Measurement of renal function and estimation of GFR

At a glance

• GFR is the best overall index of kidney function. Normal in a young adult is about 120 mL/min/1.73 m², falling by roughly 1 mL/min/year after 40.
• GFR can't be measured at the bedside. It's either measured as the clearance of an exogenous filtration marker (inulin, iohexol, ⁵¹Cr-EDTA, ⁹⁹ᵐTc-DTPA) or estimated from an endogenous marker (creatinine, cystatin C).
• Every estimating equation assumes steady state and an average relationship between marker production and body size. Paper 1 tests the situations where those assumptions fail.