Detection of two-component mixtures of lognormal distributions in grouped, doubly truncated data: analysis of red blood cell volume distributions.
Detection of two-component mixtures of lognormal distributions in grouped, doubly truncated data: analysis of red blood cell volume distributions.
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DOI：
10.2307/2532150
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发表时间：
1991-06
期刊：
影响因子：
1.9
通讯作者：
C. McLaren;M. Wagstaff;G. Brittenham;A. Jacobs
中科院分区：
文献类型：
--
作者：
C. McLaren;M. Wagstaff;G. Brittenham;A. Jacobs
我们研究了当样本量很大时检测双截断数据中两个对数正态分布的混合的统计要求。期望最大化算法用于参数估计。引导方法用于使用似然比统计来测试分布的混合。对计算机模拟混合物的分析表明，随着均值之差与最小标准差之比的增加，检测能力也会增加，参数估计的准确性也会提高。这些程序用于检查血液样本中红细胞体积的分布。每个分布都经过双重截断，以消除人为的频率计数，并测试与单个对数正态分布或两个对数正态分布的混合的最佳拟合。从 60 名健康个体获得的样本中发现了单一群体。在体外制备的 27 份血液混合物中的 25 份中检测到了两种细胞亚群。对 40 名接受缺铁性贫血治疗的患者的血液混合物进行的分析表明，在治疗开始后 6 周即可检测到所有亚群。为了确定是否可以检测到两种成分的混合物，对未输血的难治性贫血患者的分布进行了检查。在两名患有遗传性铁粒幼细胞贫血的患者中，发现了小细胞和正细胞的混合物，而在第三名患者中，发现了单一的小细胞群。在先前被确定为遗传性铁粒幼细胞贫血携带者的两个家庭成员中，发现了小细胞和正细胞亚群的混合物。对 25 名患有获得性骨髓增生异常性贫血的患者进行了检查。在两个中发现了与含有异常小细胞或大细胞细胞的亚群混合物的良好拟合。我们已经证明，在样本量较大的情况下，即使分布看起来是单峰的，也可以检测到分布的混合。这些统计技术提供了一种表征和量化贫血红细胞亚群变化的方法，但也可以应用于任何分组的双截断数据集，以测试是否存在两种对数正态分布的混合。
We have examined the statistical requirements for the detection of mixtures of two lognormal distributions in doubly truncated data when the sample size is large. The expectation-maximization algorithm was used for parameter estimation. A bootstrap approach was used to test for a mixture of distributions using the likelihood ratio statistic. Analysis of computer simulated mixtures showed that as the ratio of the difference between the means to the minimum standard deviation increases, the power for detection also increases and the accuracy of parameter estimates improves. These procedures were used to examine the distribution of red blood cell volume in blood samples. Each distribution was doubly truncated to eliminate artifactual frequency counts and tested for best fit to a single lognormal distribution or a mixture of two lognormal distributions. A single population was found in samples obtained from 60 healthy individuals. Two subpopulations of cells were detected in 25 of 27 mixtures of blood prepared in vitro. Analyses of mixtures of blood from 40 patients treated for iron-deficiency anemia showed that subpopulations could be detected in all by 6 weeks after onset of treatment. To determine if two-component mixtures could be detected, distributions were examined from untransfused patients with refractory anemia. In two patients with inherited sideroblastic anemia a mixture of microcytic and normocytic cells was found, while in the third patient a single population of microcytic cells was identified. In two family members previously identified as carriers of inherited sideroblastic anemia, mixtures of microcytic and normocytic subpopulations were found. Twenty-five patients with acquired myelodysplastic anemia were examined. A good fit to a mixture of subpopulations containing abnormal microcytic or macrocytic cells was found in two. We have demonstrated that with large sample sizes, mixtures of distributions can be detected even when distributions appear to be unimodal. These statistical techniques provide a means to characterize and quantify alterations in erythrocyte subpopulations in anemia but could also be applied to any set of grouped, doubly truncated data to test for the presence of a mixture of two lognormal distributions.