Selection of routine method for determination of glomerular filtration rate in adult patients

The precision and reporducibility of three different clearance methods as used in clinical routine assessment of glomerular filtration rate (GFR) were investigated in 51 patients: total [51Cr]EDTA plasma clearance (E); 24-hr endogenous creatinine clearance (C); and creatinine clearance estimated from the plasma creatinine concentration, weight, and sex- and age-dependent mean creatinine excretion rate (c). The precision and reporducibility (coefficient of variation) for single determinations were, in patients with E greater than 30 ml/min, 5.5 and 4.1% (E); 26.9% (C); and 23.2 and 11.0% (c). The corresponding figures for E less than 30 ml/min were 11.6 and 11.5% (E); 21.9% (C); and 21.4 and 6.5% (c). The precision of C could not be ameliorated by excluding single deviating determinations, but only by excluding patients for whom the precision of 15.5% for mean of three determinations of C (total material) could be reduced to 10% by excluding 25% of the patients. The present data indicate that E in most cases is the method of choice for assessment of GFR in clinical routine work. For changes in renal function, especially at low functional levels, c may be of value.