Modification of Diet in Renal Disease equation underestimates glomerular filtration rate in Egyptian kidney donors.

Objectives: Inulin clearance and radioisotope studies are the most accurate means of measuring glomerular filtration rates (GFRs). The Kidney Disease Outcomes Quality Initiative guidelines recommend estimating GFRs with the Modification of Diet in Renal Disease (MDRD) or the Cockcroft- Gault equation. We examined the accuracy of the MDRD equation and creatinine clearance based on 24-hour urine collection to predict GFRs in a group of healthy donors.

Materials And Methods: We examined the medical records of 100 kidney donors who had undergone 99mTc-diethylenetriamine-pentaacetic acid (DTPA) renal clearance and creatinine clearance measurements at the transplant outpatient clinic of Cairo University Hospital in Cairo, Egypt, between June 2002 and July 2006. GFR was predicted with the abbreviated MDRD formula. We examined significant differences, potential correlations, and agreements between GFR as predicted and as measured.

Results: The mean eGFRMDRD was 8.16% lower than the 99mTc-DTPA GFR (116.11 -/+ 25.44mL/min/1.73m2 vs 126.32 -/+ 24.21 mL/min/1.73 m2; difference range, -84 to +61 mL/min/1.73 m2; P = .002). Creatinine clearance was 13.14% higher than the 99mTc-DTPA GFR (142.90 -/+ 27.51 mL/min/1.73 m2; difference range, +65 to -60 mL/min/1.73 m2; P < .001). A significant positive correlation was observed when creatinine clearance and 99mTc-DTPA-measured GFR were compared (R=0.451; P = .000). No significant correlation was noted between eGFRMDRD and 99mTc-DTPA-measured GFRs (R=0.126; P = .211). A Bland-Altman analysis showed poor agreement between GFRMDRD and creatinine clearance on the one hand and measured GFR on the other.

Conclusions: Neither the MDRD equation nor creatinine clearance is accurate in predicting GFRs in healthy donors.