Published in:
01-10-2011 | Physics
Significant differences when using MDRD for GFR estimation compared to radionuclide measured clearance
Published in: European Radiology | Issue 10/2011
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Objectives
To evaluate Estimated Glomerular Filtration Rate (eGFR), using the Modification of Diet in Renal Disease equation, and compare with radionuclide GFR (rGFR) in a Radiology setting to assess renal function prior to contrast administration.
Methods
Five hundred and sixteen retrospective rGFR studies from a mixed referral population were selected and the eGFR calculated. Regression and Bland-Altman analysis was performed. The percentage of rGFR and eGFR studies below 30 ml/min/1.73 m2 and 60 ml/min/1.73 m2 were calculated; these are important thresholds for classifying renal insufficiency.
Results
A significant correlation between eGFR and rGFR (R2 = 0.62, p < 0.0001) and significant differences in the medians (p < 0.0001) were found. eGFR overestimated rGFR with a bias (mean difference) of 10.8 ml/min/1.73 m2 over the whole range of rGFR. Studies with an rGFR of under 30 ml/min/1.73 m2 had a mean bias of 4.6 ml/min/1.73 m2 (difference range −5.9 to 26.3 ml/min/1.73 m2). The bias over the range 30 to 60 ml/min/1.73 m2 was 13.2 ml/min/1.73 m2 (difference range −16.8 to 88.3 ml/min/1.73 m2). In 25.4% of studies, eGFR was less than 60 ml/min/1.73 m2 compared with 40.5% of rGFR studies.
Conclusions
Awareness of the bias between eGFR and rGFR is important when assessing Radiology patients for risks of nephrotoxicity and Nephrogenic Systemic Fibrosis from contrast medium.