Clinnical Value Of Serum Cystatin C To The Diagnosis Of Kidney Damage

Objective: CKD is an important public health problem and estimation of the glomerular filtration rate (GFR) is essential for the evaluation of patients with CKD. The current Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines stratify CKD into five stages, also on the basis of GFR estimations [1]. Mild reduction in GFR was defined as CKD only in the presence of kidney damage (stage 2 of CKD; GFR 89-60 ml/min/1.73 m2). Moderate (stage 3 of CKD; GFR 59-30 ml/min/1.73 m2) to severe (stage 4 of CKD; GFR 29-15 ml/min/1.73 m2) reduction in GFR and kidney failure (stage 5 of CKD; GFR<15 ml/min/1.73 m2) were defined as CKD, irrespective of the presence of kidney damage. Recently, serum cystatin C was proposed as a new endogenous marker of GFR and in our study its accuracy was compared with that of other markers of GFR.Methods: In this study, 132 patients with CKD stages 2-3(GFR30-89ml/min/1.73m2), Serum Cys C,β2-Microglobulin (β2-MG),Creatinine, Creatinine clearance rate (CCr),blood urea nitrogen (BUN),UA acid(UA) and retinol-binding protein (RBP) were assayed from 66 case with hypertention or diabetic an other diseasesand compared with those of 50 healthy persons as control group. We retrospectively analyzed correlation, bias, precision and accuracy of two Cys C-based formulae (Larsson and Hoek) for GFR estimation in comparison with creatinine-based Cockroft &Gault equations. Plasma cystatin C was measured by an automated particle-enhanced immunoturbidimetric method.Results: Serum Cys C,β2-MG of patients increased significantly but GFR decreased. When the kedney is mild dysfunction,the Cys C decreased, however BUN and UA do not increase. The area under the curve for cystatin C (0.999) was significantly larger than that forβ2-MG (0.998) and creatinine (0.933) but obviously large than that for BUN (0.787) and UA (0.687). GFR negatively correlated with Cys C,β2-MG,BUN,SCr and UA. The sensitivity of Cys C andβ2-MG was better than those of others.Conclusion: Our results indicate that serum Cys C may be an ideal marker of GFR in patients with mildly to moderately impaired kidney function and has a higher diagnostic accuracy than serum creatinine and other markers Cys C assay be used as a normol method for the purpose of diagnosising the mild to moderate impairment of kidney function...