Sauzet Odile, Ofuya Mercy, Peacock Janet L
Epidemiology and International Public Health, School of Public Health, Universität Bielefeld, Bielefeld, Germany.
Division of Health and Social Care Research King's College London and NIHR Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trust and King's College London, London, UK.
BMC Med Res Methodol. 2015 Apr 24;15:40. doi: 10.1186/s12874-015-0028-8.
Dichotomisation of continuous outcomes has been rightly criticised by statisticians because of the loss of information incurred. However to communicate a comparison of risks, dichotomised outcomes may be necessary. Peacock et al. developed a distributional approach to the dichotomisation of normally distributed outcomes allowing the presentation of a comparison of proportions with a measure of precision which reflects the comparison of means. Many common health outcomes are skewed so that the distributional method for the dichotomisation of continuous outcomes may not apply.
We present a methodology to obtain dichotomised outcomes for skewed variables illustrated with data from several observational studies. We also report the results of a simulation study which tests the robustness of the method to deviation from normality and assess the validity of the newly developed method.
The review showed that the pattern of dichotomisation was varying between outcomes. Birthweight, Blood pressure and BMI can either be transformed to normal so that normal distributional estimates for a comparison of proportions can be obtained or better, the skew-normal method can be used. For gestational age, no satisfactory transformation is available and only the skew-normal method is reliable. The normal distributional method is reliable also when there are small deviations from normality.
The distributional method with its applicability for common skewed data allows researchers to provide both continuous and dichotomised estimates without losing information or precision. This will have the effect of providing a practical understanding of the difference in means in terms of proportions.
连续型结局的二分法一直受到统计学家的合理批评，因为会导致信息丢失。然而，为了传达风险比较，二分法结局可能是必要的。皮科克等人开发了一种用于正态分布结局二分法的分布方法，允许以反映均值比较的精度度量来呈现比例比较。许多常见的健康结局呈偏态分布，因此连续型结局的分布二分法可能并不适用。
我们提出一种为偏态变量获取二分法结局的方法，并以多项观察性研究的数据为例进行说明。我们还报告了一项模拟研究的结果，该研究测试了该方法对偏离正态性的稳健性，并评估了新开发方法的有效性。
综述表明，二分法模式在不同结局之间存在差异。出生体重、血压和体重指数可以进行正态转换，以便获得用于比例比较的正态分布估计值，或者更好的是，可以使用偏态正态方法。对于孕周，没有可用的满意转换方法，只有偏态正态方法可靠。当与正态性有小的偏差时，正态分布方法也是可靠的。
该分布方法适用于常见的偏态数据，使研究人员能够提供连续和二分法估计值，而不会丢失信息或精度。这将有助于从比例角度实际理解均值差异。
