Mussap M, Ruzzante N, Varagnolo M, Plebani M
Department of Laboratory Medicine, University-Hospital of Padova, Italy.
Clin Chem Lab Med. 1998 Nov;36(11):859-65. doi: 10.1515/CCLM.1998.151.
Human cystatin C is a low molecular mass protein of 13359 Dalton recently proposed as a new very sensitive marker of changes in glomerular filtration rate. Serum cystatin C concentration correlates negatively with glomerular filtration rate as well as or better than creatinine. We evaluated a recently introduced automated nephelometric immunoassay for cystatin C in serum or EDTA-plasma samples on the Behring Nephelometer System. The assay consists of incubating the 100-fold diluted sample for 6 minutes with latex particles covalently coated with anti-human cystatin C antibodies, and then quantifying the change of light-scatter produced. Method reproducibility is satisfactory, the intra- and inter-assay coefficients of variation ranging from 1.58% to 3.77% and from 5.6% to 11.47% respectively. Rheumatoid factor (< or = 1116 IU/ml), bilirubin (< or = 418 micrommol/l), triglycerides (10.47 mmol/), and haemoglobin (12 g/l) do not significantly interfere in the assay. No significant difference was found in cystatin C concentration between serum and EDTA-plasma samples. Cystatin C is stable in serum samples stored under different conditions up to one month. This method correlates well (mean difference=-0.536+/-0.307 mg/l) with another commercially available particle-enhanced turbidimetric immunoassay. Cystatin C offers better clinical sensitivity than creatinine for discriminating patients with normal renal function and those with mild-to-moderate reduction in renal function. This method is suitable for routine cystatin C measurement, including emergencies.
人胱抑素C是一种分子量为13359道尔顿的低分子量蛋白质，最近被提议作为肾小球滤过率变化的一种新的非常敏感的标志物。血清胱抑素C浓度与肾小球滤过率呈负相关，其相关性与肌酐相当或优于肌酐。我们在贝林散射比浊仪系统上评估了一种最近推出的用于血清或乙二胺四乙酸（EDTA）血浆样本中胱抑素C的自动散射比浊免疫测定法。该测定法包括将100倍稀释的样本与共价包被抗人胱抑素C抗体的乳胶颗粒孵育6分钟，然后定量所产生的光散射变化。方法的重现性令人满意，批内和批间变异系数分别为1.58%至3.77%和5.6%至11.47%。类风湿因子（≤1116 IU/ml）、胆红素（≤418 μmol/l）、甘油三酯（10.47 mmol/l）和血红蛋白（12 g/l）在测定中无显著干扰。血清和EDTA血浆样本中的胱抑素C浓度无显著差异。在不同条件下储存长达一个月的血清样本中，胱抑素C是稳定的。该方法与另一种市售的颗粒增强比浊免疫测定法相关性良好（平均差异=-0.536±0.307 mg/l）。在区分肾功能正常的患者和肾功能轻度至中度降低的患者方面，胱抑素C比肌酐具有更好的临床敏感性。该方法适用于常规的胱抑素C测定，包括急诊情况。
