Statistical Methods In Epidemiology--general

该项目为流行病学开发了新的统计方法，具有广泛的应用，并根据正在进行的流行病学项目，特别是与生殖研究有关的项目，开发了所需的方法。今年的工作涉及几个项目。(1)一个项目涉及使用美国出生的双变量出生体重和孕长数据来估计和纠正使用最后一个月经期来估计孕长的测量误差。我们的最终目标是改进每个完整孕周的出生体重和方差标准，并纠正族裔和产妇年龄范围内估计的早产率。我们还希望在这些类别中改进对出生体重、孕长和围产儿死亡风险之间关系的评估。(2)另一个项目涉及以人体样本为基础的昂贵化验生物标记物的综合评估。早先的工作表明，在病例对照环境中，人们可以从病例集合和对照集合中收集样本，并进行基于集合的分析。通过略微修改的Logistic模型，该分析可以估计个体水平的风险参数，并且与基于个体分析的分析相比几乎没有损失。这意味着，如果暴露是基于昂贵的使用人类样本的测试，那么在测试之前将样本汇集在一起可以显著提高效率。在最近的工作中，我们已经将这些方法扩展到应用于精细匹配的病例对照设计和怀孕时间数据。对于后一种设计，一个人在受孕前定义的地层内汇集标本。同样，与单独的水平分析相比，电力几乎不会受到影响，成本大大降低。总的来说，汇集的另一个巨大好处是它保守地使用了不可替代的人类标本。例如，将标本以3个为一组，将每个标本所需的数量减少2/3。(3)第三个项目开发了改进的方法，用于根据生物标记物相对于假阳性和假阴性预测的纵向测量来评估对未来事件预测的准确性。 目前正在审查一份关于在精确匹配的病例对照研究中设计和分析合并暴露评估的方法的文件，一份建议和评估在环境因素对生育影响的怀孕时间研究中使用合并评估的文件即将提交。目前正在编写一份关于提高特定孕龄出生体重标准的论文。一篇基于对一项涉及生物标记物的纵向研究的预测进行评估的论文发表在《生物统计学》杂志上，该领域的另一篇论文正在进行审查。

This project develops new statistical methods for epidemiology with broad applications and also methods as needed for ongoing projects in epidemiology, particularly those related to reproductive studies. The work this year involved several projects. (1) One project concerned using the bivariate birth weight and gestational length data for US births to estimate and correct for measurement errors in use of last menstrual period for estimating gestational length. Our goal is ultimately to develop improved standards for birth weights and variances for each completed week of gestation and also to correct the estimated rates of preterm birth within ethnic and maternal age categories. We also hope to improve the assessment of the relationship between birth weight, gestational length and risk of perinatal mortality within those categories. (2) Another project concerns pooled assessment of expensive-to-assay biomarkers based on human samples. Earlier work had shown that in a case-control setting one can pool together specimens from sets of cases and sets of controls and carry out a set-based analysis. With a slightly modified logistic model that analysis can estimate the individual-level risk parameters and loses almost no power compared to analysis based on individual assays. This means that if an exposure is based on an expensive assay that uses human samples, one can markedly improve efficiency by pooling specimens prior to assay. In recent work, we have extended these methods to apply to a fine-matched case-control design and also to time-to-pregnancy data. With the latter design, one pools specimens within strata defined by the time to conception. Again the power suffers almost not at all, compared to individual level assays, and the costs are greatly reduced. Another great benefit to pooling in general is in its conservative use of irreplaceable human specimens. For example, pooling specimens in sets of 3 reduces the amount needed from each specimen by 2/3. (3) A third project developed improved methods for assessing the accuracy of prediction of future events based on longitudinal measures of a biomarker in relation to false positive and false negative predictions. A paper based on methods for design and analysis of pooled exposure assessments in fine-matched case-control studies is currently undergoing review, and one that proposes and evaluates the use of pooling in time-to-pregnancy studies of fertility effects of environmental factors is soon to be submitted. A paper based on improving birth weight standards for specific gestational ages is currently in preparation. A paper based on assessing prediction in a longitudinal study involving a biomarker was published in Biometrics and another in this area is undergoing review.