Establishing conversion of the 16-item Informant Questionnaire on Cognitive Decline in the Elderly scores into interval-level data across multiple samples using Rasch methodology
Truong, Quoc Cuong, Numbers, Katya, Choo, Carol C., Bentvelzen, Adam C., Catts, Vibeke S., Cervin, Matti, Jorm, Anthony F., Kochan, Nicole A., Brodaty, Henry, Sachdev, Perminder S., and Medvedev, Oleg N. (2023) Establishing conversion of the 16-item Informant Questionnaire on Cognitive Decline in the Elderly scores into interval-level data across multiple samples using Rasch methodology. Psychogeriatrics, 23 (3). pp. 411-421.
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Abstract
Background: The 16-item Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE-16) is a well-validated and widely-used measure of cognitive changes (CCs) among older adults. This study aimed to use Rasch methodology to establish psychometric properties of the IQCODE-16 and validate the existing ordinal-to-interval transformation algorithms across multiple large samples.
Methods: A Partial Credit Rasch model was employed to examine psychometric properties of the IQCODE-16 using data (n = 918) from two longitudinal studies of participants aged 57–99 years: the Older Australian Twins Study (n = 450) and the Canberra Longitudinal Study (n = 468), and reusing the Sydney Memory and Ageing Study (MAS) sample (n = 400).
Results: Initial analyses indicated good reliability for the IQCODE-16 (Person Separation Index range: 0.82–0.90). However, local dependency was identified between items, with several items showing misfit to the model. Replicating the existing Rasch solution could not reproduce the best Rasch model fit for all samples. Combining locally dependent items into three testlets resolved all misfit and local dependency issues and resulted in the best Rasch model fit for all samples with evidence of unidimensionality, strong reliability, and invariance across person factors. Accordingly, new ordinal-to-interval transformation algorithms were produced to convert the IQCODE-16 ordinal scores into interval data to improve the accuracy of its scores.
Conclusions: The findings of this study support the reliability and validity of the IQCODE-16 in measuring CCs among older adults. New ordinal-to-interval conversion tables generated using samples from multiple independent datasets are more generalizable and can be used to enhance the precision of the IQCODE-16 without changing its original format. An easy-to-use converter has been made available for clinical and research use.
| Item ID: | 78538 |
|---|---|
| Item Type: | Article (Research - C1) |
| ISSN: | 1479-8301 |
| Keywords: | cognitive changes, Informant Questionnaire on Cognitive Decline in the Elderly, measurement, Rasch analysis, reliability |
| Copyright Information: | © 2023 The Authors. Psychogeriatrics published by John Wiley & Sons Australia, Ltd on behalf of Japanese Psychogeriatric Society. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivsLicense, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. |
| Date Deposited: | 24 Oct 2023 04:39 |
| FoR Codes: | 52 PSYCHOLOGY > 5204 Cognitive and computational psychology > 520401 Cognition @ 100% |
| SEO Codes: | 20 HEALTH > 2005 Specific population health (excl. Indigenous health) > 200502 Health related to ageing @ 50% 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280112 Expanding knowledge in the health sciences @ 50% |
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