Table 2.

Fractional excretion of inulin, creatinine, d-asparagine, and d-serine based on various standard molecules

Substrate for FE	Inulin-based FE	Creatinine-based FE	d-Asparagine-based FE
Inulin	100.00 (Ref)	68.84 (67.81–69.87)	104.68 (102.42–106.93)
Creatinine	147.93 (145.39–150.46)	100.00 (Ref)	152.60 (149.75–155.45)
d-Asparagine	98.67 (96.43–100.90)	66.97 (65.68–68.25)	100.00 (Ref)
d-Serine	84.84 (83.22–86.46)	57.75 (56.70–58.75)	87.22 (85.54–88.90)
Cystatin C	–	< 0.520	–

FE, fractional excretion.

FE values for the substrate were calculated based on inulin, creatinine, and d-asparagine. Data, % (95% confidence interval).