To investigate the clinical value of GFR, microalbuminuria (mAlb), serum β₂-microglobulin (MG) and cystatin C (CysC) for the evaluation of renal function in patients with DN.

A total of 150 patients with type 2 DM diagnosed by WHO standard (1999) from December 2012 to December 2015 were retrospectively analyzed. Thirty-three kidney transplantation donors during the same time were chosen as the control group. The urine mAlb, Cr, albumin/Cr ratio(ACR) and SCr, serum β₂-MG, CysC, urea, uric acid(UA), fasting blood glucose (FBG), hemoglobin A lc (HbA1c) and C-reactive protein (CRP) were measured. ⁹⁹Tc^m-DTPA renal dynamic imaging was performed. The Gates method was used to calculate GFR, and the modification of diet in renal disease (MDRD) method was used to calculate the estimated GFR (eGFR). The relative equation between GFR and eGFR was studied. The clinical stages of renal function in type 2 DM patients were evaluated by Mogenesen standard method. Two-sample t test was used for data analysis. ROC curve analysis was performed to study the diagnostic value of GFR in DN.

The patients were divided into merely type 2 DM group, early stage DN (Ⅰ, Ⅱ, Ⅲ), and clinical DN(Ⅳ) groups by Mogenesen standard method. GFR and eGFR in the DNⅠstage were higher than those of the merely type 2 DM group (t values: -7.502, -3.629, both P<0.01), and GFR and eGFR decreased with the increased stage of DN. However, serum UA, CRP, FBG and HbA1c, SCr, urea, β₂-MG, CysC, mAlb and ACR increased when the stage of DN was higher. GFR and eGFR showed a linear correlation, with the regression equation of y=0.957x+ 6.823. AUC of ROC in patients with DN Ⅰ was 0.989. With the cutoff value of 125.09 ml/min, the sensitivity and specificity was 96.2%(25/26) and 98.4%(122/124) respectively in diagnosis of DNⅠ. Between high UA and normal UA groups, FBG and HbA1c were not significantly different (t values: -1.010, -1.034, both P>0.05), but the renal function indicators were different (t values: -5.090-2.209, all P<0.01). Compared with the normal CRP group, the FBG, HbA1c and renal function indicators were statistically different in high CRP group (t values: -6.114-7.386, all P<0.01).

GFR and eGFR show a linear relationship in type 2 DM. GFR is a sensitive, specific diagnostic index in DN Ⅰ period. β₂-MG, CysC, mAlb and ACR are conducive to the early diagnosis of DN. High UA is an independent risk factor for the onset of DN, and high CRP is an inflammatory damage factor in DN.

Diabetic nephropathies; Glomerular filtration rate; Albumins; beta 2-Microglobulin; Cystatin C