Department of Chemical Pathology, Pathology Queensland, Brisbane, Queensland, Australia.
Clin Chim Acta. 2012 Nov 12;413(21-22):1786-91. doi: 10.1016/j.cca.2012.07.001. Epub 2012 Jul 10.
The diagnosis of myocardial infarction is in part predicated on a rise and/or fall in cardiac troponin (cTn). z-Values incorporate analytical and biological variation to standardize serial differences: z=Δ/√[2SD²(Analytical) + 2SD²(Biological)]. We investigated the theoretical distributions of actual differences (Δ), relative differences (%Δ) and z-values and compared the agreement in classification of differences measured on four contemporary platforms.
cTn was measured in 575 sample pairs on the Abbott Architect cTnI, Beckman Coulter Access2 cTnI, Roche Cobas cTnT and Siemens ADVIA Centaur cTnI methods.
Good agreement was obtained amongst all methods with a universal z-value cut-off (κ>0.79) and method specific fixed Δ cut-offs (κ>0.82) while suboptimal agreement was obtained between cTnI and cTnT with fixed %Δ cut-offs (κ<0.50).
Fixed Δ cut-offs will perform well at low cTn concentrations while fixed %Δ cut-off values are predicted to perform poorly. z-Values are independent of the cTn concentration, present differences as a continuum of probability and a universal decision level can be used for all cTnI and cTnT methods.
心肌梗死的诊断部分取决于心肌肌钙蛋白（cTn）的升高和/或降低。z 值结合分析和生物学变异来标准化连续差异：z=Δ/√[2SD²（分析）+2SD²（生物学）]。我们研究了实际差异（Δ）、相对差异（%Δ）和 z 值的理论分布，并比较了在四个当代平台上测量的差异分类的一致性。
在 Abbott Architect cTnI、Beckman Coulter Access2 cTnI、Roche Cobas cTnT 和 Siemens ADVIA Centaur cTnI 方法上测量了 575 对样本。
所有方法之间都获得了良好的一致性，具有通用的 z 值截断值（κ>0.79）和特定方法的固定 Δ 截断值（κ>0.82），而 cTnI 和 cTnT 之间使用固定 %Δ 截断值则获得了不理想的一致性（κ<0.50）。
固定 Δ 截断值在 cTn 浓度较低时表现良好，而固定 %Δ 截断值预计表现不佳。z 值不依赖于 cTn 浓度，将差异表示为概率的连续体，并且可以为所有 cTnI 和 cTnT 方法使用通用的决策水平。
