ABSTRACT
Glomerular filtration rate (GFR) is a unit of measure of kidney excretory function. It is usually expressed as mL/min, and is approximately 125 mL/min or 180 L/day. The classification of chronic kidney disease is largely based on calculated or estimated GFR. GFR can either be calculated using the plasma clearance of a suitable substance, by applying the Fick principle or estimated using prediction formulae based on factors such as the patient’s age, sex and serum creatinine level. The modification of diet in renal disease study is the most validated formula for eGFR and used in most laboratories. The use of inulin is limited because of its expense and impracticalities. Insulin is used mostly for research, where very accurate assessments of GFR are required. In practice, creatinine clearance is no longer used to measure GFR, as a 24-hour urine collection is required, which is impractical for patients and leads to inaccuracies in measurement.
