We report here validation of the Immulite 2000 Xpi cortisol immunoassay (Siemens; with kit lot numbers <550) for measurement of urine cortisol in dogs, with characterization of the precision (CV), accuracy (spiking-recovery [SR] bias), and observed total error (TEo = bias + 2CV) across the reportable range. Linearity assessed by simple linear regression was excellent. Imprecision, SR bias, and TEo increased markedly with decreasing urine cortisol concentration. Interlaboratory comparison studies determined range-based (RB) bias and average bias (AB). The 3 biases (SR, RB, and AB) and resulting TEo differed markedly. At 38.6 and 552 nmol/L (1.4 and 20 μg/dL), between-run CVs were 10% and 4.5%, respectively, and TEo_RB were ~30% and 20%, respectively, similar to observations in serum in another validation study. These analytical performance parameters should be considered for urine cortisol:creatinine ratio (UCCR) result interpretation, given that, for any hypothetical errorless urine creatinine measurement, the error % on UCCR mirrors the error % on urine cortisol. Importantly, there is no commonly used interpretation threshold for UCCR, given that UCCR varies greatly depending on measurement methods and threshold computation. To date, there is no manufacturer-provided quality control material (QCM) with target values for urine cortisol with an Immulite; for Liquicheck QCM (Bio-Rad), between-run imprecision was ~5% for both QCM levels. Acceptable QC rules are heavily dependent on the desired total allowable error (TEa) for the QCM system, itself limited by the desired clinical TEa.

我们在此报告了 Immulite 2000 Xpi 皮质醇免疫测定法（西门子；试剂盒批号 <550）的验证，用于测量狗的尿液皮质醇，具有精确度 (CV)、准确度（尖峰恢复 [SR] 偏差）的表征，以及在可报告范围内观察到的总误差（TEo = 偏差 + 2CV）。通过简单线性回归评估的线性非常好。随着尿皮质醇浓度的降低，不精确性、SR 偏差和 TEo 显着增加。实验室间比较研究确定了基于范围 (RB) 的偏差和平均偏差 (AB)。3 个偏差（SR、RB 和 AB）和由此产生的 TEo 显着不同。在 38.6 和 552 nmol/L（1.4 和 20 μg/dL）下，运行间 CV 分别为 10% 和 4.5%，TEo _RB分别约为 30% 和 20%，与另一项验证研究中血清中的观察结果相似。这些分析性能参数应考虑用于尿皮质醇：肌酐比值 (UCCR) 结果的解释，因为对于任何假设的无误差尿肌酐测量值，UCCR 的误差百分比反映了尿皮质醇的误差百分比。重要的是，UCCR 没有常用的解释阈值，因为 UCCR 因测量方法和阈值计算而异。迄今为止，没有制造商提供的质量控制材料 (QCM) 具有含 Immulite 的尿皮质醇目标值；对于 Liquicheck QCM (Bio-Rad)，两个 QCM 水平的运行间不精密度约为 5%。可接受的 QC 规则在很大程度上取决于 QCM 系统所需的总允许误差 (TEa)，