GLOMERULAR-FILTRATION RATE MEASUREMENT - A NEGLECTED TEST IN UROLOGICAL PRACTICE

Objectives To assess the accuracy and reproducibility of methods used to measure glomerular filtration rate (GFR) in clinical practice. Pati ents and methods Simultaneous clearances of iohexol, Tc-99m-diethylene -triamine-penta-acetic acid (DTPA), 24 h renal creatinine clearance an d creatinine clearance estimated from a serum sample only, were obtain ed in 31 patients. Accuracy was calculated relative to iohexol clearan ce. The reproducibility of each method was determined by repeat measur ements in the same individuals: three Tc-99m-DTPA clearances in 21 pat ients; three 24 h creatinine clearance estimations in 12 patients: and three serum creatinine clearance estimations in 21 patients. Results The mean differences between Tc-99m-DTPA clearance, 24 h renal creatin ine clearance and estimated creatinine clearance compared with the ref erence method were 0.2 mL/min, 21.6 mL/min and 0.6 mL/min, respectivel y. (TC)-T-99m-DTPA clearance had fairly tight 95% limits of agreement (12.2 mL/min) compared with 35.4 mL/min for 24 h creatinine clearance and 25.8 mL/min for estimated creatinine clearance. The reproducibilit y for each method was 5.4%, 24.3% and 6.1%, respectively. Conclusion S ingle-injection Tc-99m-DTPA clearance provides an accurate and reprodu cible method of GFR measurement that is suitable for objective monitor ing of renal function, Twenty-four hour creatinine clearance is neithe r sufficiently accurate nor reproducible for this purpose, Creatinine clearance estimation from a serum sample without urine collection may be preferable to the more traditional 24 h collection method.