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OBJECTIVE—About 20% of diabetic patients with chronic kidney disease (CKD) detected from the new American Diabetes Association recommendations (albumin excretion rate >30 mg/24 h or estimated glomerular filtration rate [GFR] RESEARCH DESIGN AND METHODS—A total of 89 patients with diabetes and a modification of diet in renal disease (MDRD) estimated GFR (e-GFR) RESULTS—The mean MDRD e-GFR (41.3 ± 13.1 ml/min per 1.73 m2) did not significantly differ from the i-GFR (45.6 ± 29.7). Of the subjects, 15 (17%) were normoalbuminuric. Their i-GFR did not differ from the albuminuric rate and from their MDRD e-GFR, although their serum creatinine was lower (122 ± 27 vs. 160 ± 71 μmol/l, P < 0.05): 71% would not have been detected by measuring serum creatinine (sCr) alone. They were less affected by diabetic retinopathy, and their HDL cholesterol and hemoglobin were higher (P < 0.05 vs. albuminuric). None of the CKD normoalbuminuric subjects started dialysis (microalbuminuric: 2/36, macroalbuminuric: 10/38) or died (microalbuminuric: 3/36, macroalbuminuric: 7/38) during the follow-up period (log-rank test: P < 0.005 for death or dialysis), and their albumin excretion rate and sCr values were stable after 38 months, whereas the AER increased in the microalbuminuric patients (P < 0.05), and the sCr increased in the macroalbuminuric patients (P < 0.01). CONCLUSIONS—Although their sCr is usually normal, most of the normoalbuminuric diabetic subjects with CKD according to an MDRD e-GFR below 60 ml/min per 1.73 m2 do really have a GFR below 60 ml/min per 1.73 m2. However, as expected, because of normoalbuminuria and other favorable characteristics, their risk for CKD progression or death is lower.

OBJECTIVE—The Cockcroft-Gault and Modification of Diet in Renal Disease (MDRD) equations poorly predict glomerular filtration rate (GFR) decline in diabetic patients. We sought to discover whether new equations based on serum creatinine (the Mayo Clinic Quadratic [MCQ] or reexpressed MDRD equations) or four cystatin C–based equations (glomerular filtration rate estimated via cystatin formula [Cys-eGFR]) were less biased and better predicted GFR changes. RESEARCH DESIGN AND METHODS—In 124 diabetic patients with a large range of isotopic GFR (iGFR) (56.1 ± 35.3 ml/min per 1.73 m2 [range 5–164]), we compared the performances of the equations before and after categorization in GFR tertiles. A total of 20 patients had a second determination 2 years later. RESULTS—The Cockcroft-Gault equation was the least precise. The MDRD equation was the most precise but the most biased according to the Bland-Altman procedure. By contrast with the MDRD and, to a lesser extent, the MCQ, three of the four Cys-eGFRs were not biased. All equations overestimated the low GFRs, whereas only the MDRD and Rule's Cys-eGFR equations underestimated the high GFRs. For the subjects studied twice, iGFR changed by −8.5 ± 17.9 ml/min per 1.73 m2. GFR changes estimated by the Cockcroft-Gault (−4.5 ± 6.8) and MDRD (−5.7 ± 6.2) equations did not correlate with the isotopic changes, whereas new equation-predicted changes did: MCQ: −8.7 ± 9.4 (r = 0.44, P < 0.05) and all four Cys-eGFRs: −6.2 ± 7.4 to −7.3 ± 8.4 (r = 0.60 to 0.62, all P < 0.005), such as 100/cystatin-C (r = 0.61, P < 0.005). CONCLUSIONS—The new predictive equations better estimate GFR than the Cockcroft-Gault equation. Although the MDRD equation remains the most accurate, it poorly predicts GFR decline, as it overestimates low and underestimates high GFRs. This bias is lesser with the MCQ and Cys-eGFR equations, so they better predict GFR changes.

