Reliability of routine clearance methods for assessment of glomerular filtration rate in advanced renal insufficiency

The reliability of different clearance methods to assess the glomerular filtration rate (GFR) was tested in fifteen patients with advanced chronic renal failure (range of GFR: 3-13 ml/min). The renal [51Cr]EDTA plasma clearance (Er) measured during optimal conditions with determination of residual bladder-urine was used as reference parameter of GFR and the reliability (+/-) of a thus corrected value to assess GFR of the individual patient are given in parenthesis. The arithmetic mean of the renal plasma clearance of endogenous creatinine (Clcreat) and urea (2.0 ml/min; +/- 1.5 ml/min); single determination of 25-h clcreat (3.4 ml/min; +/- 2.0 ml/min); Clcreat calculated from a measured plasma creatinine concentration, considering sex, age and body weight of the patient (2.9 ml/min; +/- 2.3 ml/min); total [51Cr]EDTA plasma clearance (Et) determined form three blood samples drawn 3-5 h after i.v. single injection 93.7 ml/min; +/- 2.2 ml/min); and Et determined form two blood samples drawn 4 and 24 h after i.v. injection (0.5 ml/min; +/- 0.5 ml/min). It is concluded that the most reliable assessment of GFR (=Er) is achieved either form a direct measurement or indirectly from Et determined from two blood samples drawn 5 and 24 h after i.v. single injection. use of the mean value of three 25-h Clcreat determinations is recommended if facilities for measurement of radioactivity are not available.