Investigating psychometric properties of the Thai version of the Zarit Burden Interview using rasch model and confirmatory factor analysis.

OBJECTIVE: The Zarit Burden Interview (ZBI) has been widely used to assess caregiver burden. Few research papers have investigated the Thai version of the ZBI. The study aimed to examine the psychometric properties of the Thai version of both the full length (ZBI-22) and short versions (ZBI-12) using Rasch analysis and confirmatory factor analysis among a sample of Alzheimer's disease caregivers. RESULTS: The ZBI-22 fitted the Rasch measurement model regarding unidimensionality but not for ZBI-12. Five items from ZBI-22, and 2 items from ZBI-12 were shown to be misfitting items. Half of ZBI items were shown to be disordered category or threshold, and were locally dependent. CFA revealed three-factor and four-factor fitted the data the best for ZBI-22 and ZBI-12, respectively. Reliability was good for both forms of the ZBI (alpha = 0.86-0.92). Significant correlations were found with caregiver's perceived stress, anxiety/depression, pain and mobility but not with self-care and usual activity (p > 0.05), indicating convergent and discriminant validity. To conclude, the Thai version ZBI-22, but not ZBI-12, supported the reliability and unidimensional scale among Alzheimer's disease caregivers. Some misfitting items of the ZBI undermined the unidimensionality of the scale, and need revision.