12.2.8 回收率与精密度试验
12.2.8.1 精密度
精密度是表示测定结果与平均值的偏差程度，体现了方法的重现性。
取50µg/mL的克来夫定溶液2mL，加入人空白尿液至5mL，配制成含克来夫定20µg/mL的质控尿样。取上述尿样溶液以人空白尿液稀释成其他浓度的质控尿样，在同一批内按前述方法提取后进样测定，每一浓度测定5份，计算方法的批内精密度。按上述方法共测定3个连续分析批，将结果分别进行统计计算，得批间精密度。

12.2.8 Recovery and precision test

12.2.8.1 Precision: A method to demonstrate the deviation between results and mean reflects the reproducibility of method. Take 2mL of Clevudine solution with a concentration of 50µg/mL, add human blank urea to 5ml to prepare the quality control sample which contains 20µg/mL Clevudine. Take certain amount of above urea solution, dilute with human blank urea to obtain quality control samples of other concentrations. Within one run, perform tests on the samples extracted according to the above mentioned method, 5 samples for one concentration, then calculate the within-run precision of this method. Perform tests on 3 consecutive analytical lots according to the above method, and then conduct statistical calculation on the results respectively to get between-run precision.

从表14可见，本方法的批内和批间的RSD均<15%，说明本方法的精密度完全符合SFDA关于“化学药物临床药代动力学研究技术指导原则”的要求。
12.2.8.2 方法回收率(准确度)
取空白尿液加入克来夫定储备液，分别配制成低、中、高浓度的标准尿样溶液，按前述方法提取后进样测定，计算测定方法的回收率【方法回收率（%）=测定浓度 / 配置浓度100%】。结果见表15，表明本法的准确度符合要求。

From Table 14, within-run and between-run RSD are <15%, which shows that the precision of this method completely conforms to the requirements specified in SFDA ‘Guideline for clinical pharmacokinetics study technology of chemical drug’.

12.2.8.2 Recovery of the method (accuracy):

Add blank urea to Clevudine stock solution to prepare standard urea solutions of low, middle, and high concentration. After processed according to the aforementioned method, the samples are injected into the system. Calculate the recovery of this method (Recovery of this method (%) = Observed concentration/Assigned concentration). The results are presented in Table 15, which shows that the accuracy of this method conforms to the requirements specified in the guideline.

Table 15. Recovery for the determination of urea Clevudine concentration

12.2.8.3 基质效应
取六个不同来源的人空白尿液，按“血样前处理”项下操作至吸取上清液100L至干净试管中，分别用100L高、中、低浓度基质效应对照品溶液稀释，进LC-MS/MS分析，各组分的峰面积记作A基。另取流动相为溶剂的对照品溶液直接进样，各组分的峰面积记作A对。以A基/A对计算尿样处理方法的基质效应，结果见表16。表明尿样基质使克来夫定信号降低约20%，这种降低在不同受试者间的相对标准差RSD小于8%，因此本法受基质效应的影响小。方法学研究结果亦表明本法准确度、精密度均符合药动学研究要求。

12.2.8.3 Effect of the medium

Take six human blank urea samples of different origin, and transfer 100μL of supernatant to clean test tubes in accordance with ‘Pre-processing of plasma samples’. Dilute with 100μL of high, intermediate, and low concentration control solution for medium effect. Perform LC-MS/MS analysis, and record the peak area of each component as A_baseline. Take certain amount of control solution which uses mobile phase as solvent, and record the peak area of each component as A_reference. Calculate the ratio between A_baseline and A_reference as the effect of the medium, and all results are listed in Table 16. All data show that the effect of the medium for urea samples will decrease the signal of Clevudine by 20%, furthermore, this decrease result in the relative standard deviation (RSD) among different subjects less than 8%, therefore there is minimal medium effect on this method. Results generated in a methodology study demonstrate that the accuracy and precision of this method meet the requirements in pharmacokinetics investigation.

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