Comparison of the Mayo Clinic Quadratic Equation with the Modification of Diet in Renal Disease equation and radionuclide glomerular filtration rate in a clinical setting

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. The Mayo Clinic Quadratic Equation (MCQE) has been put forwards as a potentially more accurate alternative. We therefore evaluated its accuracy compared with radionuclide GFR in a clinical setting. Data were collected on 601 patients aged 16-85 years who had undergone radionuclide GFR, and eGFR was calculated using MCQE and MDRD. Calculations of bias, correlation coefficients and percentage estimates within 30% and 50% of radionuclide GFR were used in comparisons. The MCQE had a significant positive bias in the overall population but no significant bias in individuals with normal renal function defined as measured GFR > 90 mL/min per 1.73 m(2). There was no significant difference in the performance of MCQE and MDRD eGFR in patients with measured GFR > 90 mL/min per 1.73 m(2). However, in the overall group and in subjects with radionuclide GFR < 90 mL/min per 1.73 m(2), the accuracy of MDRD eGFR with respect to the proportion of patients within 30% and 50% of radionuclide GFR was better than MCQE. MCQE compared moderately well with radionuclide GFR, although its overall bias and accuracy were inferior when compared with the MDRD equation in a clinical setting.