title: Reproducibilities and responses to food intake of GFR measured with chromium-51-EDTA and iohexol simultaneously and independently in normal subjects.
abstract: BACKGROUND
  The aim was to evaluate the reproducibility of glomerular filtration rate (GFR) measured with iohexol and its response to food in a direct and independent comparison with Cr-51-ethylenediaminetetraacetic acid (EDTA), and examine the influence of two different whole body scaling parameters, body surface area (BSA) and extracellular fluid volume (ECV).
  
  
  METHODS
  Fasting and non-fasting GFR were measured in 20 normal volunteers using Cr-51-EDTA and iohexol, simultaneously injected into opposite arms. In 10, the fasting study was repeated. Venous samples obtained bilaterally 20, 40, 60, 120, 180 and 240 min after injection were assayed for indicator injected contralaterally-Cr-51-EDTA by well-counting and iohexol by X-ray fluorescence. GFR scaled to BSA was measured from six samples (GFR/BSA6) and from the last three (GFR/BSA3). GFR scaled to ECV was calculated as the mean transit time of marker using six samples (GFR/ECV6) or the last three (GFR/ECV3).
  
  
  RESULTS
  GFR/BSA3 was reproducible (coefficient of variations of 7.4% for Cr-51-EDTA and 7.6% for iohexol). Using Cr-51-EDTA, GFR/ECV3 (9.1%) and GFR/ECV6 (7.7%) were as reproducible as GFR/BSA3 and GFR/BSA6 (both 8.1%). However, GFR/ECV3 measured with iohexol had poorer reproducibility (16.8%). Food resulted in an increase in scaled GFR of about 5 ml/min but this was statistically significant only with respect to GFR/BSA (measured with Cr-51-EDTA or iohexol) and not GFR/ECV.
  
  
  CONCLUSIONS
  Measured with Cr-51-EDTA, but not iohexol, GFR/ECV was as reproducible as GFR/BSA. GFR/BSA, measured with Cr-51-EDTA or iohexol, but not GFR/ECV, significantly increased after food.
authors: Department of Nuclear Medicine, Addenbrooke's Hospital, Cambridge.
authors: Nicholas J
authors: NJ
authors: Bird
authors: Christina
authors: C
authors: Peters
authors: A Robert
authors: AR
authors: Michell
authors: A Michael
authors: AM
authors: Peters
mesh_terms: D000328:Adult; D002860:Chromium Radioisotopes; D015331:Cohort Studies; D004435:Eating; D004492:Edetic Acid / Q000493:pharmacokinetics*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007472:Iohexol / Q000493:pharmacokinetics*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D002860:Chromium Radioisotopes; D007472:Iohexol; D004492:Edetic Acid