Experimental Factor Ontology id EFO_0007934 (creatinine clearance measurement) can be described as follows. The clearance rate of creatinine, that is, the volume of plasma that is cleared of creatinine by the kidneys per unit time. Creatinine clearance is calculated using the level of creatinine in a sample of urine, usually one collected over a period of 24 hours, the corresponding plasma creatinine level, and the volume of urine excreted. It is used as an approximation of the glomerular filtration rate (GFR).