Accuracy and reproducibility of a new contrast clearance method for the determination of glomerular filtration rate.

Abstract

A new method for determining the glomerular filtration rate was analysed prospectively. The method uses an x ray fluorescence technique to measure disappearance from the plasma of injected non-ionic iodinated contrast media. Eighty seven patients were studied. Fifty four had an intravenous dose of 100 ml iohexol (Omnipaque) and 33 had 50 ml iohexol. Clearances of chromium-51 labelled edetic acid ("Cr-EDTA) were measured simultaneously. In the patients given 100 ml iohexol there was excellent correlation with 5"Cr-EDTA clearance (r=0-90). The correlation using 50 ml iohexol was also good (r=0-85). Correlation between creatinine clearance and clearance of 5Cr-EDTA in 33 patients was less satisfactory (r=0'69). There were no adverse reactions to the contrast media. The equipment used for measuring contrast clearance was robust and simple to operate. Freezing plasma samples in 10 studies and re-examining them weekly for six weeks showed no significant variation in results; hence reproducibility was good.This new and accurate method for determining the glomerular filtration rate merits further study and might find a useful place in routine clinical practice. IntroductionDetermination of the glomerular filtration rate to measure renal function is often required in urological, nephrological, and general medical practice. Currently available methods include inulin clearance, radionuclide studies using chromium-51 labelled edetic acid ("Cr-EDTA) or technetium-99m labelled diethylene triamine penta-acetic acid ('Tc-DTPA), and creatinine clearance. Because of the complexities ofthe first two methods clinicians often settle for creatinine clearance or even simple plasma creatinine and urea concentrations as less accurate but more convenient measures of renal function in everyday practice. We present our evaluation of a new method for determining the glomerular filtration rate. This is based on the use ofcompact, purpose designed equipment currently known as the ELX 84 (Elementanalys AB, Sweden), which measures the disappearance from plasma of injected, non-ionic iodinated contrast media by an x ray fluorescence technique.

Estimating Kidney Function during Urography

“…(20) in an extensive study comparing XFA contrast medium clearance at three dose levels with simultaneously performed "Cr-EDTA clearance, reported slightly lower, 0.69-0.90, correlation coefficients.…”

Glomerular filtration rate estimated after multiple injections of contrast medium during angiography

“…It has been demonstrated that the plasma clearance of contrast media can be determined with x-ray fluorescence analysis after a single injection of contrast medium (2,10,11). Clearance is then calculated from the late part of the plasma contrast medium concentration curve (Fig.…”

“…The total plasma clearance after a single injection of contrast medium can readily be determined with the aid of x-ray fluorescence analysis (1, 2, 8-1 I ) and calculated by the same procedure as for single injection "Cr-EDTA clearance (2,3,10,11).…”

How Measuring Glomerular Filtration Rate? Comparison of Reference Methods

“…Iohexol measurement is also pretty stable at room temperature and at -20°C (Krutzen et al, 1984;O'Reilly et al, 1988). Measurement of iohexol by XRF method is less validated and probably less performing, especially in low plasma concentrations (O'Reilly et al, 1986;Back & Nilsson-Ehle, 1993;Effersoe et al, 1990;Brandstrom et al, 1998;Aurell, 1994). We will not discuss into details the other methods for measuring iohexol: capillary electrophoresis (Shihabi & Constantinescu, 1992) and mass spectrometry (Lee et al, 2006;Annesley & Clayton, 2009;Denis et al, 2008;Stolz et al, 2010).…”