Hojs R, Bevc S, Ekart R, Gorenjak M, Puklavec L
Department of Nephrology, Clinic of Internal Medicine, University Medical Center Maribor, Slovenia.
Clin Nephrol. 2008 Jul;70(1):10-7. doi: 10.5414/cnp70010.
Estimation of the glomerular filtration rate (GFR) is essential for the evaluation of patients with chronic kidney disease (CKD). The Cockcroft-Gault (CG) and modification of diet in renal disease (MDRD) formulas are serum creatinine-based equations, and the most widely used tests for renal function. Recently, serum cystatin C-based equations were proposed as markers for estimation of GFR. The present study compares our serum cystatin C-based equation (cystatin C formula) and serum creatinine-based equations for a large group of patients with CKD. In this study, 592 adult patients with CKD were enrolled. In each patient, serum creatinine was determined and creatinine clearance was calculated using the CG and MDRD formulas. The serum cystatin C was determined by an immunonephelometric method and our own cystatin C formula (GFR = 90.63 x cystatin C-1.192) for estimation of GFR was developed. GFR was measured using 51CrEDTA clearance, and the correlation, accuracy, bias and precision were determined. Ability to correctly estimate the patient's GFR with different equations compared to gold standard below and above 60 ml/min/1.73 m2; was analyzed. The mean 51CrEDTA clearance was 47 ml/min/1.73 m2, the mean serum creatinine was 269 micromol/l and the mean serum cystatin C was 2.68 mg/l. Statistically significant correlation between 51CrEDTA clearance with the CG (r = 0.861) and MDRD (r = 0.909) formulas and the cystatin C formula (r = 0.899) was found. The receiver operating characteristic (ROC) curve analysis (cut-off for GFR 60 ml/min/1.73 m2) showed that the cystatin C formula had a significantly higher diagnostic accuracy than the CG formula (p < 0.003). All equations underestimated the measured GFR and lacked precision. Analysis of ability to correctly predict the patient's GFR below or above 60/ml/min/1.73 m2 showed a higher prediction for the cystatin C formula than the MDRD formula (91.6 versus 84.1%, p < 0.0005) and a higher prediction trend than the CG formula (91.6 versus 88.3%, p = 0.078). Our results indicate that serum cystatin C-based equation is a reliable marker of GFR with a very high diagnostic accuracy and ability to predict patients with CKD and GFR under 60/ml/min/1.73 m2.
估算肾小球滤过率（GFR）对于评估慢性肾脏病（CKD）患者至关重要。Cockcroft-Gault（CG）公式和肾脏病饮食改良（MDRD）公式是以血清肌酐为基础的方程，是目前应用最广泛的肾功能检测方法。最近，基于血清胱抑素C的方程被提议作为估算GFR的指标。本研究比较了我们基于血清胱抑素C的方程（胱抑素C公式）和基于血清肌酐的方程在一大组CKD患者中的表现。本研究纳入了592例成年CKD患者。测定每位患者的血清肌酐，并使用CG公式和MDRD公式计算肌酐清除率。采用免疫比浊法测定血清胱抑素C，并建立了我们自己的用于估算GFR的胱抑素C公式（GFR = 90.63×胱抑素C-1.192）。采用51CrEDTA清除率测定GFR，并确定相关性、准确性、偏差和精密度。分析了与低于和高于60 ml/min/1.73 m2的金标准相比，不同方程正确估算患者GFR的能力。51CrEDTA清除率的平均值为47 ml/min/1.73 m2，血清肌酐的平均值为269 μmol/l，血清胱抑素C的平均值为2.68 mg/l。发现51CrEDTA清除率与CG公式（r = 0.861）、MDRD公式（r = 0.909）以及胱抑素C公式（r = 0.899）之间存在统计学显著相关性。受试者工作特征（ROC）曲线分析（GFR的截断值为60 ml/min/1.73 m2）显示胱抑素C公式的诊断准确性显著高于CG公式（p < 0.003）。所有方程均低估了实测GFR且缺乏精密度。分析低于或高于60/ml/min/1.73 m2时正确预测患者GFR的能力，结果显示胱抑素C公式的预测率高于MDRD公式（91.6%对84.1%，p < 0.0005），且预测趋势高于CG公式（91.6%对88.3%，p = 0.078）。我们的结果表明，基于血清胱抑素C的方程是GFR的可靠指标，具有很高的诊断准确性以及预测CKD患者和GFR低于60/ml/min/1.73 m2患者的能力。
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