Table 4. Correlation of pre-dialysis Cystatin C and β2 microglobulin plasma levels and their interdialytic rise with various measures of RKF.

		Cystatin C	β2 microglobulin	1/Cystatin C	1/ β2 microglobulin	Interdialytic rise in Cystatin C	Interdialytic rise in β2 microglobulin
	Pearson Correlation	-0.66	-0.72	0.71	0.82	-0.56	-0.69
GFRResidual (ml/min/1.73m2)	r2	0.433	0.517	0.503	0.672	0.311	0.482
	Sig. (p)	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001
	Pearson Correlation	-0.62	-0.69	0.66	0.76	-0.53	-0.67
Urea clearance (ml/min/1.73m2)	r2	0.39	0.47	0.44	0.57	0.28	0.44
	Sig. (p)	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001
	Pearson Correlation	-0.62	-0.68	0.69	0.82	-0.53	-0.66
Creatinine clearance (ml/min/1.73m2)	r2	0.39	0.46	0.48	0.68	0.28	0.44
	Sig. (p)	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001

GFR_Residual = the measured residual GFR (mean of urea and creatinine clearances).r² is the square of the Pearson correlation coefficient.