GFR measurement with iohexol and 51Cr-EDTA. A comparison of the two favoured GFR markers in Europe

Nephrol Dial Transplant. 1998 May;13(5):1176-82. doi: 10.1093/ndt/13.5.1176.


Background: The aim of the present study was to compare the most commonly used GFR markers for clearance measurements, 51Cr-EDTA and iohexol, using two different methods for iohexol analysis, HPLC and X-ray fluorescence, referring both to the multiple-sample and single-sample calculations, using 51Cr-EDTA as the reference method.

Methods: Forty-nine patients with an estimated GFR >40 ml/min were included. 51Cr-EDTA and iohexol were injected simultaneously and blood samples were taken 150, 195 and 240 min after injection of the respective marker.

Results: The multiple-point clearances, determined from HPLC and X-ray fluorescence, compared to 51Cr-EDTA correlated highly (r=0.92 and 0.95 respectively). The results from single-point clearance comparison, iohexol measured by HPLC vs 51Cr-EDTA, yielded a correlation of r=0.91, while single-point clearance from iohexol, analysed by X-ray fluorescence, obtained a correlation of 0.93 and an intercept statistically different from origo.

Conclusions: Iohexol and 51Cr-EDTA are comparable as GFR markers for multiple-point clearance measurements. The single-sample method for GFR >40 ml/min can be used with a high accuracy. The precision and accuracy of X-ray fluorescence analysis of low concentrations of iohexol were less than those of HPLC. Care should therefore be taken when using X-ray fluorescence that the injected dose of iohexol should result in a plasma concentration level of iodine of at least 0.06 mg/ml at the time of blood sampling.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Biomarkers / analysis
  • Chromatography, High Pressure Liquid
  • Chromium Radioisotopes
  • Edetic Acid*
  • Europe
  • Evaluation Studies as Topic
  • Female
  • Glomerular Filtration Rate* / physiology
  • Humans
  • Iohexol*
  • Male
  • Middle Aged
  • Spectrometry, X-Ray Emission


  • Biomarkers
  • Chromium Radioisotopes
  • Iohexol
  • Edetic Acid