Measurement properties of the Arm Function in Multiple Sclerosis Questionnaire (AMSQ): a study based on Classical Test Theory.

Purpose: The construct validity, test-retest reliability, and measurement error of the Arm Function in Multiple Sclerosis Questionnaire (AMSQ) were examined. Additionally, the influence of administrationmethod on reliability and measurement error was investigated. Method: 112 Dutch adult MS-patients from an academic- and a residential care-facility participated. Questionnaires were administered on paper, online or as interview, and patients performed several performance tests. Construct validity was assessed by testing pre-defined hypotheses. Reliability was assessed using Intraclass Correlation Coefficients (ICCs), Standard Error of Measurements (SEMs) and Smallest Detectable Changes (SDCs). Results: For construct validity (N=105) 9 of 13 hypotheses were confirmed (69%). As expected, the AMSQ showed moderate to strong relationships with the instruments measuring similar constructs. The test-retest reliability coefficient was 0.96 (95% Confidence Interval 0.94-0.97); SEM was 6.3 (6.3% of scale range); SDC was 17.5 (on a sale from 0 to 100). Different administration-methods showed good reliability (ICC 0.88-0.94) and small standard errors (SEM 5.6-7.2). Conclusion: The AMSQ shows satisfying results for validity and excellent reliability; allowing for proper use in research. Due to a large SDC value, caution is needed when using the AMSQ in individual patient care. Further research should determine whether the SDC is smaller than the minimal important change. [ABSTRACT FROM AUTHOR]