RESUMEN
The gamma camera uptake method with Tc-99m-DTPA (diethylenetriaminepentaacetic acid) is a simple method for determination of glomerular filtration rate (GFR), and is less time-consuming than other methods, but its diagnostic accuracy is debated. Gate's method (low-dose; LD), the high-dose method (HD), the predicted-clearance method, and the plasma-clearance method with Tc-99m-DTPA are compared in this study. We also performed GFR measurement and diuretic renography simultaneously. Tc-99m DTPA renography was performed in 36 patients aged 18-72 years with a wide range of renal function (serum creatinine 1.37 +/- 0.49 mg/dl). GFR was determined by four methods: the gamma camera uptake method with low-dose Tc-99m DTPA (Gates, LD); the gamma camera uptake method with high-dose Tc-99m DTPA (HD); the predicted creatinine clearance method (Cockcroft-Gualt, CG); and the plasma sample clearance (PSC) method using a mono-exponential curve. The PSC method was chosen as reference. The regression equations for the CG, Gates (low-dose), and HD methods against the PSC method were 28.68 + 0.80X (r = 0.72; P value < 0.0001, RMSE = 21.65 ml/min/1.73 m(2)), 6.19 + 0.79X (r = 0.90; P value < 0.0001, RMSE = 10.64 ml/min/1.73 m(2)), and 6.53 + 0.88X (r = 0.93; P value < 0.0001, RMSE = 9.35 ml/min/1.73 m(2)), respectively. In comparison with determination of GFR by the PSC method, the CG method tended to overestimate GFR while, perversely, the LD and HD methods tended to underestimate GFR. The three methods were in agreement with the PSC method but the high-dose GFR method resulted in less error in estimation of GFR. Furthermore, GFR measurement and diuretic renography could be performed at the same time when the high-dose method was used. Because of the low cost and negligible radiation burden, this method might be preferred for routine practice in nuclear medicine.