title: Glomerular filtration rate measurement: a neglected test in urological practice.
abstract: OBJECTIVE
  To assess the accuracy and reproducibility of methods used to measure glomerular filtration rate (GFR) in clinical practice.
  
  
  METHODS
  Simultaneous clearances of iohexol, 99mTc-diethylene-triamine-penta-acetic acid (DTPA), 24 h renal creatinine clearance and creatinine clearance estimated from a serum sample only, were obtained in 31 patients. Accuracy was calculated relative to iohexol clearance. The reproducibility of each method was determined by repeat measurements in the same individuals: three 99mTc-DTPA clearances in 21 patients; three 24 h creatinine clearance estimations in 12 patients; and three serum creatinine clearance estimations in 21 patients.
  
  
  RESULTS
  The mean differences between 99mTc-DTPA clearance, 24 h renal creatinine clearance and estimated creatinine clearance compared with the reference method were 0.2 mL/min, 21.6 mL/min and 0.6 mL/min, respectively. 99mTc-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 reproducibility for each method was 5.4%, 24.3% and 6.1%, respectively.
  
  
  CONCLUSIONS
  Single-injection 99mTc-DTPA clearance provides an accurate and reproducible method of GFR measurement that is suitable for objective monitoring of renal function. Twenty-four hour creatinine clearance is neither 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.
authors.affiliation: Department of Urology, Stepping Hill Hospital, Stockport, UK.
authors.forename: S C
authors.initials: SC
authors.lastname: Brown
authors.forename: P H
authors.initials: PH
authors.lastname: O'Reilly
mesh_terms: D003404:Creatinine / Q000378:metabolism; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007472:Iohexol / Q000378:metabolism; D004369:Pentetic Acid / Q000378:metabolism; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D007472:Iohexol; D004369:Pentetic Acid; D003404:Creatinine