Objective To investigate the importance of allowable total error (TEa) source in sigma(σ) metrics for assessing the analytical quality of clinical chemistry determination.Methods In this study, the data were collected from the second internal quality control of routine chemistry and the first external quality assessment of routine chemistry in 2014 organized by the National Center for Clinical Laboratory.One of the laboratories was selected for its coefficient of variation ( CV) and the bias of 19 clinical chemistry items from the data.σof 2 runs were calculated by 5 different TEa. The σmetrics′performance for assessing the analytical quality of clinical chemistry determination was analyzed comparatively.Results σmetrics varied with the changes of TEa and imprecision.Under the National Health Industry Standard, the majorσvalues(68.4%)for control 1 ranged from 2 to 4 and from 3 to 6 for control 2(58%).Under RiliBÄK, except triglyceride (negative) and alanine aminotransferase (ALT)(<3), others had aσvalue from 3 to 6, even up to 14.78.Under the Clinical Laboratory Improvement Amendment of 1988 (CLIA′88), 89.47% of control 1 showed aσvalue>3, up to 7.69, and 84.2% of control 2 showed a σvalue >3, up to 10.43.Under biological variability, theσvalue of control 1 ranged from 1 to 5, and the most (63%) was <3, and that of control 2 ranged from 1 to 6, but those of 9 from 19 were <3.Under the TEa of Australian, theσvalue of control 1 was <3, and that of 79%control 2 was <3 .The σvalue of control 2 was generally higher than that of control 1.Conclusions The 6σis an efficient way to control quality, but the lack of TEa for many analytes and inconsistent TEa from different sources are important variables for the interpretation ofσmetrics in a routine clinical laboratory.%目的：探讨不同允许总误差（ TEa）来源对西格玛（σ）度量评价实验室临床化学检验项目分析质量的重要性。方法用卫生部临床检验中心2014年第2次常规化学室内质控数据及2014年第1次常规化学室间质评某实验室19个检测项目的变异系数（ CV）及百分差值（用其估计偏移大小），结合5种不同标准TEa计算2个批次质控品的σ值。对比分析不同标准TEa计算的σ度量评价检测项目的分析质量。结果σ度量随TEa及不精密度水平而变化。使用行业标准TEa：质控品1的σ值有68．4％集中在2～4，质控品2有58％集中在3～6；使用德国RiliB橃K TEa标准：σ值除甘油三酯低至负值、丙氨酸氨基转移酶（ ALT）稍低于3外，其它项目的σ值均在3～6之间，高值可达14．78；使用美国CLIA′88 TEa：质控品1中有89．47％的σ值＞3，高值可达7．69，质控品2中有84．2％的σ值＞3，高值可达10．43；使用生物学变异（适当的） TEa：质控品1的σ值集中在1～5，其中63％＜3，质控品2集中在1～6，但19项中有9项的σ值＜3；使用澳大利亚的TEa：质控品1的σ值除1项外其余全部＜3，质控品2的σ值有79％＜3。质控品2的σ值普遍高于质控品1。结论6σ是一种更有效的质量控制方法，但很多检验项目缺少TEa，且不同来源TEa有时不一致。所以，对于常规临床实验室σ度量的解释意义重大。
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