Comparison of slope-intercept with single plasma sample methods in estimating glomerular filtration rate using radionuclides.

To evaluate the accuracy of different single plasma sample methods (SPSM) 99m Tc-DTPA clearances and to test whether the SPSM can replace the dual plasma samples method (DPSM) in the measurement of glomerular filtration rate (GFR), we studied 430 subjects counting renal patients and donors (240 male, 190 female; mean age 43.40 ± 16.30 years). All the subjects underwent dynamic renal scintigraphy after injection of 99m Tc-DTPA; the GFR was calculated by seven SPSMs in addition to DPSM as a reference. Each of the SPSM clearance was compared with the DPSM measurement. There was a high correlation of all the SPSMs and the DPSM. The limits of agreement (95%) were found between the DPSM and all the SPSMs. Overall, the best method among the SPSMs, which is closest to the DPSM, is Fleming's single method as it has a statistically significant low mean difference (bias), low standard error, close mean ± SD to the reference method, good limits of agreement and high correlation co-efficient. This study concludes that, among the SPSMs, Fleming can reflect GFR more accurately than other methods, particularly when the expected serum creatinine is normal.