Statistical Methods In Epidemiology--general

该项目为流行病学开发新的统计方法，具有广泛的应用，并为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妊娠长度数据来估计和校正使用末次月经估计妊娠长度的测量误差。 我们的目标是最终制定出生体重的改进标准和每个完整妊娠周的差异，并纠正种族和母亲年龄类别中的早产估计率。 我们还希望改进对这些类别中出生体重、妊娠期长短和围产期死亡率风险之间关系的评估。(2)另一个项目涉及基于人类样本的昂贵生物标志物的汇总评估。早期的工作表明，在病例对照设置中，可以将病例组和对照组的样本汇集在一起，并进行基于集合的分析。 通过略微修改的逻辑模型，该分析可以估计个体水平的风险参数，并且与基于个体测定的分析相比几乎没有损失功效。 这意味着，如果暴露是基于使用人体样本的昂贵测定，则可以通过在测定前合并样本来显著提高效率。在最近的工作中，我们已经将这些方法扩展到适用于精细匹配的病例对照设计和妊娠时间数据。 在后一种设计中，人们将样本集中在由受孕时间定义的地层中。 同样，与单个水平测定相比，功率几乎完全不受影响，并且成本大大降低。一般来说，共享的另一个巨大好处是保守地使用不可替代的人类标本。例如，将样本合并为3个样本组可将每个样本所需的样本量减少2/3。 (3)第三个项目开发了改进的方法，用于评估基于生物标志物的纵向测量与假阳性和假阴性预测相关的未来事件预测的准确性。 目前正在审查一份基于精确匹配病例对照研究中合并暴露评估的设计和分析方法的文件，不久将提交一份建议和评估在环境因素生育力影响的妊娠时间研究中使用合并的文件。目前正在编写一份关于改进特定胎龄婴儿出生体重标准的文件。 一篇基于评估涉及生物标志物的纵向研究中的预测的论文发表在《生物统计学》上，该领域的另一篇论文正在审查中。

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.