Measurement of glomerular filtration rate by the 99mTc-DTPA renogram is less precise than measured and predicted creatinine clearance

The work was devised to compare measurements of glomerular filtration rate (GFR) by technetium-99m-diethylenetriaminepentacetic acid (Tc-99m-DTPA) renogram to those by creatinine clearance (measured and predicted by Cockroft and Gault) and by inulin clearance. A total number of 65 individuals were enrolled: 15 healthy controls and 50 patients with renal disease, Compared to inulin clearance used as the gold standard, Tc-99m-DTPA overestimated at low and underestimated at high GFRs. Tc-99m-DTPA measurements were less precise than creatinine clearance except for individuals with GFR >100 ml/ min x 1.73 m(2). Measured creatinine clearance had the highest correlation coefficient with inulin clearance, 99mTc-DTPA clearance the lowest. In correlation analyses, 81.5% of the interindividual variability for measured creatinine clearance could be explained by true differences in inulin clearance; this value dropped to 59.1 and 57.4% for predicted creatinine clearance and Tc-99m-DTPA, respectively. In patients with GFR <25 ml/min x 1.73 m(2), all Tc-99m-DTPA measurements were out of the 95%, confidence interval for the inulin measurement. It can be inferred that Tc-99m-DTPA clearance from the renogram is less precise than measured and predicted creatinine clearance.