title: Accurate, fast, and convenient measurement of glomerular filtration rate in potential renal transplant donors.
abstract: BACKGROUND
  Measurement of glomerular filtration rate (GFR) is essential in the risk evaluation of potential kidney donors. The optimal method of measuring GFR involves using clearance techniques. However, clearance techniques are technically complex and time consuming. The goal of this study is to evaluate a different method of measuring GFR, one that retains the accuracy of a clearance technique and adds the convenience of a plasma creatinine measurement.
  
  
  METHODS
  Fifty subjects, including both normal and patients with different degrees of renal dysfunction, were included in the initial validation study. GFR was measured simultaneously using a continuous infusion of I-iothalamate and external radioactivity measurement after a single intravenous injection of Tc-labeled diethylenetriaminepentaacetic acid (Tc-DTPA). After validation, the renal function of 80 potential renal transplant donors was measured using only external radiation detection.
  
  
  RESULTS
  External radioactivity decreases versus time with first-order kinetics. The rate of clearance of Tc-DTPA was measured as the slope (kappa) of the natural logarithm of external radioactivity corrected for radioactive decay versus time. There was an excellent correlation between kappa and simultaneous GFR measurements done with I-iothalamate. Nonlinear regression analysis of kappa GFR values obtained in potential renal transplant donors versus frequencies indicates a mean value and variance similar to normal reported values obtained with clearance techniques. Estimated GFR and 24-hr plasma creatinine clearance underestimate GFR with greater variance.
  
  
  CONCLUSIONS
  Measurements of external whole tissue radioactivity after intravenous injection of Tc-DTPA represents an accurate, fast, and convenient way to measure total and individual kidney GFR, addressing an important concern during the risk evaluation of potential renal transplant donors.
authors.affiliation: Nuclear Medicine Division, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA. Crabito@partners.org
authors.forename: Carlos
authors.initials: C
authors.lastname: Rabito
authors.forename: Elkan F
authors.initials: EF
authors.lastname: Halpern
authors.forename: James
authors.initials: J
authors.lastname: Scott
authors.forename: Nina
authors.initials: N
authors.lastname: Tolkoff-Rubin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003404:Creatinine / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics; D007483:Iothalamic Acid / Q000493:pharmacokinetics; D007674:Kidney Diseases / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000503:physiopathology; D016030:Kidney Transplantation / Q000502:physiology*; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D018579:Patient Selection; D011859:Radiography; D012086:Reoperation / Q000706:statistics & numerical data; D012308:Risk Management; D014019:Tissue Donors; D055815:Young Adult
chemical_list: D007457:Iodine Radioisotopes; D007483:Iothalamic Acid; D003404:Creatinine