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

Abstract

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.

The sensitivity to change over time of the Amsterdam IADL Questionnaire©

“…Executive functioning is measured by Trail Making Test B, where performance is given by the amount of minutes required for completion. After the previous validation studies of Sikkes et al [4,5], where good construct validity, good content validity, and high internal consistency were demonstrated, this is the first study on the sensitivity to change of the A-IADL-Q. Also, this is the first study to assess the responsiveness of an IADL instrument by the construct approach, which is the recommended approach in the absence of a gold standard [8].…”

“…Third, in this study the mood of the patient and informant, which could potentially have an effect on measures of daily functioning, was not assessed. However, a previous study by Sikkes et al [5] showed the correlation of the A-IADL-Q with depressive symptoms of both the patient and the informant to be low. Therefore, do not expect these factors to have a significant influence on A-IADL-Q scores in this study.…”

“…In this case, the construct is IADL functioning, ranging from disability to ability. The total score is normally distributed (M 5 50, SD 5 10), with higher scores indicating better functioning [5]. Good construct validity, good content validity, high internal consistency (IRT reliability coefficient: .97), and high testretest reliability (87.9% of the items had kappa values ..60) were demonstrated previously [4,5].…”

“…Unfortunately, most of the questionnaires that measure IADL are not up-to-date and lack information about important measurement properties [3]. Therefore, Sikkes et al [4] has developed the informant-based Amsterdam IADL Questionnaire Óa , which has shown to be a reliable and valid instrument in the evaluation of dementia [4,5].…”

Delays in Manual Reaching Are Associated with Impaired Functional Abilities in Early Dementia Patients

“…Therefore, we do not think that this issue might have affected our results. We do suggest that future studies explore the possibility to use more elaborate ADL and IADL function tests [29,30] to further elucidate the role of impaired eye-hand coordination in developing functional disability. Finally, in this study we used a combination of an eye tracking system, a motion detection system, and a touch screen to quantify characteristics of eye-hand coordinated movements.…”