Table 2 Pearson correlations between different markers of GFR.

			*Plasma creatinine	Cystatin C	*β2‐microglobulin		*Cockcroft‐Gault GFR		MDRD GFR	*Calculated CC clearance		Measured Ccr
			(μmol/l)	(mg/l)	(mg/l)		(ml/min)		(ml/min/1.73 m2)	(ml/min/1.73 m2)		(ml/min)
(A) Uncorrected
Plasma creatinine (µmol/l)		r
		p
Cystatin C (mg/l)		r	0.050
		p	0.732
β2‐Microglobulin (mg/l)		r	0.331	0.677
		p	0.028	<0.0001
Cockcroft‐Gault GFR		r	−0.699	−0.107	−0.269
(ml/min)		p	<0.0001	0.475	0.081
MDRD GFR		r	−0.802	−0.182	−0.348		0.783
(ml/min/1.73 m2)		p	<0.0001	0.217	0.021		<0.0001
Calculated CC clearance		r	−0.239	−0.663	−0.469		0.117		0.276
(ml/min/1.73 m2)		p	0.167	<0.0001	0.004		0.517		0.115
Measured Ccr (ml/min)		r	−0.207	−0.150	−0.033		0.434		0.271	0.271
		p	0.256	0.413	0.864		0.015		0.134	0.222
(B) After correction for sex
Plasma creatinine (μmol/l)		r
		p
Cystatin C (mg/l)		r	0.044
		p	0.767
β2‐Microglobulin (mg/l)		r	0.339	0.677
		p	0.026	<0.0001
Cockcroft‐Gault GFR		r	−0.739	−0.106
(ml/min)		p	<0.0001	0.482	0.086
MDRD GFR		r	−0.803	−0.180	−0.346		0.791
(ml/min/1.73 m2)		p	<0.0001	0.226	0.023		<0.0001
Calculated CC clearance		r	−0.147	−0.687	−0.480		0.115		0.236
(ml/min/1.73 m2)		p	0.408	<0.0001	0.004		0.532		0.186
Measured Ccr (ml/min)		r	−0.272	−0.154	−0.039		0.441		0.301	0.328
		p	0.138	0.407	0.845		0.015		0.100	0.147

*Log transformed before analysis.

CC, cystatin C; Ccr, creatinine clearance; GFR, glomerular filtration rate; MDRD, modified Modification of Diet in Renal Disease.