GFR measurement with iohexol and 51Cr-EDTA. A comparison of the two favoured GFR markers in Europe.
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.
Brändström
E
E
Department of Clinical Physiology, Sahlgrenska University Hospital, Göteborg, Sweden.
Grzegorczyk
A
A
Jacobsson
L
L
Friberg
P
P
Lindahl
A
A
Aurell
M
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D002860:Chromium Radioisotopes; D004492:Edetic Acid; D005060:Europe; D005069:Evaluation Studies as Topic; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology; D006801:Humans; D007472:Iohexol; D008297:Male; D008875:Middle Aged; D013052:Spectrometry, X-Ray Emission
D015415:Biomarkers; D002860:Chromium Radioisotopes; D007472:Iohexol; D004492:Edetic Acid