Diagnostic value of glomerular filtration rate, microalbuminuria, β2-microglobulin and cystatin C for renal function in patients with diabetic nephropathy

Objective 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. Methods 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. 99Tcm-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. Results 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 0.05), 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). Conclusions 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. Key words: Diabetic nephropathies; Glomerular filtration rate; Albumins; beta 2-Microglobulin; Cystatin C