DOI: 10.2337/dc05-2201 © 2006 by the American Diabetes Association
Monitoring Kidney Function in Type 2 Diabetic Patients With Incipient and Overt Diabetic Nephropathy
1 Steno Diabetes Center, Gentofte, Denmark Address correspondence and reprint requests to Peter Rossing, MD, DMSC, Niels Steensens Vej 2, DK 2820, Gentofte, Denmark. E-mail: pro{at}steno.dk OBJECTIVEThe purpose of this study was to assess agreement between glomerular filtration rate (GFR) and the decline in GFR estimated with the Modification of Diet in Renal Disease (MDRD) Study Group equation or the Cockcroft-Gault formula and measured by the plasma clearance of 51Cr-EDTA. RESEARCH DESIGN AND METHODSWe followed a cohort of 156 microalbuminuric type 2 diabetic patients for 8 years with four measurements of GFR and another cohort of 227 type 2 diabetic patients with overt diabetic nephropathy for 6.5 (range 317) years with seven (322) measurements of GFR. RESULTSFor patients with microalbuminuria, mean ± SD baseline GFR was 117 ± 24 measured, 92 ± 20 estimated (MDRD equation), or 103 ± 24 ml · min1 per 1.73 m2 estimated (Cockcroft-Gault formula) (both P < 0.001); 95% limits of agreement were 66.1 to 20.3 (MDRD equation) and 58.7 to 30.7 (Cockcroft-Gault formula). The rate of decline in GFR was 4.1 ± 4.2 measured, 2.9 ± 2.8 estimated (MDRD equation), or 3.4 ± 3.2 ml · min1 per 1.73 m2 estimated (Cockcroft-Gault formula) (both P < 0.001). For patients with overt nephropathy, baseline GFR was 84 ± 30 measured, 73 ± 24 estimated (MDRD equation), or 81 ± 28 ml · min1 per 1.73 m2 estimated (Cockcroft-Gault formula) (both P < 0.001) with 95% limits of agreement 47 to 25 (MDRD equation) and 39 to 33 (Cockcroft-Gault formula). The rate of decline in GFR was 5.2 ± 4.1 measured, 4.2 ± 3.8 estimated (MDRD equation), and 4.6 ± 4.1 ml · min1 per 1.73 m2 estimated (Cockcroft-Gault formula) (both P < 0.001). CONCLUSIONSParticularly in microalbuminuric (hyperfiltering) patients, GFR is significantly underestimated with wide limits of agreement by the MDRD equation as well as by the Cockcroft-Gault formula. The rate of decline in GFR is also significantly underestimated with both equations. This makes GFR estimations based upon these equations unacceptable for monitoring kidney function in type 2 diabetic patients with incipient and overt diabetic nephropathy.
Abbreviations: BSA, body surface area GFR, glomerular filtration rate MDRD, Modification of Diet in Renal Disease
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