Barbara Davis Center for Childhood Diabetes, University of Colorado-Denver, PO Box 6511, Mail Stop A140, Aurora, CO 80045, USA.
Clin J Am Soc Nephrol. 2011 Aug;6(8):1952-5. doi: 10.2215/CJN.11271210. Epub 2011 Jul 22.
Cystatin C is used increasingly as a biomarker of renal function; however, cystatin C assays are not standardized. Our objective was to compare cystatin C results within the Coronary Artery Calcification in Type 1 Diabetes (CACTI) study over time and in repeated measures to evaluate for assay drift.
DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Serum samples were obtained at baseline (visit 1 [V1], 2000 to 2002) and follow-up (visit 2 [V2], 2003 to 2005; visit 3 [V3], 2006 to 2008) and were assayed in 2006 (V1), 2007 to 2008 (V2), and 2010 (V3) in the same laboratory.
Mean cystatin C levels measured using the Dade-Behring assay decreased over time in subjects, with measures at all three visits (V1: 0.80 ± 0.19 [0.42 to 3.41], V2: 0.75 ± 0.22 [0.39 to 3.77], and V3: 0.69 ± 0.22 [0.39 to 3.79]). Cystatin C values were lower in V1 and V2 samples remeasured in 2010 (mean differences -0.13 ± 0.04 and -0.08 ± 0.04, P < 0.0001 for both). Correlations for original and re-run values were strong for V1 (r = 0.99) and V2 (r = 0.99). Deming regression equations and Bland-Altman plots suggest a systematic shift in the values over time.
Systematic shifts in cystatin C levels, which can be corrected by regression adjustment, occurred in our laboratory in samples measured in 2006 and 2007 to 2008 as compared with 2010. Assay standardization and measurement reliability for cystatin C must be addressed.
胱抑素 C 作为肾功能的生物标志物的应用日益广泛，但胱抑素 C 检测并未标准化。我们的目的是比较冠状动脉钙化在 1 型糖尿病中的作用（CACTI）研究中随时间推移和重复测量的胱抑素 C 结果，以评估检测漂移。
设计、设置、参与者和测量：于 2000 年至 2002 年（第 1 次就诊 [V1]）和 2003 年至 2005 年（第 2 次就诊 [V2]）时收集基线血清样本，并于 2006 年（V1）、2007 年至 2008 年（V2）和 2010 年（V3）在同一家实验室进行检测。
使用 Dade-Behring 检测方法测量的胱抑素 C 水平随时间的推移在研究对象中逐渐降低，所有三次就诊（V1：0.80 ± 0.19 [0.42 至 3.41]，V2：0.75 ± 0.22 [0.39 至 3.77]和 V3：0.69 ± 0.22 [0.39 至 3.79]）的测量值均较低。2010 年重新测量 V1 和 V2 样本时，胱抑素 C 值较低（平均值差异分别为-0.13 ± 0.04 和-0.08 ± 0.04，均＜0.0001）。原始值和重新运行值的相关性在 V1（r = 0.99）和 V2（r = 0.99）中均很强。Deming 回归方程和 Bland-Altman 图表明，随着时间的推移，值存在系统偏差。
与 2010 年相比，我们实验室在 2006 年和 2007 年至 2008 年测量的样本中，胱抑素 C 水平发生了系统性变化（可通过回归校正）。必须解决胱抑素 C 的检测标准化和测量可靠性问题。
