Assessing suitability for renal donation: can equations predicting glomerular filtration rate substitute for a reference method in the Indian population?

Abstract

Background: Accurate measurement of donor renal function has important long-term implications for both the donor and recipient. As the use of recommended filtration markers is limited by cumbersome and costly techniques, renal function is typically estimated using 24-hour urinary creatinine clearance (urine-CrCl). Prediction equations used for rapid bedside estimation of glomerular filtration rate (GFR) are simple and overcome the inaccuracies of urinary collection and, if validated, can expedite the donor workup besides reducing the cost. We assessed the suitability of urine-CrCl and prediction equations for evaluating potential Indian renal donors.

Methods: 173 consecutive renal donors were enrolled. The predictive capabilities of the Cockcroft and Gault equation for creatinine clearance (CrCl) corrected for body surface area (CG-CrCl), CG-CrCl corrected for GFR (CG-GFR), MDRD-1, MDRD-2 and urine-CrCl were evaluated with 99mTc-diethylenetriaminepentaacetic acid (DTPA)-GFR as reference GFR.

Results: The study population had a mean age of 44.1 years with 74% being females. Mean DTPA-GFR was 83.85 ml/min/1.73 m2. The median percent absolute difference was most with urine-CrCl and least with CG-GFR (21.84 and 13.82). The Pearson's correlation varied from 0.08 to 0.26 (urine-CrCl and MDRD-1). The precision was most with MDRD-1 and least with urine-CrCl (0.07 and 0.01). The bias was least with CG-GFR and most with MDRD-2 (1.34 and 17.16). The number of subjects with predicted GFR values within 30% of DTPA was most with MDRD-1 (86%) and least with urine-CrCl (69%). The sensitivity for selecting a donor with a GFR of > or = 80/ml/min/1.73 m2 was the most with CG-GFR (65.7%), while specificity was maximum with MDRD-2 (90.1%).

Conclusion: Our results in potential Indian renal donors show that of all the prediction equations MDRD-1 is the most precise and accurate, while CG-GFR is the least biased. However, the poor correlation and level of error exhibited by these equations makes them suboptimal for donor evaluation.