A Comparison of Glomerular Filtration Rate by Creatinine Based Equations and DTPA-Renogram in Healthy Adult Kidney Donors

Abstract

Introduction: Accurate determination of donor kidney function has important long-term implications for both donor health and recipient outcome. Many centers use 24 hour urinary creatinine clearance or creatinine-based GFR estimations to assess kidney function but their performance when compared with GFR measurements by isotope clearance remains inconclusive. We assessed the performance of creatinine based equations against DTPA GFR for evaluating Nepalese kidney donors.

Methods: All kidney donors who had undergone both DTPA GFR estimation and 24 hour urine CrCl were included. The performance of the urine-CrCl, CG-CrCl, modified MDRD GFR against DTPA GFR was evaluated by analyzing global bias, precision (R2),Pearson correlation and accuracy percentage within 30% and 15%. The sensitivity and specificity of each predictive equation in selecting donor with GFR of ≥80 mL/min/1.73 m2 was also calculated.

Results: Of 51 donors analysed, only 18 (35.29%) were male. The mean measured GFR was 102.752±16.71 mL/min/1.73 m2. Of all prediction equations, urine-CrCL has most precision (R2=0.207) with the highest pearson correlation (0.455) and highest accuracy percentage within 30% and 15%. However, predictive performance was poor for all the equations. The urine CrCl had highest sensitivity of 100% for detecting donor with measured GFR>80 mL/min/1.73 m2 with positive predictive value of 92.1%.

Conclusions: The performance of all equations was disappointing and even the best performing equation urine-CrCl was suboptimal for donor selection. So considering the potential risk of living kidney donation, other more accurate methods of GFR estimation should be used.
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Keywords: Cockcroft-Gault equation; creatinine clearance; glomerular filtration rate; modification of diet in enal disease formula; 99mTc-Diethylene-Triamine Pentaacetic Acid.