BACKGROUND Cystatin C is a key GFR biomarker. Recently, Siemens recalibrated the assay based on certified reference material ERM-DA471/IFCC. The NIH-funded longitudinal chronic kidney disease in children (CKiD) study has > 3000 cystatin C measurements based on a pre-IFCC calibrator provided by Siemens. Since cystatin C values for CKiD are now standardized to IFCC certified reference material, it is important to relate the IFCC-calibrated results to the previous values so that there are no discontinuous results. METHODS We diluted cystatin C ERM-DA471/IFCC (5.48 mg/L) into buffer and compared results with predicted ones. We then updated the cystatin C application on our BN II nephelometer to provide results based on pre-IFCC and IFCC calibrations of CKiD specimens simultaneously. We assayed 51 previously analyzed sera and 62 fresh additional specimens. RESULTS The predicted concentrations from the IFCC standard were consistently 17% higher than the measured values using the pre-IFCC calibration (y = 1.1686x). Similarly, the re-run and fresh sample concentrations were 17% higher via the IFCC calibration than by the pre-IFCC calibration (y = 1.168x). There was very high reliability in the measurements using the previous calibration for re-run specimens (0.99) and for 33 pristine specimens using IFCC calibration (0.99). CONCLUSIONS We confirm the recalibration proposed by Siemens. To convert pre-IFCC results to IFCC-calibrated concentrations, the value is multiplied by 1.17. Conversely, one divides IFCC-calibrated results by 1.17 to estimate GFR via previously published pre-IFCC CKiD eGFR equations. For older adolescents, cystatin C has already been standardized and can be directly applied to the CKD-EPI equations.

中文翻译：

---

使用西门子浊度计中的标准化材料对半胱氨酸蛋白酶抑制剂C进行重新校准。

背景胱抑素C是关键的GFR生物标志物。最近，西门子根据认证的参考材料ERM-DA471 / IFCC重新校准了该测定法。美国国家卫生研究院（NIH）资助的儿童纵向慢性肾脏病（CKiD）研究基于西门子提供的IFCC预先校准器进行了3000多次胱抑素C测量。由于CKiD的半胱氨酸蛋白酶抑制剂C值现在已根据IFCC认证的参考材料进行了标准化，因此将IFCC校准的结果与以前的值联系起来很重要，这样就不会出现不连续的结果。方法我们将半胱氨酸蛋白酶抑制剂C ERM-DA471 / IFCC（5.48 mg / L）稀释至缓冲液中，并将结果与​​预测值进行比较。然后，我们在BN II浊度计上更新了胱抑素C的应用，以同时基于CKiD标本的IFCC前和IFCC校准提供结果。我们分析了51个先前分析的血清和62个新鲜的其他标本。结果IFCC标准的预测浓度始终比使用IFCC之前的标定值（y = 1.1686x）高17％。同样，通过IFCC校准，重新运行和新鲜样品的浓度比IFCC之前的校准高（y = 1.168x）17％。对于重新运行的样品，使用先前的校准（0.99），使用IFCC校准的33个原始样品（0.99），测量具有很高的可靠性。结论我们确认了西门子提议的重新校准。要将IFCC之前的结果转换为IFCC校准浓度，请将该值乘以1.17。相反，人们可以将IFCC校准结果除以1.17，从而通过先前发布的IFCC CKiD eGFR预先方程式估算GFR。对于年龄较大的青少年，