Estimation of glomerular filtration rate by using tc-99m DTPA plasma I sample method, Gates method, Cockcroft-Gault method and predicted creatinine clearance method: a prospective comparative analysis with plasma 2 - sample clearance method

ABSTRACT

To compare diagnostic accuracy of predicted clearance method, Gates method. Cockcroft-Gault method and plasma 1-sample clearance method with plasma 2-samples clearance method with Tc-99m DTPA for the estimation of glomerular filtration rate[GFR]. This study included 91 consecutive patients who were referred for evaluation of renal function to the Nuclear Medicine section of Karachi Institute of Radiotherapy and Nuclear Medicine [KIRAN] from September 2004 to September 2005. The GFR was determined simultaneously by 5 methods including Plasma two-Sample Clearance method after Tc-99m DTPA injection [PSC 2]; Plasma one-Sample Clearance method after Tc-99 m DTPA injection [PSC I]; Gamma camera uptake method after Tc-99m DTPA injection [Gates method]; Predicted Creatinine Clearance by Modification of Diet and Renal Diseases [MDRD] and Cockeroft-Gault's equation for GFR estimation [CG]. PSC 2 was chosen as a reference, Out of the 91 patients, 71 were males and 20 females with age ranging from 16-68 years. The regression equation of the PSC 1, Gates, MDRD and CC method against the NC 2 was Y = 1.884+0.970X [r=0.90, p<0.001, SEE value-10, 23 ml/min/1.73m2]. Y = - 9.944 + l.083X [r=0.82, p<0.001, SEE valuel=11.02 mI/min/1.73m2], Y=25.606+0.640X [r=0.71, <0.002, SEEvaIuc=15.56 ml/min/1.73m2], and Y=14.9811-0.714X [r=0.77, p=0.002, SEE value=14.44 mI/min/1.73m2] respectively. In comparison with the GFR by PSC 2, the PSC I and Gates tended to overestimate by 1% [p=0.359] and 2% [p=0.265] respectively, MDRD and CC tended to underestimate GER by 11% and 14% respectively [p<0.001] PSC I correlate well with PSC 2 and either can be substituted for the other as ideal GFR markers. The Gates method shows good correlation with PSC 2 however it is less precise than PSC I. MDRD and CG methods due to significant underestimation are not considered as ideal GFR marker