(a)

Equation	Mean estimated GFR* (mL/min/1.73 m2)
	All patients	Body mass index (kg/m2)				P for trend
		<20	20–25	25–30	>30
Creatinine 2009—age, sex, and race	88 ± 17	87 ± 18	88 ± 17	88 ± 17	89 ± 19	0.2
Cystatin C 2012—age and sex	83 ± 21	83 ± 23	85 ± 21	83 ± 20	78 ± 21	<0.001
Creatinine-cystatin C 2012 (age, sex, and race)	86 ± 19	85 ± 20	87 ± 19	86 ± 18	84 ± 20	0.02
Average of creatinine 2009 and cystatin C 2012	85 ± 17	85 ± 19	86 ± 17	85 ± 17	84 ± 23	0.03
Spline Log cystatin C	88 ± 22	89 ± 2	90 ± 22	88 ± 22	83 ± 23	<0.001
Spline Log cystatin C—age, sex, and race	82 ± 21	82 ± 23	84 ± 20	83 ± 20	77 ± 21	<0.001
Spline Log cystatin C—age, sex, and diabetes	85 ± 20	84 ± 22	86 ± 20	85 ± 20	80 ± 21	<0.001
Spline Log cystatin C—age, sex, and weight	81 ± 21	78 ± 22	82 ± 20	82 ± 20	79 ± 22	0.8

*Estimated GFR reported as mean ± SD.