Comparison of Different Equations with GFR Measured by Scintigraphy in Kidney Donors

Technetium-99^m diethylene-triamine-pentaacetate (99^mTc-DTPA)-based scintigraphy is a convenient way to assess measured glomerular filtration rate (mGFR) in kidney donors. Equations have been developed to calculate GFR in the general population. This study aims to identify the best among commonly employed equations to better predict GFR when compared with scintigraphy-based mGFR. Also, the trends in mGFR values were studied over 1 year post-donation.

Thirty-four kidney donors were recruited for this study from November 2017 to November 2018 and followed-up for a year. Estimated GFR (eGFR) was calculated using the Modification of Diet in Renal Disease (MDRD) Equation, Chronic Kidney Disease Epidemiology (CKD-EPI) Collaboration equation, and Nankivell formula; the values were compared to that obtained using 99^mTc-DTPA both pre-and post-donation. Correlation and agreement between the eGFR and mGFR were studied using Statistical Package for the Social Sciences (SPSS) version 23.0 and Microsoft Excel.

mGFR was augmented by 32.3 ± 27.8% in the remnant kidney post-donation. The baseline mGFR, post-donation mGFR, and the quantum of its increase post-donation did not differ between overweight donors and donors with normal body mass index (BMI). mGFR correlated poorly with all the eGFR equations both pre- and post-donation. Bland-Altman analysis showed weak agreement with significant bias and variance between mGFR and all eGFR equations.

In Indian kidney donors, mGFR by 99^mTc-DTPA scintigraphy shows poor correlation and agreement with the commonly used eGFR equations. An individualized approach is needed to assess the kidney function of live donors to minimize harm to both the recipient and the donor.