Abstract

Measurement imprecision is usually calculated from measurement results of the same stabilized control material(s) obtained over time, and is therefore, principally, only valid at the concentration(s) of the selected control material(s). The resulting uncertainty has been obtained under reproducibility conditions and corresponds to the conventional analytical goals. Furthermore, the commutability of the control materials used determines whether the imprecision calculated from the control materials reflects the imprecision of measuring patient samples. Imprecision estimated by measurements of patient samples uses fully commutable samples, freely available in the laboratories. It is commonly performed by calculating the results of routine patient samples measured twice each. Since the duplicates are usually analysed throughout the entire concentration interval of the patient samples processed in the laboratory, the result will be a weighted average of the repeatability imprecision measured in the chosen measurement intervals or throughout the entire interval of concentrations encountered in patient care. In contrast, the uncertainty derived from many measurements of control materials over periods of weeks is usually made under reproducibility conditions. Consequently, the repeatability and reproducibility imprecision play different roles in the inference of results in clinical medicine. The purpose of the present review is to detail the properties of the imprecision calculated by duplicates of natural samples, to explain how it differs from imprecision calculated from single concentrations of control materials, and to elucidate what precautions need to be taken in case of bias, e.g. due to carry-over effects.

摘要

测量不精确度通常是根据随时间推移获得的相同稳定控制材料的测量结果计算得出的，因此，原则上仅在所选控制材料的浓度下有效。在重现性条件下获得了不确定性，并且与常规分析目标相对应。此外，所使用的对照材料的可交换性确定了从对照材料计算出的不准确性是否反映了测量患者样品的不准确性。通过对患者样本进行测量而估计的不精确度使用可在实验室免费获得的完全可交换样本。通常通过计算每次两次测量的常规患者样品的结果来执行。在选定的测量间隔中或在患者护理中遇到的整个浓度间隔中测量的重复性不精确度的加权平均值。相比之下，在数周的时间内从许多对照材料测量中得出的不确定性通常是在可重复性下得出的条件。因此，重复性和再现性的不准确性在临床医学结果的推断中起着不同的作用。本文的目的是详细介绍由自然样品重复计算得出的不精确度的特性，解释其与由单一浓度的对照材料计算出的不精确度有何不同，并阐明在出现偏倚的情况下需要采取哪些预防措施，例如由于残留效应。