TA COMPARISON OF THE CREATININE CLEARANCE BY GFR ESTIMATING EQUATIONS WITH MEASURED GFR BY ISOTOPE SCAN IN VOLUNTARY LIVING KIDNEY DONOR

Abstract

Background: Glomerular filtration rate (GFR) is essential for renal function evaluation. The need for estimating GFR stems from the shortcomings of interpreting plasma creatinine alone, the cost and complexities of determining a gold standard GFR with either inulin or radionuclides like iothalamate, and the inaccuracies associated with the measurement of a 24 h urine creatinine clearance. It is of special concern in Voluntary Kidney Donor(VKD) in living donor transplantation. Equations like Cockcroft- Gault formula (CGF), Modified Diet in Renal Disease (MDRD) and the Chronic kidney disease- Epidemiology Collaboration equation (CKD-EPI) are useful in estimating GFR. This study is to validate the different GFR estimating equations, and their correlation with measured GFR by nuclear Isotope scan in VKD. Methods: We measured GFR with double-sample plasma clearance of 99mTc-DTPA (mGFR) in 814 healthy adult (=>18yrs) individuals. Using mGFR as the gold standard, we evaluated the efficiency of three different GFR estimation equations (CGF, MDRD and CKD-EPI) and calculated their precision and correlation. Result: In our population, the mean mGFR was 81.46 ± 14.35 mL/min/1.73m2. In correlation analysis, the three equations have significant linear correlation with mGFR (p<0.01), and the linear regression demonstrated moderate explanatory capacity of eGFR produced by CKD-EPI (R2 = 0.22), CGF (R2 = 0.15) and MDRD (R2 = 0.12). The slopes in the Bland-Altman analysis of CGF, MDRD and CKD-EPI are -0.68, -0.41 and -0.18. Intraclass coefficients was highest for CKD-EPI (0.63), followed by CGF (0.51) and MDRD (0.49). Thus, The CGF, MDRD and CKD-EPI formula produced eGFR with strong correlation with mGFR, moderate explanation capacity of variance in mGFR, small bias, satisfactory performance in Bland-Altman analysis and high intra-class correlation coefficients. Conclusion: This study concludes significant correlation between measured GFR and the GFR estimating equations: CGF, CKD EPI and MDRD. Of the three, CKD -EPI has the highest precision of GFR prediction in VKD.