouvet	Zappitelli
eGFR means ± SD (ml/min per 1.73 m2)a	79 ± 24c	108 ± 38c
iGFR-eGFR means ± SD (ml/min per 1.73 m2)a	21 ± 26	−7 ± 20
Accuracy 10% (%)	22	40
Accuracy 30% (%)	62	91
Accuracy 50% (%)	95	98
Correlation coefficient between eGFR and iGFR	0.570b	0.838b

^aExcept for Larsson and Bouvet formula (ml/min).

^bP < 0.001, Spearman correlation.

^cP < 0.05, Wilcoxon paired test in comparison with inulin clearance.