| Objectives: To evaluate the accuracy of Cockcroft-Gault(C-G) and simplified MDRD equations in estimating the glomerular filtration rates (GFR) in Chinese diabetes mellitus patients. To investigate the value of urinary albumin creatinine ratio (ACR) and glomerular filtration rate (GFR) in the diagnosis of diabetic with chronic kidney disease, and the relationship between GFR and diabetes risk factors.Methods: 210 GFR measured by radiolabeled diethylenetriaminepentaacetic acid (99mTc-DTPA) was used as the reference standard. Serum creatinine and body weight were used to estimate GFR (eGFR) by C-G equation and simplified MDRD equation respectively. eGFRs were compared with measured GFR. The agreements between them were evaluated by kappa statistics. We analyzed the clinic characteristics in 294diabetes mellitus patients with normal ACR and low GFR. In the end, we compared the capability of diagnosis between ACR and the joint diagnosis in diabetes mellitus with the standard of serum creatinine.Results: Two hundred and ten diabetes mellitus patients aged (56.54±13.70)years were enrolled in this study. The body weight was(68.06±10.85)kg and the serum creatinine was(76.87±34.25)umol/L. The measured GFR was(85.18±24.96)ml·min-1·1.73m-2. The eGFR from C-G equation (eGFR1) was(97.04±37.15)ml·min-1·1.73m-2. The eGFR fron simplified MDRD equation (eGFR2) was(104.09±37.14)ml·min-1·1.73m-2. The median bias was-6.47 ml·min-1·1.73m-2 (P) between eGFR1 and measured GFR, and was -16.51 ml·min-1·1.73m-2 between eGFR2 and measured GFR. Pearson correlation analysis showed good correlation between measured GFR and eGFRs. For C-G equation the Kappa value was 0.554. For simplified MDRD equation the Kappa value was 0.646.Among the total 294 diabetes mellitus patients, there were 157 patients with normoalbuminuria, 91 patients with microalbuminuria and 46 patients with macroalbuminuria. There were 59 patients who had low GFR(GFR < 60 ml·min-1·1.73m-2). And the patients with normal albuminuria, microalbuminuria and macroalbuminuria who were appeared to decline in GFR were respectively 9.6% (15/157), 25.3% (23/91), 45.7% (21/46). Based on ACR alone, the sensitivity of diagnosis for diabetic kidney damage was 88.9% and the specificity was 59.3%.while based on GFR alone, the sensitivity and specificity were 80.6%, 88.8% respectively. However, with the combined ACR and GFR standard, the sensitivity and specificity of diagnosis for renal impairment in diabetes mellitus patients were 94.4% and 54.3% respectively, which had increased the diagnostic capacity of renal impairment in diabetic patients. Stepwise logistic regression analysis revealed that serum creatinine(OR=15.845,P < 0.001), age(OR=1.093,P < 0.001) were independently associated with renal impairment among the diabetes mellitus patients. BMI, blood urea nitrogen (BUN), urinary albumin excretion rate (UAER) is also associated with the decrease of GFR (P <0.05).Age (OR = 1.159) is the main factor in diabetic patients with normal ACR and low GFR (P = 0.016).Conclusions: Compared with the reference standard, both equations show a lower degree of accuracy. The simplified MDRD equation shows a little better than C-G equation in Chinese diabetes mellitus patients. More attention should be paid to set up an accurate GFR-estimating equation on the diabetes mellitus patients. Part of diabetic patients with normal ACR had occurred renal impairment, the evaluation with proteinuria alone for diabetic renal damage patients may resulted in missed diagnosis, Combination of ACR and GFR to diagnose diabetes patients could better evaluate the renal function. We suggest that the diabetic patients with normal ACR and GFR should be given a full attention.
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