Chetty M, Wilson J F
Department of Experimental and Clinical Pharmacology, University of the Witwatersrand, South Africa.
Ther Drug Monit. 1999 Apr;21(2):215-8. doi: 10.1097/00007691-199904000-00012.
The accuracy and the precision with which a drug concentration is quantified in the blood has a significant impact on the therapeutic drug monitoring (TDM) of the drug. In the absence of a system of accreditation of laboratories in South Africa, this study was designed to compare the accuracy and the precision of the measurement of antiepileptic drugs by 24 South African laboratories with those of non-South African laboratories that participate in the United Kingdom National External Quality Assessment Scheme (UKNEQAS). Three test samples, containing a range of concentrations of phenytoin, valproate, carbamazepine, and phenobarbitone spiked into newborn calf serum were distributed to participating laboratories, which were asked to measure the serum concentrations using their routine assay method. Coefficients of variation were used to assess precision of measurements, and the percentage difference of the consensus mean from the spike value was used as an assessment of accuracy. There was comparable precision in the measurements for both the South African and the non-South African groups. However, there appeared to be a difference in the accuracy of measurement between the two groups. It was noted that the majority (77%) of the South African laboratories used the Abbott fluorescence polarization immunoassay (FPIA) with TDx analyzers (Abbott Laboratories, Abbott Park, IL, USA). Further analysis of the results of the South African and UKNEQAS subgroups using the FPIA technique showed a reduction in statistic bias, suggesting that part of the explanation for the statistic difference in the accuracy may be an intertechnique bias related to the use of a nonhuman matrix for sample preparation. Additional studies are required to determine other causes for the statistic differences in accuracy. However, the differences in accuracy are unlikely to be of clinical significance.
血液中药物浓度定量的准确性和精密度对药物的治疗药物监测（TDM）有重大影响。在南非缺乏实验室认可体系的情况下，本研究旨在比较24家南非实验室与参与英国国家外部质量评估计划（UKNEQAS）的非南非实验室对抗癫痫药物测量的准确性和精密度。将含有一系列浓度的苯妥英、丙戊酸盐、卡马西平和苯巴比妥掺入新生小牛血清的三个测试样品分发给参与实验室，要求它们使用常规检测方法测量血清浓度。变异系数用于评估测量的精密度，共识均值与加标值的百分比差异用作准确性评估。南非组和非南非组的测量精密度相当。然而，两组之间的测量准确性似乎存在差异。值得注意的是，大多数（77%）南非实验室使用配备TDx分析仪的雅培荧光偏振免疫分析法（FPIA）（雅培实验室，美国伊利诺伊州雅培公园）。使用FPIA技术对南非和UKNEQAS亚组的结果进行进一步分析显示统计偏差有所降低，这表明准确性统计差异的部分原因可能是与使用非人类基质进行样品制备相关的技术间偏差。需要进行更多研究以确定准确性统计差异的其他原因。然而，准确性差异不太可能具有临床意义。
