Comparison of two prediction equations with radionuclide glomerular filtration rate: validation in routine use

Recent guidelines recommend automatic reporting of estimated glomerular filtration rate (eGFR) using the abbreviated Modification of Diet in Renal Disease (MDRD) equation with every request for plasma creatinine. We evaluated the performance of the MDRD and Cockcroft-Gault equations in routine use compared with a radionuclide GFR method.

Data collected on 601 patients aged 16-85 years who had undergone radionuclide GFR and eGFR was calculated using both equations for each patient. Calculations of bias, correlation coefficients and percentage estimates within 30% and 50% of radionuclide GFR were used in comparisons.

Overall, there was no significant difference in the performance between the two equations when compared with radionuclide GFR. When all creatinine results <60 micromol/L were adjusted to 60 micromol/L, and when creatinine results <60 micromol/L were excluded, MDRD performed better than the Cockcroft-Gault equation. MDRD was also superior for prediction of radionuclide GFR of <60 mL/min/1.73 m(2) (P=0.014).

The abbreviated MDRD formula for eGFR is superior to the Cockcroft-Gault equation for prediction of radionuclide GFR of <60 microL/min/1.73 m(2)and is more accurate when creatinine results <60 micromol/L are either corrected to 60 micromol/L or excluded from eGFR calculations.