Journal of the Dow University of Health Sciences (Feb 2015)
ESTIMATION OF GLOMERULAR FILTRATION RATE BY USING TC-99M DTPA PLASMA 1 SAMPLE METHOD, GATES METHOD, COCKCROFT-GAULT METHOD AND PREDICTED CREATININE CLEARANCE METHOD: A PROSPECTIVE COMPARATIVE ANALYSIS WITH PLASMA 2 - SAMPLE CLEARANCE METHOD.
Study Objective: 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).Study Design: Comparative study. Materials and Methods: This study included 91 consecutive patients who were referred for evaluation ofrenal 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 methodsincluding Plasma two-Sample Clearance method after Tc-99m DTPA injection (PSC 2); Plasma one-SampleClearance method after Tc-99 m DTPA injection (PSC 1); Gamma camera uptake method after Tc-99mDTPA injection (Gates method); Predicted Creatinine Clearance by Modification of Diet and Renal Diseases(MDRD); and Cockcroft-Gaultâ€™s equation for GFR estimation (CG). PSC 2 was chosen as a reference. Results: Out of the 91 patients, 71 were males and 20 females with age ranging from 16-68 years. Theregression equation of the PSC 1, Gates, MDRD and CG method against the PSC 2 was Y = 1.884 +0.970X(r=0.90, p<0.001, SEE value=10.23 ml/min/1.73m2), Y = - 9.944 + 1.083X (r=0.82, p<0.001, SEE value=11.02ml/min/1.73m2), Y =25.606+ 0.640X (r=0.71, p=0.002, SEE value=15.56 ml/min/1.73m2), and Y =14.981+0.714X (r=0.77, p=0.002, SEE value=14.44 ml/min/1.73m2) respectively. In comparison with the GFR byPSC 2, the PSC 1 and Gates tended to overestimate by 1% (p=0.359) and 2% (p=0.265) respectively, MDRDand CG tended to underestimate GFR by 11% and 14% respectively (p<0.001). Conclusions: PSC 1 correlate well with PSC 2 and either can be substituted for the other as ideal GFRmarkers. The Gates method shows good correlation with PSC 2 however it is less precise than PSC 1. MDRDand CG methods due to significant underestimation are not considered as ideal GFR marker.