Comparison between total and renal plasma clearance of [51Cr] EDTA.

The total plasma (Et) and renal plasma (Er) clearances of [51Cr]EDTA were measured simultaneously in 40 patients with a wide range of renal function. The regression equation was Et identical to 0.997 Er+4.1; the slope of the regression line was not significantly different from 1.00, and the intercept differed significantly from zero. The results suggest that [51Cr]EDTA has a significant extrarenal clearance of approximately 4 ml/min, independent of renal function. The data are used to correct the total [51Cr]EDTA plasma clearance, measured by a simplified method, to yield a rapid, accurate, and precise measurement of glomerular filtration rate for routine clinical use.