Devine O J, Smith J M
Radiation Studies Branch, Centers for Disease Control and Prevention, Atlanta, GA 30341-3724, USA.
Stat Med. 1998 Jun 30;17(12):1375-89. doi: 10.1002/(sici)1097-0258(19980630)17:12<1375::aid-sim857>3.0.co;2-d.
Sample size requirements for epidemiologic studies are usually determined on the basis of the desired level of statistical power. Suppose, however, that one is planning a study in which the participants' true exposure levels are unobservable. Instead, the analysis will be based on an imprecise surrogate measure that differs from true exposure by some non-negligible amount of measurement error. Sample size estimates for tests of association between the surrogate exposure measure and the outcome of interest may be misleading if they are based solely on the anticipated characteristics of the distribution of surrogate measures in the study population. We examine the accuracy of sample size estimates for cohort studies in which a continuous surrogate exposure measure is subject to either classical or Berkson measurement error. In particular, we evaluate the consequences of not adjusting the sample size estimation procedure for tests based on imprecise exposure measurements to account for anticipated differences between the distributions of the true exposure and the surrogate measure in the study population. As expected, failure to adjust for classical measurement error can lead to underestimation of the required sample size. Disregard of Berkson measurement error, however, can result in sample size estimates that exceed the actual number of participants required for tests of association between the outcome and the surrogate exposure measure. We illustrate this Berkson error effect by estimating sample size for a hypothetical cohort study that examines an association between childhood exposure to radioiodine and the development of thyroid neoplasms.
流行病学研究的样本量要求通常是根据所需的统计检验效能水平来确定的。然而，假设正在计划一项研究，其中参与者的真实暴露水平是不可观测的。相反，分析将基于一种不精确的替代测量方法，该方法与真实暴露之间存在一些不可忽略的测量误差。如果仅基于研究人群中替代测量分布的预期特征来估计替代暴露测量与感兴趣结局之间关联检验的样本量，可能会产生误导。我们研究了队列研究中样本量估计的准确性，在这些队列研究中，连续的替代暴露测量存在经典测量误差或伯克森测量误差。特别是，我们评估了在基于不精确暴露测量进行检验时，样本量估计程序未针对研究人群中真实暴露与替代测量分布之间的预期差异进行调整所产生的后果。不出所料，未对经典测量误差进行调整可能会导致所需样本量的低估。然而，忽视伯克森测量误差可能会导致样本量估计超过检验结局与替代暴露测量之间关联所需的实际参与者数量。我们通过估计一项假设队列研究的样本量来说明这种伯克森误差效应，该研究考察儿童期暴露于放射性碘与甲状腺肿瘤发生之间的关联。
