Background
The accuracy of the measurement of renal function in potential living kidney donors (PLKD) is essential. Te direct measurement of glomerular fltration rate (mGFR) has been considered the “gold standard.” The estimated GFR (eGFR) with 24- hour urinary creatinine clearance (CrCl) is frequently used because of its availability. We aim to evaluate the correlation and agreement of eGFR using serum-based creatinine formulas (Cockcroft–Gault, MDRD, and CKD-EPI) and the eGFR based on 24- hour urinary CrCl to evaluate kidney function in PLKD.
Methods
We evaluated the kidney function in 799 PLKD using 24-hour urinary CrCl method and compared the correlation and agreement with the eGFR based on creatinine formulas (Cockcroft–Gault, MDRD, and CKD-EPI). We calculated the mean bias (diference), precision (SD of this diference), accuracy, and performed Bland–Altman plots.
Results
A total of 799 PLKD were analyzed. Te age of the PLKD ranged from 18 to 73 years. Weak to mild correlation was observed between 24-hour urinary CrCl and all formulas (ranged from 0.31 to 0.49). Te three equations underestimated the GFR. Using the Bland–Altman graphic, we observed that the CKD-EPI was the least scattered and most precise; however, mean bias and the interval range (limits of agreement) of all formulas were too big to assume equivalence between 24-hour urinary CrCl method and eGFR based on creatinine. Results of mean bias were similar when comparing the three equations in patients with CrCl GFR <60. However, the accuracy of all formulas was better for the female group and the youngest individuals (≤40 years old).
Conclusion
In this PLKD cohort, of all the three equations, the CKD-EPI was the least scattered and most precise. However, the correlation and the level of agreement between the three equations and 24-hour urinary CrCl were too low to assume the equivalence