Notable Steps in Obtaining Improved Estimates for Glomerular Filtration Rate

Knowledge of the glomerular filtration rate (GFR) is of crucial importance in the management of patients. In addition to a general evaluation of kidney function, a more precise assessment is valuable on many occasions, e.g., to detect early impairment of renal function, to allow correct dosage of drugs cleared by the kidneys, to monitor renal transplants, and to evaluate patients before use of potentially nephrotoxic radiographic contrast media. Determination of GFR with high accuracy requires the use of invasive techniques based on measuring the plasma clearance rate of injected substances that are excreted exclusively via glomerular filtration, e.g., inulin, 125I-iothalamate, iohexol, and 51Cr-EDTA. Such procedures are labor-intensive and not free of risk for the patient.The plasma or serum concentrations of endogenous substances, particularly creatinine, have been used as indicators of GFR for more than a century (1). The creatinine …