Table 2.

Accuracy of models for estimating reference mGFRs for all observations and for consistent mGFRs only

	MDRD Study				AASK				MDRD Study + AASK
	1-P30		RMSE		1-P30		RMSE		1-P30		RMSE
	All GFRs	Consiste nt mGFRs^	All GFRs	Consisten t mGFRs^	All GFRs	Consisten t mGFRs^	All GFRs	Consiste nt mGFRs^	All GFRs	Consiste nt mGFRs^	All GFRs	Consisten t mGFRs^
Single mGFR as reference test
Sample Size	1046	906	1046	906	949	840	949	840	1995	1746	1995	1746
MDRD Study eqn*	8.8%	7.6%‡,b	0.180	0.174‡,b	15.8%	14.9%	0.193	0.186	12.1%	11.1%‡,b	0.196	0.188‡,b
CKD-EPI SCysC eqn**	17.2%	14.7%‡‡,b	0.219	0.209‡,b	17.2%	15.4%‡‡,b	0.196	0.190	17.1%	15.0%‡‡,b	0.223	0.211‡,b
CKD-EPI SCr & SCysC eqn***	6.7%	4.7%‡‡,b	0.165	0.157‡,b	10.1%	8.8%‡,b	0.173	0.163	8.3%	6.7%‡‡,b	0.180	0.169‡‡,b
Prerandomization mGFR eqn	8.9%	---1	0.170	---1	6.9%	---1	0.146	---1	8.0%	---1	0.167	---1
Average of 2 mGFRs as reference test
Sample Size	1046	906	1046	906	949	840	949	840	1995	1746	1995	1746
MDRD Study eqn	9.1%	7.7%‡‡,b	0.173†,a	0.168†,a	14.6%	13.5%‡,b	0.188	0.184‡,b	11.7%	10.5%‡‡,b	0.186††,a	0.181††,a,‡,b
CKD-EPI SCysC eqn	13.7%††,a	13.1%†,a	0.201††,a	0.198††,a	15.4%†,a	14.3%‡,b	0.193	0.190	14.5%††,a	13.7%†,a,‡ ,b	0.206††,a	0.203††,a,‡,b
CKD-EPI SCr & SCysC eqn	5.3%†,a	4.3%‡,b	0.155††,a	0.149††,a,‡, b	8.3%†,a	7.0%†,a,‡‡,b	0.166†,a	0.160‡,b	6.7%†,a	5.6%†,a,‡‡,b	0.166††,a	0.160††,a,‡‡, b
Average of 3 mGFRs as reference test
Sample Size	764	632	764	632	504	341	504	341	1268	973	1268	973
MDRD Study eqn	6.9%	5.4%‡,b	0.162†,a	0.155‡,b	14.7%	12.9%	0.189	0.176	10.0%	8.0%‡‡,b	0.179†,a	0.168‡,b
CKD-EPI SCysC eqn	12.0%	11.4%	0.187†,a	0.181†,a	15.7%	14.7%	0.197	0.186	13.5%	12.5%	0.196††,a	0.189
CKD-EPI SCr & SCysC eqn	4.2%	3.3%‡,b	0.144†,a	0.136†,a,‡,b	7.9%	5.0%†,a,‡,b	0.168	0.149	5.7%	3.9%‡‡,b	0.159††,a	0.146†,a,‡,b

¹Biased estimate because the pre-randomization mGFR (non-reference visit) was also used to define consistent GFRs.

^†p< 0.05

^††p< 0.001

^aP values measured in a paired test compared to the same model when a single mGFR is used as the reference in the same population sample. 1-P₃₀ tested using McNemar chisquare for paired proportions (for example using the CKD-EPI SCysC equation model in the combined population, 1-P₃₀=14.5% when the average of 2 mGFRs is the reference test versus 17.1% when single mGFR is the reference test [p<0.0001]; when using the CKD-EPI SCysC model in the combined population, 1-P₃₀=13.5% when the average of 3 mGFRs is the reference test versus 10.6% in the CKD-EPI SCysC model limited to the 1268 participants with 3 GFRs and for which a single mGFR is the reference test [P=0.07]). RMSE tested using paired t-test of the squared residuals

^‡p< 0.05

^‡‡p< 0.001

^bComparison of individuals with consistent and inconsistent mGFRs. 1-P₃₀ tested using chi-square (for example, when the average of 2 mGFRs is the reference test, using the CKD-EPI SCysC equation model in the combined population, 1-P₃₀=13.7% when limited to the 1746 with consistent mGFRs versus 20.1% in the 249 participants with the inconsistent GFRs [p=0.02], leading to an overall 1-P₃₀ of 14.5% in all GFRs). RMSE tested using unpaired t-test of the squared residuals. Symbols are placed in the consistent mGFRs’ column.

^*The MDRD Study equation is eGFR_MDRD =175×standardized Scr ^−1.154×age^−0.203×1.212[if black]×0.742[if female]

^**CKD-EPI SCysC equation is eGFR_CKD-EPIcys = 127.7 × SCysC^−1.17 × age-0.13 × 0.91 [if female] × 1.06 [if black]

^***the CKD-EPI SCr-SCysC is eGFR_{CKD-EPI Scr+SCysC}= 177.6 × Scr^−0.65 × SCysC^−0.57 × Age^−0.20 × 0.82 [if female] and 1.11 [if black])

^{^}consistent mGFRs excludes those which differed from the reference mGFR by 25% or more

Abbreviations and definitions: eqn, equation; P30, percentage of estimated GFR within 30% of the gold standard reference test; root mean squared error (RMSE); measured glomerular filtration rate (mGFR); Modification of Diet in Renal Disease (MDRD) Study; Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI); AASK, African American Study of Kidney Disease