Evaluating changes in coronary artery calcium: An analytic method that accounts for interscan variability
Evaluating changes in coronary artery calcium: An analytic method that accounts for interscan variability
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DOI：
10.2214/ajr.182.5.1821327
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发表时间：
2004-05-01
影响因子：
5
通讯作者：
Rewers, M
中科院分区：
文献类型：
--
作者：
Hokanson, JE;MacKenzie, T;Rewers, M
目标。电子束CT测量冠状动脉钙与冠状动脉疾病相关，可用于预测冠状动脉疾病事件。调查冠状动脉钙变化的研究需要解决扫描间变异性，因为它与冠状动脉钙的总体评分有关，可以定义冠状动脉钙随时间的进展或消退。研究对象和方法。对1074名参与者进行了电子束CT扫描。间隔5分钟重复冠状动脉钙容量评分。采用Bland-Altman图和同质性检验检验扫描间变异性。将Box-Cox族变换（包括幂、根和对数）应用于钙体积评分。将稳定钙容量评分变化的转化应用于109例糖尿病患者钙容量评分的进展。钙体积评分的变异性随着冠状动脉钙水平的升高而增大（rho = 0.67，钙体积评分的绝对差值与平均值的关系p < 0.001）。使用钙体积评分的平方根变换消除了这种异质性（rho = 0.09, p < 0）。15为钙体积评分平方根绝对差值与钙体积评分均方根差值的关系)。这一转变应用于109名糖尿病患者平均间隔2.7年的钙体积评分。钙体积评分的显著变化被定义为均方根转换为钙体积评分之间的差异大于或等于2.5 mm(3)（>第99百分位数的扫描间变异性）。在10%的受试者中观察到显著进展。钙容量评分的平方根纠正了由于冠状动脉钙水平导致的钙容量进展偏差。利用钙容量评分的平方根稳定了冠状动脉钙含量范围内的扫描间变异性。将冠状动脉钙的变化定义为大于或等于2.5 mm3的平方根变换钙体积分数的差异，提供了一个关于基线冠状动脉钙的无偏估计。这种分析技术可能有助于研究冠状动脉钙变化与临床结果的相关性，并在临床试验中使用冠状动脉钙变化作为治疗对亚临床疾病影响的衡量标准。
OBJECTIVE. Coronary calcium measured by electron beam CT is associated with coronary disease and can be used to predict coronary disease events. Studies investigating changes in coronary calcium need to address interscan variability as it relates to the overall coronary calcium score in defining progression or regression of coronary calcium over time.SUBJECTS AND METHODS. Electron beam CT was performed on 1,074 participants. Coronary calcium volume scores were repeated 5 min apart. Interscan variability was examined using Bland-Altman plots and homogeneity tests. Transformations of the Box-Cox family (including power, roots, and logarithm) were applied to calcium volume scores. The transformation that stabilized the variation in calcium volume scores was applied to progression of calcium volume scores in 109 subjects with diabetes.RESULTS. The variability in calcium volume score increased as the level of coronary calcium increased (rho = 0.67, p < 0.001 for the relation between the absolute difference and the mean value of calcium volume scores). This heterogeneity was removed using the square root transformation of the calcium volume score (rho = 0.09, p < 0. 15 for the relation between the absolute difference in the square root of the calcium volume score and the mean square root of the calcium volume score). This transformation was applied to calcium volume scores taken a mean of 2.7 years apart in 109 subjects with diabetes. A significant change in calcium volume score was defined as a difference between the square root-transformed to calcium volume scores greater than or equal to 2.5 mm(3) (> 99th percentile of interscan variability). Significant progression was observed in 10% of the subjects. The square root of the calcium volume score corrected for the bias in progression of calcium volume because of the level of coronary calcium.CONCLUSION. Using the square root of the calcium volume score stabilized interscan variability across the range of coronary calcium. Defining change in coronary calcium as greater than or equal to 2.5 mm3 of the difference in the square root-transformed calcium volume scores provided an estimate that was unbiased with respect to baseline coronary calcium. This analytic technique may facilitate investigations of the relevance of changes in coronary calcium to clinical outcomes and the use of changes in coronary calcium as a measure of the therapeutic impact on subclinical disease in clinical trials.