Background: Assessing arm and hand function of multiple sclerosis (MS) patients is important as impaired functioning may impact daily activities and reduce quality of life.
Objective: A short-form of the Arm Function in Multiple Sclerosis Questionnaire (AMSQ), a recently developed patient-reported outcome measure containing 31 items, is developed to allow non-adaptive application.
Methods: Complete data from 690 patients with MS, recruited via outpatient clinics, a residential center or via a Dutch website aimed at MS patients, were included in the analyses. A graded response model was fit to these data to estimate item response theory (IRT) parameters, which were used to perform post hoc computerized adaptive test (CAT) simulations with a cutoff standard error of measurement (SEM) of 0.32. The optimal test length was determined by the correlation between the static short-form and full-length theta, the mean SEM, and the amount of patients reaching a satisfactory SEM in CAT simulations.
Results and conclusion: Based on five selection criteria (i.e. discrimination parameters, total information, times selected in CAT simulations, raw item means, and item content), 10 items were selected for inclusion in the short-form. The score on the final 10-item short-form correlated strongly with the full-length AMSQ and provided reliable ability estimations, indicating its usefulness instrument in research and clinical settings.
Keywords: Arm Function in Multiple Sclerosis Questionnaire; computerized adaptive testing simulations; item response model; multiple sclerosis; psychometrics.