Reliability and Construct Validity of Three Self-report Questionnaires Assessing Dual-Task Difficulties in People With Multiple Sclerosis: An International Study.

Objective: To evaluate the reliability and validity of the dual-tasking questionnaire (DTQ), dual-task screening list (DTSL), and dual-task impact on daily life activities questionnaire (DIDA-Q).

Design: Multicenter, cross-sectional study SETTING: Persons with multiple sclerosis (pwMS) were recruited from 7 multiple sclerosis centers across 6 countries (Belgium, Chile, Italy, Israel, Spain, and Turkey).

Participants: A total of 356 pwMS (mean age 47.5±11.5y, expanded disability status scale, 3.79±1.83) were enrolled.

Interventions: Not applicable MAIN OUTCOME MEASURES: The reliability (internal consistency, test-retest, and measurement error) and construct validity (structural and convergent) were assessed.

Results: The DTQ, DTSL, and DIDA-Q demonstrated excellent test-retest reliability (intraclass correlation coefficients [95% CI], 0.84 [0.80-0.87] to 0.90 [0.87-0.92]) and internal consistency (Cronbach α: 0.86-0.96). As hypothesized, the 3 questionnaires showed a strong correlation with each other, moderate-to-strong correlations with other self-report questionnaires (perceived walking difficulties, fatigue, and fear of falling), and low-to-moderate correlations with cognitive information processing speed, manual dexterity, and dual-task walking performance (walking with word list generation task), showing convergent validity. The DIDA-Q exhibited systematically superior properties. These results were also verified in subsets from 6 different countries. In the structural validity analysis, all questionnaires displayed 2 main factors, allocated as "motor-driven" and "cognitive-driven" subscales.

Conclusions: The DTQ, DTSL, and DIDA-Q have good-to-excellent measurement properties, with the highest properties observed in DIDA-Q. The use of these self-reported questionnaires can be used in research and clinical practice to assess the effect of dual-task difficulties on the daily life of ambulatory pwMS.