Intraclass correlation coefficient for school-based HIV/STI prevention trials

描述(申请人提供)：这项R03研究项目的特点是对四项以学校为基础的艾滋病毒/性传播感染预防干预措施的联邦资助纵向分组随机试验(GRT)的数据集进行二次分析，以向现场提供所需的组内相关系数(ICCs)估计--这是确定在规划GRT时以足够的力量和精度估计干预效果所需的样本量的关键参数。研究表明，ICC估计因结果、人口、环境和研究设计的不同而有很大差异，ICC估计的微小变化可以对研究的力量和精确度产生很大影响(Murray，1998；Donner和Klar，2000；Rotondi和Donner，2009；ResNicow等人，2010)。因此，在过去的十年里，研究人员被敦促公布对更广泛的结果、人群和环境的估计，以便能够更有效地计划未来的试验(Murray等人，2004；ResNicow等人，2010；Murray和Blitstein，2003；Pals等人，2009)。该项目将采用两级(学生在学校内嵌套)和三级(学生在学校内嵌套的教室内嵌套)多级别模型来分析每个数据集的横截面，以向实地提供第一组学校级别的ICC估计，专门用于规划侧重于性风险承担结果的学校艾滋病毒预防干预措施的横断面和测试前/测试后GRT。此外，在方法和软件方面的最新进展提供了在计划纵向GRT时通过使用来自三水平重复测量模型的ICC或方差分量参数的估计来改进样本量确定的可能性。然而，在任何健康风险预防领域发表的对这些参数的估计很少(Murray和Blitstein，2003；Murray等人，2006；Murray等人，2007；Moonseong和Leon，2008；Spybrook等人，2009)。这项研究将使用重复测量多水平模型来获得这些参数的初步估计，以规划以学校为基础的艾滋病毒预防干预措施的纵向GRT。在所有情况下，将对协变量进行调整和不对协变量进行调整的模型进行分析，以提供关于协变量调整可以在多大程度上减少艾滋病毒/性传播感染预防干预措施的学校GRT中的ICC和所需样本量的信息。还将审查各种ICC和方差分量估计对检测常见效应大小所需样本大小的影响。这项研究的结果将通过同行评议的文章和会议发言提供，以便使规划未来以学校为基础的艾滋病毒/性传播感染预防研究的研究人员受益。鉴于学校作为向青少年提供预防干预措施的场所的重要性以及实施以学校为基础的GRTS的相关成本，有效规划这些试验至关重要。 与公共卫生相关：学校是艾滋病毒/性传播感染预防干预的重要场所，因为大多数年轻人都在上学，这使他们成为有效实施方案的场所。严格评估这些干预措施至关重要，以确保公共卫生资源用于对青年艾滋病毒和其他性传播感染的发病率产生重大影响的项目。严格评估以学校为基础的艾滋病毒预防干预措施的黄金标准是团体随机试验(GRT)，但用足够的力量和精度估计干预效果所需的样本量(学校/学生数量)来规划此类试验，需要从涉及类似结果、人群和环境的研究中估计组内相关系数(ICC)参数。该项目将提供针对各种不同学校环境和人群的艾滋病毒/性传播感染相关行为和心理社会结果的首个ICC参数估计，以便该领域的研究人员可以选择最合适的ICC来有效地评估这些昂贵的研究。

DESCRIPTION (provided by applicant): This R03 research project features secondary analyses of datasets from four federally-funded longitudinal group randomized trials (GRTs) of school-based HIV/STI prevention interventions to provide the field with needed estimates of intraclass correlation coefficients (ICCs) - a parameter critical for determining the sample size necessary for estimating intervention effects with adequate power and precision when planning GRTs. Studies have shown that ICC estimates vary widely depending on the outcome, population, setting, and study design, and small changes in ICC estimates can have large effects on study power and precision (Murray, 1998; Donner and Klar, 2000; Rotondi and Donner, 2009; Resnicow et al., 2010). Consequently, in the past decade researchers have been urged to publish estimates for a wider variety of outcomes, populations and settings so that future trials can be planned more efficiently (Murray et al., 2004; Resnicow et al., 2010; Murray and Blitstein, 2003; Pals et al., 2009). This project would employ 2-level (students nested within schools) and 3-level (students nested within classrooms nested within schools) multilevel models to analyze cross sections of each dataset to provide the field with the first set of school-level ICC estimates specific to planning cross- sectional and pretest/posttest GRTs of school-based HIV prevention interventions focused on sexual risk- taking outcomes. In addition, recent advances in methodology and software provide the potential to refine sample size determinations when planning longitudinal GRTs by using estimates of ICC or variance component parameters from 3-level repeated measures models. Yet very few estimates of these parameters have been published in any health risk prevention field (Murray and Blitstein, 2003; Murray et al., 2006; Murray et al., 2007; Moonseong and Leon, 2008; Spybrook et al., 2009). This study would use repeated measures multilevel models to obtain the first estimates of these parameters for planning longitudinal GRTs of school- based HIV prevention interventions. In all cases, models with and without adjustment for covariates would be analyzed to contribute information on the extent to which adjustment for covariates may reduce ICCs and needed sample size in school-based GRTs of HIV/STI prevention interventions. The effects of the various ICC and variance component estimates on the sample size needed to detect commonly seen effect sizes also would be examined. The results of this study would be made available through peer-reviewed articles and conference presentations in order to benefit researchers planning future school-based HIV/STI prevention studies. Efficient planning of these trials is critical given the importance of schools as a venue for delivering prevention interventions to adolescents and the costs associated with implementing school-based GRTs. PUBLIC HEALTH RELEVANCE: Schools are an important venue for HIV/STI prevention interventions because most youth attend schools, making them efficient sites for program delivery. Rigorous evaluation of these interventions is critical to ensure public health resources are applied to programs that have meaningful effects on the rates of HIV and other STIs in youth. The gold standard for rigorous evaluation of school-based HIV prevention interventions is the group randomized trial (GRT), but planning such trials with the sample size (number of schools/students) necessary for estimating intervention effects with adequate power and precision requires estimates of the intraclass correlation coefficient (ICC) parameter from studies involving similar outcomes, populations and settings. This project would provide the first ICC parameter estimates specific to HIV/STI-related behavioral and psychosocial outcomes across a variety of different school settings and populations so that researchers in the field could select the most appropriate ICCs for efficiently sizing these costly studies.