Reliability of longitudinal ultrasonographic measurements of carotid intimal-medial thicknesses
Reliability of longitudinal ultrasonographic measurements of carotid intimal-medial thicknesses
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DOI：
10.1161/01.str.27.3.480
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发表时间：
1996-03-01
期刊：
影响因子：
8.3
通讯作者：
Furberg, CD
中科院分区：
文献类型：
--
作者：
Espeland, MA;Craven, TE;Furberg, CD
背景与目的：颈动脉内膜中层厚度(IMT)的B型超声系列测量常被用来描述动脉粥样硬化的进展。这份报告描述了多中心临床试验中颈动脉IMT测量的纵向可靠性，量化了读者之间的差异造成的误差，并讨论了如何有效地设计研究。方法使用为期3年的无症状颈动脉进展研究(ACAPS；以前的无症状颈动脉斑块研究)的颈动脉IMT连续B型测量，以估计系统读者效应、非可视化和非系统误差对纵向测量误差的贡献，并描述作为观察数据基础的“真实”进展率的分布。方差分量是根据随机效应模型估计的，该模型适用于通过平均来自不同组颈动脉壁的IMT而形成的结果测量。结果在测量的IMT总方差中，11%可归因于读者之间的系统差异。非可视化的贡献不到7%。因此，主要的误差来源没有被计算在内(即随机误差或“噪声”，在我们的分析中，它包括任何漂移、非线性和超声仪的差异)。对于采用与ACAPS类似的测量方案的研究，描述队列的平均进展率需要2年或更长时间的随访期，而对个体内进展期进行分类则需要6年或更长时间。在为期3年的研究中，低至237的样本量为检测与IMT进展相关的危险因素提供了90%的统计能力。结论ACAPS测量方案提供了高度可靠的连续IMT数据。使用B型结果进行中等规模的多中心研究是可行的。
Background and Purpose Serial ultrasonic B-mode measurements of intimal-medial thickness (IMT) of the carotid artery are commonly used as surrogates for describing atherosclerosis progression. This report describes the longitudinal reliability of IMT measurement during a multicenter clinical trial, quantifies the error attributable to differences among readers, and discusses how studies can be efficiently designed.Methods Serial B-mode measurements of carotid IMT from the 3-year Asymptomatic Carotid Artery Progression Study (ACAPS; formerly Asymptomatic Carotid Artery Plaque Study) were used to estimate the contributions to longitudinal measurement error of systematic reader effects, nonvisualization, and nonsystematic error and to describe the distribution of ''true'' progression rates that underlie the observed data. Variance components were estimated from random-effects models fitted to outcome measures formed by averaging IMTs from different sets of carotid artery wails. These were used to contrast the relative efficiency of study designs.Results Of the total variance of measured IMT, 11% was attributable to systematic differences among readers. Nonvisualization contributed less than 7%. Thus, the predominant source of error was unaccounted for (ie, random error or ''noise,'' which in our analyses included any drift, nonlinearity, and sonographer differences). For studies with measurement protocols similar to ACAPS, follow-up times of 2 years or more are desirable for describing the mean progression rates of cohorts, and of 6 years or more for categorizing progression within individuals. In 3-year studies, sample sizes as low as 237 provide 90% statistical power for detecting risk factors that have correlations with IMT progression of .50 or greater.Conclusions The ACAPS measurement protocol provided highly reliable serial IMT data. Moderate-sized multicenter studies using B-mode outcomes are feasible.