Intelligence testing in children with intellectual disabilities (ID) has significant limitations. The normative samples of widely used intelligence tests, such as the Wechsler Intelligence Scales, rarely include an adequate number of subjects with ID needed to provide sensitive measurement in the very low ability range, and they are highly subject to floor effects. The IQ measurement problems in these children prevent characterization of strengths and weaknesses, poorer estimates of cognitive abilities in research applications, and in clinical settings, limited utility for assessment, prognosis estimation, and planning intervention. Here, we examined the sensitivity of the Wechsler Intelligence Scale for Children (WISC-III) in a large sample of children with fragile X syndrome (FXS), the most common cause of inherited ID. The WISC-III was administered to 217 children with FXS (age 6-17 years, 83 girls and 134 boys). Using raw norms data obtained with permission from the Psychological Corporation, we calculated normalized scores representing each participant's actual deviation from the standardization sample using a z-score transformation. To validate this approach, we compared correlations between the new normalized scores versus the usual standard scores with a measure of adaptive behavior (Vineland Adaptive Behavior Scales) and with a genetic measure specific to FXS (FMR1 protein or FMRP). The distribution of WISC-III standard scores showed significant skewing with floor effects in a high proportion of participants, especially males (64.9%-94.0% across subtests). With the z-score normalization, the flooring problems were eliminated and scores were normally distributed. Furthermore, we found correlations between cognitive performance and adaptive behavior, and between cognition and FMRP that were very much improved when using these normalized scores in contrast to the usual standardized scores. The results of this study show that meaningful variation in intellectual ability in children with FXS, and probably other populations of children with neurodevelopmental disorders, is obscured by the usual translation of raw scores into standardized scores. A method of raw score transformation may improve the characterization of cognitive functioning in ID populations, especially for research applications.

中文翻译：

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智力障碍儿童认知测试局限性的解决方案：脆性 X 综合征案例。

智力障碍 (ID) 儿童的智力测试有很大的局限性。广泛使用的智力测试的规范样本，例如韦克斯勒智力量表，很少包括足够数量的 ID 受试者，以在非常低的能力范围内提供敏感的测量，并且它们很容易受到地板效应的影响。这些儿童的 IQ 测量问题妨碍了对优势和劣势的表征，在研究应用中对认知能力的估计较差，在临床环境中，评估、预后估计和计划干预的效用有限。在这里，我们在大量患有脆性 X 综合征 (FXS) 的儿童样本中检查了韦氏儿童智力量表 (WISC-III) 的敏感性，这是遗传 ID 的最常见原因。WISC-III 用于 217 名 FXS 儿童（6-17 岁，83 名女孩和 134 名男孩）。使用经心理公司许可获得的原始规范数据，我们使用 z 分数转换计算了代表每个参与者与标准化样本的实际偏差的标准化分数。为了验证这种方法，我们将新的标准化分数与通常的标准分数之间的相关性与适应性行为的测量（Vineland 适应性行为量表）和特定于 FXS（FMR1 蛋白或 FMRP）的遗传测量进行了比较。WISC-III 标准分数的分布显示，在高比例的参与者中，尤其是男性（子测试中为 64.9%-94.0%）存在显着的地板效应偏差。使用 z-score 归一化，消除了地板问题，分数呈正态分布。此外，我们发现认知表现和适应性行为之间以及认知和 FMRP 之间的相关性，与通常的标准化分数相比，当使用这些标准化分数时，这些相关性得到了极大的改善。这项研究的结果表明，通常将原始分数转换为标准化分数的做法掩盖了 FXS 儿童以及其他神经发育障碍儿童群体智力方面的有意义的变化。原始分数转换方法可以改善 ID 人群中认知功能的特征，尤其是对于研究应用。与通常的标准化分数相比，使用这些归一化分数时，认知和 FMRP 之间的关系得到了很大改善。这项研究的结果表明，通常将原始分数转换为标准化分数的做法掩盖了 FXS 儿童以及其他神经发育障碍儿童群体智力方面的有意义的变化。原始分数转换方法可以改善 ID 人群中认知功能的特征，尤其是对于研究应用。与通常的标准化分数相比，使用这些归一化分数时，认知和 FMRP 之间的关系得到了很大改善。这项研究的结果表明，通常将原始分数转换为标准化分数的做法掩盖了 FXS 儿童以及其他神经发育障碍儿童群体智力方面的有意义的变化。原始分数转换方法可以改善 ID 人群中认知功能的特征，尤其是对于研究应用。被通常将原始分数转换为标准化分数所掩盖。原始分数转换方法可以改善 ID 人群中认知功能的特征，尤其是对于研究应用。被通常将原始分数转换为标准化分数所掩盖。原始分数转换方法可以改善 ID 人群中认知功能的特征，尤其是对于研究应用。