Development of a Computerized Adaptive Testing System of the World Health Organization Disability Assessment Schedule 2.0 (CAT-WHODAS 2.0) for People With Dementia.

Importance: Widely used for assessing levels of disability, the World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) provides informative profiles for six life perspectives. However, its utility is constrained by its lengthy assessment time, decreasing respondents' willingness to complete it.

Objective: To address the utility challenge by developing a computerized adaptive testing system of the WHODAS 2.0 (CAT-WHODAS 2.0) for people with dementia.

Design: Fit indices were analyzed for a multidimensional Rasch model. The consistency of item difficulties was examined for the score comparability for examinees across sexes. The best set of stopping rules was determined using simulations to achieve high reliability and efficiency simultaneously.

Setting: Community.

Participants: The responses of 3,124 people were obtained from a nationwide database for disability certification, assessed through interviews.

Results: Twenty-seven items exhibited satisfactory model fits (infit and outfit mean squares = .58-1.35), and no items demonstrated differential item functioning by sex (difference values = -0.07 to 0.04). With the best set of rules, the CAT-WHODQAS 2.0 required approximately nine items to provide high Rasch person reliabilities in the six domains. These reliabilities were similar to those of the item bank (.90-.91 versus .93-.96). The concurrent validity was excellent: Pearson's rs = .90-.94 with the raw domain scores and .96-.99 with item bank.

Conclusions and relevance: The CAT-WHODAS 2.0 can provide efficient, reliable, valid, and sex-unbiased assessments of disability for people with dementia. It may serve as an alternative for clinicians and researchers to optimize the efficiency of data collection. Plain-Language Summary: This article presents the computed adaptive testing of the World Health Organization Disability Assessment Schedule 2.0 (CAT-WHODAS 2.0) as an efficient solution to provide reliable, valid, and sex-unbiased assessments of disability among people with dementia. The CAT-WHODAS 2.0 is a promising alternative for clinicians because it can efficiently assess a person's level of disability with extremely high reliabilities in the six domains of functioning (cognition, mobility, self-care, getting along, life activities, and participation). The CAT-WHODAS 2.0 is also useful for researchers because its scores are comparable with those of the item bank, which consists of 27 items calibrated by the Rasch model.