Significant differences when using MDRD for GFR estimation compared to radionuclide measured clearance.

Area of Science:

• Nephrology
• Radiology
• Medical Imaging

Background:

• Accurate assessment of renal function is crucial before administering contrast agents in radiology.
• Estimated Glomerular Filtration Rate (eGFR) is commonly used, but its accuracy compared to radionuclide GFR (rGFR) requires evaluation.

Purpose of the Study:

• To compare eGFR, calculated using the Modification of Diet in Renal Disease equation, with rGFR in a radiology setting.
• To assess the reliability of eGFR for evaluating renal function prior to contrast administration.

Main Methods:

• Retrospective analysis of 516 rGFR studies from a mixed referral population.
• Calculation of eGFR using the Modification of Diet in Renal Disease equation.
• Statistical analysis including regression and Bland-Altman methods to compare eGFR and rGFR.

Main Results:

• A significant correlation (R² = 0.62, p < 0.0001) was found between eGFR and rGFR, but with significant median differences (p < 0.0001).
• eGFR consistently overestimated rGFR, with a mean bias of 10.8 ml/min/1.73 m² across all ranges.
• Lower eGFR values showed notable overestimation, impacting the classification of renal insufficiency.

Conclusions:

• There is a significant bias where eGFR overestimates rGFR in radiology patients.
• Awareness of this eGFR/rGFR bias is essential for accurately assessing risks of contrast-induced nephrotoxicity and Nephrogenic Systemic Fibrosis.