Table 3.

Center effects on start of kidney replacement therapy

Center effect	Any KRT	Dialysis	Preemptive Tx
P-value	<0.001	<0.001	<0.001
Explained variation ΔR2D	6.4%	6.8%	8.7%
HR Top 15%	1.85	2.22	2.71
HR Min 15%	0.54	0.45	0.37

HR, hazard ratio; KRT, kidney replacement therapy; Tx, kidney transplant.

Confounding at center level was investigated using a frailty term. The impact of the center was determined by variation R²_D. Second quantification of the center effect is shown as HR for the 15% of centers with the highest and lowest center effect respectively.