Table 4.

Agreement between Measured GFR and Estimated GFR.

	CCC	TDI	CP
CockcroftGault	0.73 (0.64)	81.21 (95.40)	0.20 (0.17)
aMDRD	0.74 (0.67)	75.79 (89.23)	0.21 (0.19)
CKD_EPI	0.76 (0.68)	72.46 (85.12)	0.22 (0.19)
CKD_EPI_cisc	0.69 (0.58)	80.60 (98.95)	0.20 (0.18)
CKD_EPI_crecisc	0.82 (0.74)	54.07 (65.46)	0.29 (0.24)

The agreement between estimated by 5 creatinine and/or cystatin-C formulas and measured GFR was evaluated by specific statistics for continuous data, including the concordance correlation coefficient (CCC), total deviation index (TDI), coverage probability (CP) [X]. The CCC varies from 0 to 1 and combines meaningful components of accuracy and precision. A CCC > 0.90 reflects optimal concordance between measurements. The TDI captures a large proportion of data within a boundary for allowed differences between 2 measurements. Empirical TDI was calculated for a theoretical TDI of 10% and a CP of 90%. We defined a priori that acceptable bias between eGFR and mGFR should be at least 10%, and that 90% of the estimations should be included within these limits. This is based on previous reports and the reproducibility of measured GFR considering different methods [X]. Coverage probability varies from 0 to 1 and estimates whether a given TDI is less than a prespecified fixed percentage.