COMPARISON OF RADIONUCLIDE ESTIMATION OF GLOMERULAR-FILTRATION RATE USING TC-99M DIETHYLENETRIAMINEPENTAACETIC ACID AND CHROMIUM-51 ETHYLENEDIAMINETETRAACETIC ACID

Simultaneous measurements of the clearance rates of technetium 99m diethylenetriaminepentaacetic acid (Tc-99m-DTPA) and chromium 51 ethylenediaminetetraacetic acid (Cr-51-EDTA) were performed in 30 patients with a range of renal function (glomerular filtration rates between 9 and 120 ml/min). Using multiple blood samples, the two clearance values correlated well r = 0.991, standard error 3.9 ml/min), but DTPA clearance was systematically higher by 7.6%. For each radio-pharmaceutical, an equation was derived to correct clearance values obtained using only plasma samples taken at 2 and 4 h for the systematic error inherent in this technique compared with analysis of the complete plasma concentration-time curve. The root mean square error remaining after application of these equations was 1.9 ml/min for both the EDTA and DTPA data. The corresponding errors obtained using the equation derived by Brochner-Mortensen for EDTA plasma clearance were 2.2 ml/min and 1.9 ml/min, respectively, these values were not significantly different from those obtained using the equations derived in this study.