A study on comparison of Tc-99m DTPA renal dynamic imaging with Mayo quadratic, Cockcroft-Gault, MDRD, and CKD-EPI formulas for estimation of glomerular filtration rate among South Indian live-related kidney donors

Introduction: Glomerular filtration rate (GFR) is calculated using various prediction equations. These equations are derived from the Western population, and extrapolating to our population subgroups may yield inaccurate results. Objectives: To study the correlation of measured GFR to estimated GFR using four different equations and to analyse how much proximity lies between the GFR calculated by above formulas correlates with DTPA renal scan among South Indian renal donors. Patients and Methods: An observational study was conducted among prospective renal donors undergoing evaluation. Donors underwent a DTPA scan as per protocol. Downloadable calculators calculated the glomerular filtration rate. Results that were descriptive were presented as mean and standard deviation. Correlation and comparisons were made by calculating Pearson’s correlation coefficient and student’s t test respectively. Results: A total of 151 patients were included; 24.5% were males and 75.5% were females. The majority of donors (37.09%) were in the 45-54 years age group. The mean of measured GFR by DTPA was 105.64 mL/min/1.73 m2 whereas estimated GFR was 100.95, 102.34, 109.35, 97.44 mL/min/1.73 m2 in MDRD, CKD-EPI, Mayo, and Cockcroft Gault (CG) formulae respectively with a maximum mean difference for CG of 8.2. Weighted kappa agreement between measured and estimated GFR shows 82.96% agreement with CKD-EPI compared to 78.09% agreement with the MDRD formula. Overall, CKD-EPI performed better in GFR estimation in our study subjects. Conclusion: We found that the CKD-EPI formula performed better in precision, correlation, and accuracy compared to other formulae in GFR estimation among healthy South Indian renal donors. Therefore, the CKD-EPI formula is best suited to pick-up subnormal GFR in clinical practice, as well as in epidemiological studies among the South Asian population.