Evaluation of Glomerular Filtration Rate by Prediction Equation in the Elderly

Lee, Yong Su; Lee, Kyu Beck; Lhee, Hyun Young; Kim, Hyang; Ryu, Seung Ho; Bark, Jung Mi

Abstract

BACKGROUND: The glomerular filtration rate (GFR) is considered the best overall index for the level of renal function and is estimated commonly by the creatinine-based, Cockcroft-Gault (CG) equation or the Modification of Diet Disease Study (MDRD) equation indirectly. Recently, cystatin C has been reported as a new endogenous marker of GFR. To predict the decrease of renal function in the elderly, we measured standard GFR (EDTA-GFR) by (51)Cr- EDTA and attempted to compare the result with CG, MDRD, and cystatin C equation for accuracy.
METHODS
Sixty-three elderly persons (28 men, 35 women:mean age 70, range 65-78) who underwent health screening, were measured for plasma creatinine, cystatin C and EDTA-GFR.
RESULTS
The CG and MDRD equations performed better than the cystatin C equation with an accuracy of within 30% (68 and 67%, respectively, versus 37%) and 50% (98 and 94%, respectively, versus 72%) of EDTA-GFR. The coefficient of determination (R2) of each estimated equation was 0.08 (p=0.03) in CG, 0.06 (p=0.04) in MDRD, and 0.07 (p=0.04) in cystatin C equation. Analysis of ROC curves with EDTA-GFR 60 mL/min/1.73m2 showed that each estimated equation was inadequate for the diagnosis of chronic kidney disease (sensitivity and specificity, 73% and 65% in CG, and 68% and 65% in MDRD, respectively).
CONCLUSION
In the elderly, CG or MDRD equation was more accurate than cystatin C equation. Nevertheless, problems remain in the assessment of GFR using these equations and caution is particularly necessary in the diagnosis of chronic kidney disease with calculated estimates of GFR<60 mL/ min/1.73m2 in the elderly.