Gasser Theo, Rousson Valentin
Department of Biostatistics, Institute for Social and Preventive Medicine, University of Zürich, Sumatrastrasse 30, CH-8006 Zürich, Switzerland.
Stat Med. 2004 Dec 15;23(23):3641-53. doi: 10.1002/sim.1914.
Associated movements (AMs) are a classical diagnostic tool to assess differences between normal children and children with some motor dysfunction. This paper presents a methodology to produce age- and gender-dependent reference-curves for AMs of normal children, for various tasks of a test battery. Data available consist of separate ratings of duration and extent of AMs, which are ordinal quantities with few levels. Other problems are severe age- and gender-dependent floor-effects (as well as some ceiling-effects), leaving little information for analysis at older ages. To get a better scale, we combined the two ordinal ratings into one meaningful and quasi-continuous quantity referred to as intensity of AMs. In order to solve problems due to floor-effects, ceiling-effects and discreteness, we assumed left- , right- and interval-censored values, respectively. We considered a censored regression problem and postulated a truncated normal distribution for the non-censored values (after an appropriate transformation of the data). Using Wei and Tanner's poor man's data augmentation algorithm, together with the technique of linear mixed effects modelling, useful reference-curves could be produced. In contrast to the cumulative probabilities approach for ordinal data, our methodology allows the calculation of individual age- and gender-standardized values, which puts us in a position to investigate numerous scientific questions.
联合运动（AMs）是评估正常儿童与存在某些运动功能障碍儿童之间差异的经典诊断工具。本文提出了一种方法，可为正常儿童在一套测试组合的各种任务中的联合运动生成与年龄和性别相关的参考曲线。现有的数据由联合运动持续时间和幅度的单独评分组成，这些评分是具有少量等级的有序变量。其他问题包括严重的年龄和性别依赖性下限效应（以及一些上限效应），导致在较大年龄时可供分析的信息很少。为了获得更好的量表，我们将这两个有序评分合并为一个有意义的准连续量，称为联合运动强度。为了解决下限效应、上限效应和离散性问题，我们分别假设了左删失、右删失和区间删失值。我们考虑了一个删失回归问题，并对未删失值（在对数据进行适当变换后）假定了截断正态分布。使用魏和坦纳的简易数据扩充算法，结合线性混合效应建模技术，可以生成有用的参考曲线。与针对有序数据的累积概率方法不同，我们的方法允许计算个体年龄和性别标准化值，这使我们能够研究众多科学问题。