About 20% of diabetic patients with chronic kidney disease (CKD) detected from the new American Diabetes Association recommendations (albumin excretion rate30 mg/24 h or estimated glomerular filtration rate [GFR]60 ml/min per 1.73 m2) may be normoalbuminuric. Do the characteristics and outcome differ for subjects with and without albuminuria?A total of 89 patients with diabetes and a modification of diet in renal disease (MDRD) estimated GFR (e-GFR)60 ml/min per 1.73 m2 underwent a 51Cr-EDTA B-isotopic GFR determination and were followed up for 38 +/- 11 months.The mean MDRD e-GFR (41.3 +/- 13.1 ml/min per 1.73 m2) did not significantly differ from the i-GFR (45.6 +/- 29.7). Of the subjects, 15 (17%) were normoalbuminuric. Their i-GFR did not differ from the albuminuric rate and from their MDRD e-GFR, although their serum creatinine was lower (122 +/- 27 vs. 160 +/- 71 micromol/l, P0.05): 71% would not have been detected by measuring serum creatinine (sCr) alone. They were less affected by diabetic retinopathy, and their HDL cholesterol and hemoglobin were higher (P0.05 vs. albuminuric). None of the CKD normoalbuminuric subjects started dialysis (microalbuminuric: 2/36, macroalbuminuric: 10/38) or died (microalbuminuric: 3/36, macroalbuminuric: 7/38) during the follow-up period (log-rank test: P0.005 for death or dialysis), and their albumin excretion rate and sCr values were stable after 38 months, whereas the AER increased in the microalbuminuric patients (P0.05), and the sCr increased in the macroalbuminuric patients (P0.01).Although their sCr is usually normal, most of the normoalbuminuric diabetic subjects with CKD according to an MDRD e-GFR below 60 ml/min per 1.73 m2 do really have a GFR below 60 ml/min per 1.73 m2. However, as expected, because of normoalbuminuria and other favorable characteristics, their risk for CKD progression or death is lower.

OBJECTIVE—Hyperglycemia increases glomerular filtration rate (GFR), but the influence of HbA1c (A1C) on GFR and GFR’s prediction by recommended equations remains to be determined. RESEARCH DESIGN AND METHODS—In 193 diabetic patients, we searched for an association between A1C and isotopically measured GFR (51Cr-EDTA) and their predictions by the Cockcroft and Gault formula (CG) and the modification of diet in renal disease (MDRD) equation. Their accuracy for the diagnosis of moderate (GFR RESULTS—The mean GFR was 57.0 ± 34.8 ml/min per 1.73 m2 and was well correlated with both estimations (CG r = 0.75, MDRD r = 0.83; P < 0.05). The areas under the ROC curves were higher with the MDRD (P < 0.05). A1C was correlated (P < 0.001) with the GFR (r = 0.29), MDRD (r = 0.38), CG (r = 0.26), and the absolute differences between the GFR and their CG but not MDRD estimations (r = 0.17, P < 0.05). Each +1% A1C was associated with +6.0 ml/min per 1.73 m2 GFR (CG +5.6, MDRD +5.3). After separating well-controlled (n = 88, A1C 7.0 ± 0.7%) and poorly controlled (n = 105, 9.6 ± 1.3%) patients, the diagnostic accuracies were better (P < 0.05) for the MDRD, except for the diagnosis of moderate renal failure in well-controlled patients (NS). CONCLUSIONS—GFR and its estimations correlate with A1C. Although the relations between GFR and its estimations were not affected by the degree of glucose control, the precision and diagnostic accuracy of the CG formula were diminished for A1C >8%. The MDRD equation was more accurate and robust in diabetic patients with impaired renal function.

The Cockcroft-Gault formula is recommended for the evaluation of renal function in diabetic patients. The more recent Modification of Diet in Renal Disease (MDRD) study equation seems more accurate, but it has not been validated in diabetic patients. This study compares the two methods.In 160 diabetic patients, we compared the Cockcroft-Gault formula and MDRD equation estimations to glomerular filtration rates (GFRs) measured by an isotopic method ((51)Cr-EDTA) by correlation studies and a Bland-Altman procedure. Their accuracy for the diagnosis of moderately (GFR60 ml . min(-1) . 1.73 m(-2)) or severely (GFR30 ml . min(-1) . 1.73 m(-2)) impaired renal function were compared with receiver operating characteristic (ROC) curves.Both the Cockcroft-Gault formula (r = 0.74; P0.0001) and MDRD equation (r = 0.81; P0.0001) were well correlated with isotopic GFR. The Bland-Altman procedure revealed a bias for the MDRD equation, which was not the case for the Cockcroft-Gault formula. Analysis of ROC curves showed that the MDRD equation had a better maximal accuracy for the diagnosis of moderate (areas under the curve [AUCs] 0.868 for the Cockcroft-Gault formula and 0.927 for the MDRD equation; P = 0.012) and severe renal failure (AUC 0.883 for the Cockcroft-Gault formula and 0.962 for the MDRD equation; P = 0.0001). In the 87 patients with renal insufficiency, the MDRD equation estimation was better correlated with isotopic GFR (Cockcroft-Gault formula r = 0.57; the MDRD equation r = 0.78; P0.01), and it was not biased as evaluated by the Bland-Altman procedure.Although both equations have imperfections, the MDRD equation is more accurate for the diagnosis and stratification of renal failure in diabetic patients.