Duarte Elisabeth Carmen, Garcia Leila Posenato, de Araújo Wildo Navegantes, Velez Maria P
Medical School, University of Brasilia- UnB, Brasília, Brazil.
Núcleo de Medicina Tropical, Campus Universitário Darcy Ribeiro, Asa Norte, Caixa Postal 4517, Brasília, DF, 70910-900, Brazil.
BMC Public Health. 2017 Dec 2;17(1):924. doi: 10.1186/s12889-017-4915-2.
Zika infection during pregnancy (ZIKVP) is known to be associated with adverse outcomes. Studies on this matter involve both rare outcomes and rare exposures and methodological choices are not straightforward. Cohort studies will surely offer more robust evidences, but their efficiency must be enhanced. We aim to contribute to the debate on sample selection strategies in cohort studies to assess outcomes associated with ZKVP. A study can be statistically more efficient than another if its estimates are more accurate (precise and valid), even if the studies involve the same number of subjects. Sample size and specific design strategies can enhance or impair the statistical efficiency of a study, depending on how the subjects are distributed in subgroups pertinent to the analysis. In most ZIKVP cohort studies to date there is an a priori identification of the source population (pregnant women, regardless of their exposure status) which is then sampled or included in its entirety (census). Subsequently, the group of pregnant women is classified according to exposure (presence or absence of ZIKVP), respecting the exposed:unexposed ratio in the source population. We propose that the sample selection be done from the a priori identification of groups of pregnant women exposed and unexposed to ZIKVP. This method will allow for an oversampling (even 100%) of the pregnant women with ZKVP and a optimized sampling from the general population of pregnant women unexposed to ZIKVP, saving resources in the unexposed group and improving the expected number of incident cases (outcomes) overall.
We hope that this proposal will broaden the methodological debate on the improvement of statistical power and protocol harmonization of cohort studies that aim to evaluate the association between Zika infection during pregnancy and outcomes for the offspring, as well as those with similar objectives.
已知孕期寨卡病毒感染（ZIKVP）与不良结局相关。关于这一问题的研究涉及罕见结局和罕见暴露，方法选择并非易事。队列研究肯定会提供更有力的证据，但其效率必须提高。我们旨在为关于队列研究中样本选择策略的辩论做出贡献，以评估与ZIKVP相关的结局。如果一项研究的估计更准确（精确且有效），那么即使研究涉及的受试者数量相同，它在统计学上也可能比另一项研究更有效。样本量和特定设计策略会增强或削弱研究的统计效率，这取决于受试者在与分析相关的亚组中的分布情况。在迄今为止的大多数ZIKVP队列研究中，事先确定了源人群（孕妇，无论其暴露状态如何），然后对其进行抽样或全部纳入（普查）。随后，根据暴露情况（是否感染ZIKVP）对孕妇群体进行分类，同时保持源人群中暴露组与非暴露组的比例。我们建议从事先确定的感染和未感染ZIKVP的孕妇群体中进行样本选择。这种方法将允许对感染ZIKVP的孕妇进行过度抽样（甚至100%），并从未感染ZIKVP的孕妇总体中进行优化抽样，从而在未暴露组节省资源，并总体上增加预期的发病例数（结局）。
我们希望这一提议将拓宽关于提高统计效力和使队列研究方案协调一致的方法学辩论，这些队列研究旨在评估孕期寨卡病毒感染与后代结局之间的关联，以及那些具有类似目标的研究。
