Abstract:

Objective  To establish the glomerular filtration rate (GFR) estimation equation based on cystatin C (Cys C) for type 2 diabetes mellitus patients and assess the applicability for predicting the renal function. Methods  Clinical data of 856 type 2 diabetes mellitus patients were collected and levels of serum creatinine (SCr), Cys C, and plasma glycosylated hemoglobin concentration (HbA1c) were detected. The 99mTc-diethylenetriamine pentaacetic acid-deoxyglucose (99mTc-DTPA) renal dynamic imaging was conducted to obtain the isotopic GFR (iGFR), which was used as the reference of GFR. Among 856 patients, 660 of them were randomly selected for establishing the estimation equation and other 196 patients belonged to the validation group. The GFR values (eGFR) estimated by self-established equation, modification of diet in renal disease (MDRD), chronic kidney disease epidemiology collaboration Cys C equation, and Cys C/SCr combined equation (CKD-EPICys C, CKD-EPISCr/Cys C) were compared by statistical methods, including paired t test, Bland and Altman procedures, χ2 test, Spearman correlation analysis, and receiver operating characteristic (ROC) curves. Results  The self-established equation based on Cys C for type 2 diabetes mellitus patients was 87.2×Cys C-1-4.6. For the validation group, compared with iGFR, the bias, consistency, and coincidence rate of eGFR estimated by the self-established equation were better than those of eGFRs estimated by MDRD and CKD-EPISCr/Cys C equations, and the bias and coincidence rate of eGFR estimated by the self-established equation were better than those of eGFR estimated by CKD-EPICys C equation. The percentages of correct staging of chronic kidney disease for diabetes mellitus patients with mildly to moderately decreased renal function by the self-established equation and CKD-EPICys C equation were significantly higher than those by MDRD and CKD-EPISCr/Cys C functions. The differences of bias and coincidence rate between the self-established and CKD-EPICys C equations among patients with different blood glucose controlled levels were not statistically significant (P>0.05). Conclusion  The self-established Cys C equation is applicable for estimating the GFR of diabetes mellitus patients with different renal function levels and different blood glucose controlled levels.

Key words: type 2 diabetes mellitus, cystatin C, glomerular filtration rate, estimation equation