Supplementary Material for: Validation of the Amsterdam IADL Questionnaire©, a New Tool to Measure Instrumental Activities of Daily Living in Dementia

Background: This study describes the validation of a new instrument measuring instrumental activities of daily living (IADL), the Amsterdam IADL Questionnaire© (a registered copyright of the Alzheimer Center of the VU University Medical Center). This informant-based tool aimed at detecting IADL problems in incipient dementia was previously found to have a high internal consistency and test-retest reliability. Methods: Patients and their informants who visited the Alzheimer Center of the VU University Medical Center were included in this study. Item response theory was used to estimate the individuals' trait levels as a measure of IADL disability. Construct validity was tested by correlating estimated trait levels with clinical and demographic measures using Pearson's or Kendall's τ correlation coefficients. Additionally, estimated trait levels between patients with and without dementia and between patients with early- and late-onset dementia were compared using independent t tests. Results: A total of 206 informants of patients completed the Amsterdam IADL Questionnaire. The correlations between estimated trait levels and other measures were in concordance with previously formed hypotheses. Patients diagnosed with dementia (n = 93) had higher estimated trait levels than patients without dementia (n = 96), Cohen's effect size, d = 1.04, t(187) = 7.1, p < 0.001. We found no differences between early- and late-onset dementia patients. Conclusions: Results suggest that the Amsterdam IADL Questionnaire is a reliable and valid instrument in the evaluation of dementia.

背景：本研究旨在验证一种新的测量日常生活活动能力（IADL）的量表——阿姆斯特丹IADL问卷©（阿姆斯特丹VU大学医学中心阿尔茨海默病中心的注册版权）。此基于信息提供者的工具旨在检测初期痴呆症患者的IADL问题，此前研究表明其具有较高的内部一致性和重测信度。方法：本研究纳入了访问VU大学医学中心阿尔茨海默病中心的病患及其信息提供者。通过项目反应理论估计个体特征水平，作为IADL功能障碍的测量指标。通过Pearson或Kendall的τ相关系数将估计的特征水平与临床和人口统计学指标进行相关性检验，以测试结构效度。此外，使用独立t检验比较了痴呆症患者和无痴呆症患者，以及早期和晚期痴呆症患者之间的估计特征水平。结果：共有206位病患信息提供者完成了阿姆斯特丹IADL问卷。估计特征水平与其他指标之间的相关性符合先前形成的假设。诊断为痴呆症的病患（n=93）的估计特征水平高于无痴呆症的病患（n=96），Cohen效应量，d=1.04，t(187)=7.1，p<0.001。我们未发现早期和晚期痴呆症患者之间存在差异。结论：结果表明，阿姆斯特丹IADL问卷是评估痴呆症的一种可靠且有效的工具。