Sonja Mensch

103 Construct validity and responsiveness DISCUSSION This 18-month prospective cohort study was one of the initial prospective studies in children with SMD with adequate participant sample size. It was designed to obtain first data on validity of the Movakic instrument, a questionnaire-based instrument to monitor motor abilities in this specific group. The results show that Movakic has good construct validity and is significantly responsive to change resulting from events that impact motor ability such as surgery. The sample in this study reflects the complexity of the population in terms of the variety of comorbidities and events such as surgery, medication changes, or diseases that potentially influence motor abilities. Because of this complexity we could not evaluate Movakic’s responsivity to specific intervention effects. Therefore, we had to rely on whether or not Movakic scores of motor abilities were sensitive to events that were theorized to influence motor ability. In order to minimize confounding, therapists were instructed to score motor abilities they believed would be stable over time. Based on clinical experience we have tried to estimate the influence of meaningful events. The many events impacting these children over time will always complicate evaluation of intervention effects, both in clinical practice and in research. Therefore, intervention studies should examine the effects of botulinum toxin treatment, specific physical therapy interventions, orthopedic surgery or assistive devices. In clinical practice, careful information on unexpected events should be explicitly considered as part of the evaluation of motor ability. In addition, cohort studies of children with serious comorbid conditions may have a higher chance of loss to follow up. To this extent, we decided to add a standardized form to the Movakic instrument to note events and their potential implications for motor ability or lost to follow up. As almost half of the children with SMD in this study were diagnosed with CP we considered the Gross Motor Function Measure (GMFM) (Russell et al., 1989) to be used for these children. The GMFM is specifically developed for children with Cerebral Palsy and has also been used to create gross motor function growth curves for children with Down syndrome (Palisano et al., 2001). The study on clinical suitability of currently used instruments in practice (Mensch et al., 2015c) showed us that the GMFM scored low level of motor abilities and support by assistive devices was allowed. However, we note the following limitations in the suitability of using the GMFM in clinical practice for children with SMD: 1- the grading of scoring may not be sensitive to subtle changes in motor abilities; 2- the difficulty of testing motor abilities in unnatural settings, and 3- the difficulty of understanding and following directions when administering verbal instructions. These are some of the same concerns that lead to the development of the Movakic.