Objective: To compare e-GFR estimated by creatinine or cystatin C based and combined creatinine and cystatin C based equations in type 2 diabetics in different stages of albuminuria.
Study Design: Comparative cross-sectional study.
Place and Duration of Study: Department of Chemical Pathology, Army Medical College Rawalpindi in
collaboration with endocrinology outpatient department Military Hospital Rawalpindi, from Nov 2015 to Nov
Material and Methods: A total of 119 type 2 diabetic subjects of either gender, aged 30- 60 years were enrolled in the study with duration of diabetes less than 15 years and were divided into further sub groups on the basis of degree of albuminuria determined by spot urine albumin to creatinine ratio (uACR). Fifty age matched disease free controls with no history of any systemic disease were also included in the study. Known patients of type 1 diabetes, chronic inflammatory disorders, uncontrolled hypertension, thyroid disease, chronic kidney disease, on lipid lowering drugs, steroids, ACE inhibitors and pregnant ladies were excluded from the study. Serum creatinine serum cystatin C were assessed on fully automated chemistry analyzer selectra. E-GFR was calculated by online GFR calculator by National Kidney Foundation. Comparison of means of e-GFR calculated by various equations was carried out by one way ANOVA and post-hoc Tukey tests. Degree of agreement between various equations for the estimation of GFR was assessed by kappa statistics. A p-value less than 0.05 were considered statistically significant.
Results: Mean e-GFR (ml/min/1.73m2) was lowest in cystatin C based CKD-EPI equation (89.56 ± 39.84) followed by combined cystatin C and creatinine based CKD-EPI (92.34 ± 37.88). Values of e-GFR by creatinine based CKD-EPI equation (95.84 ± 27.24), and by creatinine based MDRD equation (105.37 ± 64.98) were both higher. In creatinine based MDRD, equation normo albuminuria and micro albuminuria groups did not show statistically significant difference as compared to each other and control group. The mean value of e-GFR was found to be lowest in the normo albuminuric diabetics when estimated by cystatin C based CKD-EPI equation (88.82 ± 46.98) followed by combined creatinine and cystatin C based CKD-EPI equation (95.73 ± 42.96).
Conclusion: Cystatin C based CKD-EPI equation for e-GFR identifies more patients with glomerular dysfunction in normo-albuminuric stage of DKD as compared to cystatin C and creatinine based CKD-EPI and creatinine based MDRD equations. Therefore, e-GFR estimated by serum cystatin C based CKD-EPI formula is a better option for assessing the renal status in patients of early DKD.
Keywords : Cystatin C, Diabetic kidney disease, e-GFR.