Limitations of the single sample tracer method for determining glomerular filtration rate.

Apparent volumes of distribution of 51Cr-EDTA and 99Tcm-DTPA were calculated three hours after intravenous injection and correlated with simultaneous estimation of GFR. A reasonable correlation between these values was obtained for those patients with GFR greater than 50 ml/min (standard error of estimate using 51Cr-EDTA 7.6 ml/min and 99Tcm-DTPA 13.7 ml/min). Theoretical reasons are given why a single sample technique will not be accurate over a wide range of renal function.